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  1. 1 About AppStream
  2. 2 Upstream Metadata
  3. 3 Catalog Metadata
  4. 4 Miscellaneous
  5. 5 Metadata Quickstart
  6. 6 Data Validation
  7. 7 Manual pages
      appstreamcli 2012-2024Matthias Klumpp AppStream 26 July,2012 appstreamcli1appstreamcliHandle AppStream metadata formats and query AppStream dataappstreamcliCOMMANDDescription This manual page documents briefly the appstreamcli command. appstreamcli is a small helper tool to work with AppStream metadata and access the AppStream component index from the command-line. The AppStream component index contains a list of all available software components for your distribution, matched to their package names. It is generated using AppStream XML or Debian DEP-11 data, which is provided by your distributor. For more information about the AppStream project and the other components which are part of it, take a look at the AppStream pages at Freedesktop.org. Optionsget IDGet a component from the metadata pool by its identifier.ssearch TERMSearch the AppStream component pool for a given search term.what-provides TYPE TERM Return components which provide a given item. An item type can be specified using the TYPE parameter, a value to search for has to be supplied using the TERM parameter. Examples: Get components which handle the "text/xml" mediatype. appstreamcli what-provides mediatype "text/xml" Get component which provides the "libfoo.so.2" library. appstreamcli what-provides lib libfoo.so.2 refreshrefresh-cache Trigger a database refresh, if necessary. In case you want to force the database to be rebuilt, supply the --force flag. This command must be executed with root permission.status Display various information about the installed metadata and the metadata cache. os-info Show information about the current operating system from the metadata index. This requires the operating system to provide a operating-system component for itself. dump ID Dump the complete XML descriptions of components with the given ID that were found in the metadata pool. validate FILES Validate AppStream XML metadata for compliance with the specification. Both XML metadata types, upstream and distro XML, are handled. The format type which should be validated is determined automatically. The --pedantic flag triggers a more pedantic validation of the file, including minor and style issues in the report. validate-tree DIRECTORY Validate AppStream XML metadata found in a file-tree. This performs a standard validation of all found metadata, but also checks for additional errors, like the presence of .desktop files and validity of other additional metadata. check-license LICENSE Test a license string or license expression for validity and display details about it. This will check whether the license string is considered to be valid for AppStream, and return a non-zero exit code if it is not. The command will also display useful information like the canonical ID of a license, whether it is suitable as license for AppStream metadata, and whether the license is considered to be for Free and Open Source software or proprietary software. AppStream will consider any license as Free and Open Source that is marked as suitable by either the Free Software Foundation (FSF), Open Source Initiative (OSI) or explicit license list of the Debian Free Software Guidelines (DFSG). install ID Install a software component by its ID using the package manager or Flatpak. This resolves the AppStream component ID to an installation candidate and then calls either the native package manager or Flatpak (if available) to install the component. remove ID Uninstall a software component by its ID using the package manager or Flatpak. This will uninstall software matching the selected ID using either the native package manager or Flatpak (if available). put FILE Install a metadata file into the right directory on the current machine. compare-versionsvercmp VER1 [CMP] VER2 Compare two version numbers. If two version numbers are given as parameters, the versions will be compared and the comparison result will be printed to stdout. If a version number, a comparison operator and another version number are passed in as parameter, the result of the comparison operation will be printed to stdout, and appstreamcli will exit with a non-zero exit status in case the comparison failed. The comparison operator can be one of the following: eq - Equal tone - Not equal tolt - Less thangt - Greater thanle - Less than or equal toge - Greater than or equal tonew-template TYPE FILE Create a metainfo file template to be used by software projects. The --from-desktop option can be used to use a .desktop file as template for generating the example file. The generated files contain example entries which need to be filed in with the actual desired values by the project author. The first TYPE parameter is the name of an AppStream component type. For a complete list check out the documentation or the help output of appstreamcli for this subcommand. make-desktop-file MI_FILE DESKTOP_FILE Create a XDG desktop-entry file from a metainfo file. If the desktop-entry file specified in DESKTOP_FILE already exists, it will get extended with the new information extracted from the metainfo file. Otherwise a new file will be created. This command will use the first binary mentioned in a provides tag of the component for the Exec= field of the new desktop-entry file. If this is not the desired behavior, the --exec flag can be used to explicitly define a binary to launch. Other methods of launching the application are currently not supported. In order to generate a proper desktop-entry, this command assumes that not only the minimally required tags for an AppStream component are set, but also that it has an <icon/> tag of type "stock" to describe the stock icon that should be used as well as a <categories/> tag containing the categories the application should be placed in. news-to-metainfo NEWS_FILE MI_FILE [OUT_FILE] This command converts a NEWS file as used by many open source projects into the XML used by AppStream. Since NEWS files are free text, a lot of heuristics will be applied to get reasonable results. The converter can also read a YAML version of the AppStream release description and convert it to XML as well. If the metainfo file MI_FILE already exists, it will be augmented with the new release entries, otherwise the release entries will be written without any wrapping component. If [OUT_FILE] is specified, instead of acting on MI_FILE the changed data will be written to the particular file. If any of the output filenames is set to "-", the output will instead be written to stdout. The --format option can be used to enforce reading the input file in a specific format ("text" or "yaml") in case the format autodetection fails. The --limit option is used to limit the amount of release entries written (the newest entries will always be first). metainfo-to-news MI_FILE NEWS_FILE This command reverses the news-to-metainfo command and writes a NEWS file as text or YAML using the XML contained in a metainfo file. If NEWS_FILE is set to "-", the resulting data will be written to stdout instead of to a file. The --format option can be used to explicitly specify the output format ("yaml" or "text"). If it is not set, appstreamcli will guess which format is most suitable. convert FILE1 FILE1 Converts AppStream XML metadata into its YAML representation and vice versa. compose Composes an AppStream metadata catalog from a directory tree with metainfo files. This command is only available if the org.freedesktop.appstream.compose component is installed. See appstreamcli-compose1 for more information. --detailsPrint out more information about a found component.--no-colorDon't print colored output.--no-netDo not access the network when validating metadata. The same effect can be achieved by setting the AS_VALIDATE_NONET environment variable before running appstreamcli. --versionDisplay the version number of appstreamcliSee Alsopkcon1.AUTHOR This manual page was written by Matthias Klumpp matthias@tenstral.net. appstreamcli compose 2020-2024Matthias Klumpp AppStream 28 Aug,2020 appstreamcli compose1appstreamcli-composeCompose AppStream metadata catalog from directory treesappstreamcli composeCOMMANDDescription This manual page documents briefly the appstreamcli compose command. The appstreamcli compose tool is used to construct AppStream metadata catalogs from directory trees. The tool will also perform many related metadata generation actions, like resizing icons and screenshots and merging in data from referenced desktop-entry files as well as translation status information. Therefore, the tool provides a fast way to test how the final processed metadata for an application that is shipped to users may look like. It also provides a way to easily generate AppStream data for projects which do not need a more complex data generator like appstream-generator. In order for the appstreamcli compose command to be available, you may need to install the optional compose module for appstreamcli first. For more information about the AppStream project and the other components which are part of it, take a look at the AppStream pages at Freedesktop.org. OptionsSOURCE-DIRECTORIES A list of directories to process needs to be provided as positional parameters. Data from all directories will be combined into one output namespace. --origin NAME Set the AppStream data origin identifier. This can be a value like "debian-unstable-main" or "flathub". --result-root DIR Sets the directory where all generated output that is deployed to a user's machine is exported to. If this parameter is not set and we only have one directory to process, we use that directory as default output path. If both --data-dir and --icons-dir are set, --result-root is not necessary and no data will be written to that directory. --data-dir DIR Override the directory where the generated AppStream metadata catalog will be written to. Data will be written directly to this directory, and no supdirectories will be created (unlike when using --result-root to set an output location). --icons-dir DIR Override the directory where the cached icons are exported to. --hints-dir DIR Set a directory where hints reported generated during metadata processing are saved to. If this parameter is not set, no HTML/YAML hint reports will be saved. --media-dir DIR If set, creates a directory with media content (icons, screenshots, ...) that can be served via a webserver. The metadata will be extended to include information about these remote media. --media-baseurl URL The URL under which the contents of a directory set via --media-dir will be served. This value must be set if a media directory is created. --prefix DIR Set the default prefix that is used in the processed directories. If none is set explicitly, /usr is assumed. --print-report MODE Print the issue hints report (that gets exported as HTML and YAML document when --hints-dir was set) to the console in text form. Various print modes are supported: on-error only prints a short report if the run failed (default), short generates an abridged report that is always printed and full results in a detailed report to be printed. --no-partial-urls If set, all URLs in the generated data will be absolute and media_baseurl will not be used. This makes changing the media mirror harder without regenerating all data and is generally not recommended, to increase flexibility. --icon-policy POLICY-STRING Override the existing icon policy with a custom one. The icon policy sets how icons of different sizes should be dealt with. They can be in the icon cache only, be a remote icon in the media location or be both cached and available in the remote location. The icon-policy string is comprised of comma-separated %{size}x%{size}@%{scale}=%{state} statements. The size and scale are that of the respective icon, with the scale being allowed to be omitted if it is 1. The state can be one of remote, cached or cached-remote. By default, a policy of 48x48=cached,48x48@2=cached,64x64=cached,64x64@2=cached,128x128=cached-remote,128x128@2=cached-remote is selected. --allow-custom CUSTOM-KEY-NAMES By default, all custom entries set in MetaInfo input data are removed. This flag allows to whitelist custom keys to be propagated to the final catalog output data. The custom-key names should be provided as a comma-separated list. --components COMPONENT-IDs Set a comma-separated list of AppStream component IDs that should be considered for the generated metadata. All components that exist in the input data but are not mentioned in this list will be ignored for the generated output. --no-colorDon't print colored output.--verboseDisplay extra debugging information--versionDisplay the version number of appstreamcli composeSee Also appstreamcli1, appstream-generator1. AUTHOR This manual page was written by Matthias Klumpp matthias@tenstral.net.
  8. 8 AppStream API Reference
  9. Index
Applies to AppStream 1.0

2 Upstream Metadata

AppStream allows upstream projects to define metadata about the components they provide using small XML files, metainfo files, which get installed into locations on the client system and are used by distribuors to enhance their metadata.

A "component" is a piece of software, like an application, a library, a font or a codec. For several components, especially those which are shown in software-centers, we provide specialized metainfo files to define specific properties and data of these components. For example, applications and fonts support screenshots, while codecs don't.

All metainfo files need to contain a minimal amount of information, defined in the "Generic Component" section, which also describes some optional elements which can be used. Specialized components might require more information to be complete and valid.

The XML in metainfo files does not need any XML namespace, and adding one should generally be avoided. If you want to use a namespace though (maybe in case you want to embed the data in other contexts), the xmlns should be https://specifications.freedesktop.org/metainfo/1.0.

2.1 Generic Component

2.1.1 Introduction

For a distribution, it is good to know more about the content of a package. Which public interfaces (libraries? Python modules?) does it provide? Does it contain codecs? Does it contain firmware? Fonts? An application? All of this information can be used to automatically install missing software or to offer users a choice on what they want to install from a software center.

To provide this information, we created the metainfo files, which allow upstream projects to describe the content of their software package. If a metainfo file contains a <provides/> tag, distributors must also ensure that the package providing the file contains all items referenced by that statement, or is installed by a metapackage depending on packages which provide these items. This gives upstream projects a (very light) way to influence distributor packaging. More information about that can be found below.

Several specialized component-metainfo files exist, for example for applications or fonts. These are all based on this generic component XML specification, and are described in the following chapters.

2.1.2 Filesystem locations

Upstream projects can ship one or more metainfo files in /usr/share/metainfo/%{id}.metainfo.xml, where id is a unique identifier of this specific component.


Component metadata of type desktop-application as described in Section 2.3, “Desktop Applications” can be installed with an .appdata.xml extension as well for historical reasons. AppStream implementations will read the XML files as long as they end up in the right location on the filesystem.

Important: Legacy Path

AppStream tools scan the /usr/share/appdata/ path for legacy compatibility as well. It should not be used anymore by new software though, even on older Linux distributions (like RHEL 7 and Ubuntu 16.04 LTS) the metainfo path is well supported. Support for the legacy path will likely be dropped completely with a future AppStream 1.0 release.

2.1.3 XML Specification

The XML for a generic component definition starts with a <component> tag as the root element. The <component> element must at least have an id, name and summary tag; a provides tag with appropriate children is highly recommended.

In addition to the type attribute denoting the component type in case the component is not a generic component, the component tag may also have a date_eol attribute that sets a date when the component stops to be supported entirely (this may be the case for superseded legacy software like org.python.python2). The attribute value can be any complete date or time in ISO 8601 (https://en.wikipedia.org/wiki/ISO_8601).

All possible tags which can be used with components of all types are:


The id tag is a unique identifier for this component. It must contain only alphanumeric ASCII characters, dots, hyphens and underscores. Spaces are not allowed. While hyphens are allowed for legacy compatibility, their usage is strongly discouraged to ensure interoperability of the AppStream ID with other tools such as D-Bus (and thereby making the ID more generic and useful). For the same reason it is also strongly discouraged to start any segment of the ID with a digit. Additionally, even though uppercase letters are permitted in a component-ID, it is strongly encouraged to only use lowercase letters for the ID.

The ID must follow a reverse-DNS scheme, consisting of {tld}.{vendor}.{product}, for example org.kde.gwenview or com.hugski.colorhug2. Ownership of {vendor}.{tld} in the domain name system guarantees uniqueness of IDs.

To increase the uniqueness and to distinguish between different pieces of a software suite, it is suggested to append the type name to the component-id in these cases. For example, one can use com.hugski.colorhug2 for the client tools to control hardware, and com.hugski.colorhug2.firmware for the runtime firmware files.

Note that the value of this tag must be unique across all distributions and software deployment platforms. In case it is not unique, distributors are expected to reject the conflicting components from inclusion into their metadata and notify the upstream projects about this issue.

Important: Escaping characters in the component ID

To ensures the greatest possible compatibility of an AppStream ID, it is recommended to replace any hyphens in the ID in all but the last segment of it with underscores, and prefix every leading digit of a segment with an underscore as well. Since the underscore is not a valid character in domain names, the uniqueness of the ID is kept. For example, the ID org.7-zip.7-zip could become org._7_zip._7-zip.


The <metadata_license/> tag indicates the content license that you are releasing the one metainfo XML file under. This is typically not the same as the project license. Omitting the license value will result in the metainfo data not being incorporated into metadata collections as used by Linux distributions. This tag is required for all metainfo files.

The value of this tag has to be one of the recognized SPDX license IDs for <metadata_license/> tags, or a simple SPDX expression (only AND and OR operators allowed) allowing the use of the metadata file under one of the recognized licenses.

We do recognize a set of permissive (https://en.wikipedia.org/wiki/Permissive_software_licence) licenses that have been vetted for mutual compatibility. This is important in order to allow the metainfo metadata to be combined with arbitrary other data in one file. While copyleft licenses like the GPL are great for code, it is not feasible to test every copyleft license for mutual compatibility and compliance when combining metainfo metadata with other data into one larger assembly fully automatically.

Currently, the following licenses have been reviewed and can be used as metadata licenses:


  • MIT

  • 0BSD

  • CC0-1.0

  • CC-BY-3.0

  • CC-BY-4.0

  • CC-BY-SA-3.0

  • CC-BY-SA-4.0

  • GFDL-1.1

  • GFDL-1.2

  • GFDL-1.3

  • BSL-1.0

  • FTL


The license codes correspond to the identifiers found at the SPDX OpenSource License Registry (https://spdx.org/licenses/). For instance, CC-BY-SA-3.0 corresponds to the license at creativecommons.org/licenses/by-sa/3.0 (https://creativecommons.org/licenses/by-sa/3.0/). If you are looking for the simplest license to use for your metadata, using the FSFAP license is suggested.


A human-readable name for this software component. For example, if the component ID was "libc", its name might be "GNU Standard C Library".


A short summary of what this component does. If the component is "PackageKit", the summary could be "Provides a package-management abstraction layer". This element is translatable.


The <icon/> tag describes the component icon. It is mostly used for GUI applications (component-type desktop-application). It can be of type stock, local or remote.

stock icons are loaded from the icon stock (the current or hicolor/locolor fallback themes). The icon name must not include any file-extension or path.

local icons are loaded from a file in the filesystem. They should specify a full file path. This icon type may have width and height properties. If targeting a hi-DPI screen, this icon type may have a scale property.

remote icons loaded from a remote URL. Currently, only HTTP/HTTPS urls are supported. This icon type should have width and height properties. If targeting a hi-DPI screen, this icon type may have a scale property.

The semantics of each property in the <icon/> tag are the same as for the <icon/> tag for catalog metadata. See <icon/>.


A long description of this component. Some markup can be used.

Do not assume the format is HTML. This list contains all currently supported formatting options:

  • Paragraph (p)

  • Ordered list (ol), with list items (li)

  • Unordered list (ul), with list items (li)

  • Within paragraphs and list items, emphasis (em) and inline code (code) text styles are supported. The emphasis is commonly rendered in italic, while inline code is shown in a monospaced font.

  • Nested lists are not supported

In MetaInfo files, this tag should be translated by-paragraph. For enumerations, items are translated individually as well, and not the whole enumeration block. This means that in a translated file, only <p/> and <li/> elements may carry an xml:lang property.


This tag can contain one or more <category> entries, describing the categories this software component is associated with. This tag is usually applied to components of type desktop-application, but can be used with any component. A list of valid category names can be found in the Freedesktop menu specification (https://specifications.freedesktop.org/menu-spec/latest/apa.html). Example:


This tag can contain one or more <keyword> children, describing keywords for the component, to make it easier to find in a software center. For translated keywords in metainfo files, the individual keyword tags should be translated.


  <keyword translate="no">IDE</keyword>
  <keyword xml:lang="de">entwicklung</keyword>
  <keyword xml:lang="de">programmierung</keyword>

Defines web URLs for this component. There are several different URL types allowed:


Should be a link to the upstream homepage for the component.


Should point to the software's bug tracking system, for users to report new bugs.


Should link a FAQ page for this software, to answer some of the most-asked questions in detail, something which you cannot do in the component's description.


Should provide a web link to an online user's reference, a software manual or help page.


URLs of this type should point to a webpage showing information on how to donate to the described software project.


URLs of this type should point to a webpage where users can submit or modify translations of the upstream project.

Typically this should be a link to the project page in Weblate, Transifex or Zanata, but could also be a link to an upstream-hosted wiki page describing how to send translations upstream.


URLs of this type should allow the user to contact the developer.

This could for example be an HTTPS URL to an online form or a page describing how to contact the developer.


URLs of this type should point to a webpage on which the user can browse the sourcecode.


URLs of this type should point to a webpage showing information on how to contribute to the described software project.


This tag indicates possible methods to launch the software described in this component. It is allowed to appear multiple times in MetaInfo data.

The <launchable/> tag has a required type property indicating the system that is used to launch the component. The following types are allowed:


The application can be launched via a desktop file. The value of the tag is a desktop-file id (https://specifications.freedesktop.org/desktop-entry-spec/desktop-entry-spec-latest.html#desktop-file-id).

In case a software component has multiple launchable entries, the software center might display a dialog to choose which entry to launch. If possible though, it should be avoided to add multiple launchable tags of type desktop-id.


The software can be started, stopped, and monitored by the OS "init" facility, such as systemd. The value of the tag is a name that can be used with that facility, such as a systemd unit name.

Multiple launchable tags of type service are not alternatives to start the same service, but the component does contain multiple services that might all need to be started.

Only those services should be listed as launchables that the user is actually expected to start and stop manually. Services that are started/stopped indirectly via dependencies of other services should not be listed.

For systemd units, the services listed as launchables are expected to support enabling and disabling.


The software can be launched from the menus of the Cockpit (https://cockpit-project.org) admin interface. The value of the tag is the name of a Cockpit package (https://cockpit-project.org/guide/latest/packages.html).


The application is a web site that is viewed through a browser. The value of the tag is a direct HTTP/HTTPS URL that the browser must navigate to.


<launchable type="desktop-id">org.gnome.sysprof2.desktop</launchable>

The <releases> tag contains multiple release children that themselves contain metadata about releases made for this software component. The release information XML is described in-depth in Section 2.2, “Release Information”, examples for a valid releases tag with artifacts are also provided there.

Release information can be embedded in the component's metainfo file, following the XML description outlined in Section 2.2, “Release Information”. Alternatively, it can also be split into its own metadata file as described in that section. In case of external metadata, a releases tag must still be present in the component's metainfo file, and must have a type property set to value external (if the type property is missing, a value of embedded is implicitly assumed for it).

In case of external metadata, the releases tag may also have an url property linking to a web location where the release XML can be found and updated separately from the main component metadata. An url property must not be present without type set to external.

Only HTTPS links are allowed for the web URL, and any artifact defined in a release description from an external website should not be trusted without further verification, as external release information can currently not be signed.

AppStream catalog metadata generators may choose to update the locally provided release information with the data from the web location provided by the URL in url. This allow projects to complete release localization after a release was made, or include further information that was not yet available directly at release time. The generated catalog XML data must be complete and must not contain references to external release information.

Example for a releases block that points to an external metadata file:

<releases type="external" url="https://example.org/releases/org.example.myapp.releases.xml" />
Important: Local Release Data

Please note that even if release data is external and also provided on a remote location, it also must be available locally, installed as a file into /usr/share/metainfo/releases/%{cid}.releases.xml. The local file may not contain all information (for example it may not have a complete release description or all translations), but basic data such as the released versions and their release dates should be present.

It is an error to reference an external release data file, but not provide a local copy of it.


The provides tag and its children describe the public interfaces this application provides. A public interface can be anything which other applications, which are not part of the upstream project, can access or reference. This includes binaries and libraries. Private interfaces should never be added to a provides tag.

A provides tag contains a number of children describing the type and name of the provided public interface items. It is suggested that the build system auto-generates this tag and its children. Currently allowed item types are listed below. If you miss something, file a bug against AppStream (https://github.com/ximion/appstream/issues/new) so we can add the new type.


Describes the media types (also known as MIME types) this software supports, meaning it can open, edit or otherwise handle them. This tag is especially useful for generic components and addon-type components. For applications, the metadata may automatically be fetched from their .desktop files by the distribution's metadata generator if a desktop-entry file is set as <launchable/>. Example:


Contains the name of a shared library placed in a publicly accessible library path, such as /usr/lib, /usr/lib/<triplet> or /lib. For example, for the libappstream library, the value for library would be libappstream.so.1.


Name of a binary installed into a location in PATH.


Full name of a font provided by this component. See Section 2.8, “Fonts” for more information.


A modalias glob representing the hardware types (for example USB, PCI, ACPI, DMI) this component handles. Useful for installing printer drivers or other USB protocol drivers for smartphones, firmware, and out of tree kernel drivers.


This provided element is described in detail for the firmware component type, where it is mandatory. Please see <provides/> ↪ <firmware/> for more information.


Name of a Python 3 module this component provides.


Contains the well-known name of a D-Bus service as its value. The type of the service must be specified using the type property of this tag. Allowed values are user and system.


  <dbus type="system">org.freedesktop.packagekit</dbus>

Contains the component-ID of another software component. The presence of this tag indicates that the software component containing it is able to provide all functionality of the one referenced in the <provides/> ↪ <id/> tag.

This is useful in case a component-id had to be renamed in the past, e.g. because its domain-name changed.

<requires/>, <recommends/> & <supports/> 

The requires tag denotes an absolute requirement on a different entity. For example, a component can require certain hardware to be present, require a specific minimum kernel version, or another component to be installed first. If a requirement specified in a requires tag is not met, AppStream clients should prevent the installation of the particular software component.

If it is not essential that a certain requirement is met by the system, but just recommended to be available, a recommends tag should be used. In this case, AppStream clients should allow the installation of the software component, but may display a warning before allowing the installation. It is permissible, but not required, to prevent installation of software which does not have all items specified as recommends met on the system that it is installed to.

Components may also set a supports tag. This is an even weaker relation than recommends, and means the particular component can make use of certain hardware capabilities or other software if it is available, but will also be usable if it is not.

A requires, recommends or supports tag contains children describing the type, value and version relation of the required item. Each child can have a version and a compare property, to allow depending on a certain minimal version of the respective item. The version property contains the version to be compared against, while the compare property contains a two-letter code denoting how to compare the version of a present item with the version listed in the property. If no compare property is given, but a version property is found, AppStream implementations should implicitly assume a value of ge for comparison of the versions. The installed version is on the left side of the required version when comparing them. See Section 4.1, “Version Comparison Algorithm” for a description of the version comparison algorithm.

Possible two-letter codes for version comparisons are:

  • eq - Equal to

  • ne - Not equal to

  • lt - Less than

  • gt - Greater than

  • le - Less than or equal to

  • ge - Greater than or equal to

Please note that not all item types are valid for all relation types. Generally valid item types are listed below, with information as for which relation kins they are valid.


A relation to another software component. The value should be another component-ID. Example:

  <id version="1.0" compare="ge">org.example.my_software</id>

Valid for: requires, recommends, supports


Check for specific hardware to be present via its modalias. The modalias may contain a wildcard expression. Example:


Valid for: requires, recommends, supports


Check for a specific kernel to be running on the system. The kernel name is the output of uname -s. Example:

  <kernel version="4.14" compare="ge">Linux</kernel>

Valid for: requires, recommends


Set a relation to the amount of physical memory (RAM) the system should have to run the software component. The memory size is set in MiB. You usually only want to use this with the recommends tag, because users might want to install the software on systems even if they have a lesser amount of memory compared to what would be ideal. Example:

  <memory>2048</memory> <!-- recommend at least 2GiB of memory -->

Valid for: requires, recommends


Depend on a specific device firmware. The value of this tag should either be a name like bootloader, be empty to reference the firmware itself described by the firmware-type component this tag is contained in, or contain a GUID. This tag is commonly used and interpreted by the LVFS (https://fwupd.org/). Example:

  <firmware compare="ge" version="0.1.2">6de5d951-d755-576b-bd09-c5cf66b27234</firmware>
  <firmware compare="ge" version="0.1.2"/>
  <firmware compare="ge" version="0.3.4">bootloader</firmware>

Valid for: requires, recommends


Require, recommend or support a specific system hardware configuration. The value of this item is a Computer Hardware ID (CHID) (https://docs.microsoft.com/en-us/windows-hardware/drivers/dashboard/using-chids) without any surrounding braces.

On Linux systems, the CHIDs of the system can be queried using the sudo fwupdtool hwids command.

This tag is commonly used and interpreted by the LVFS (https://fwupd.org/) and fwupd tool. Example:


Valid for: requires, recommends, supports


This item type can be used to indicate support for or require certain ways a user can control the software. This usually maps to certain methods of input. If multiples control tags with different values are found within a requires/supports block, only one of them needs to be satisfied on the system to mark an application as compatible. This means if touch and pointing are both supported as controls for an application-type component, a system that only has a mouse and no touchscreen will still be considered able to run the application. Valid values for this tag are:

  • pointing - Input via mouse/cursors/other pointing devices is possible

  • keyboard - Keyboard input is possible

  • console - Control via a console / command-line interface

  • tablet - Graphics tablet input

  • touch - Input by touching a surface with fingers is possible

  • gamepad - The component supports gamepads (any game controller with wheels/buttons/joysticks)

  • tv-remote - Input via a TV remote (with arrow keys, number pad, other basic inputs) is supported.

  • voice - The software can be controlled via voice recognition/activation

  • vision - The software can be controlled by computer vision / visual object and sign detection

If a control type is supported (= in a supports block), it means the software supports the given method of user input. As long as one of the input methods is available on the system, the software can be used. Installation on systems without the given control may still be permitted, but the software may not be easily usable.

If a control type is recommended (= in a recommends block), it means the software prefers the given method of user input. The software may still be installed if the input control method is not available, but functionality may be severely degraded.

If a control type is required (= in a requires block), the same applies, but the software installer should refuse to install the software on devices which do not have at least one of the input methods. It is therefore advised to only use the control tag in supports and possibly recommends blocks, and avoid to use it in requires.

For certain component types, some permitted controls are implicitly assumed: For desktop-application and web-application components, pointing and keyboard controls are assumed supported, unless explicit support is defined by the metadata author. For console-application, control via console is assumed.

For any other, non-application-like component types, the control relation item is currently considered unsupported.

Example control support block:


Valid for: requires, recommends, supports


Set a relation to the display length defined as an integer value in logical pixels (device pixels divided by scaling factor, roughly equivalent to 0.26mm (1/96in), also known as device-independent pixels). Setting the side property to either shortest or longest will apply the selected size constraint to either the shortest or longest side of the display rectangle, with shortest being implicitly assumed if no value is set.

Note: About Pixel Dimensions

One logical pixel (= device independent pixel) roughly corresponds to the visual angle of one pixel on a device with a pixel density of 96dpi and a distance from the observer of about 52cm, making the physical pixel about 0.26mm in size. When using logical pixels as unit, they might not always map to exact physical lengths as their exact size is defined by the device providing the display. They do however accurately depict the maximum amount of pixels that can be drawn in the depicted direction on the device's display space.

Relations for the display length can be defined using a compare property as described in <requires/>, <recommends/> & <supports/>. If this property is not present, a value of ge (greater-or-equal) is implicitly assumed.

Note: Determining Device Types

Please note that a display with a lot of vertical space may not be a television screen, but could also be a large gaming monitor. Similar logic applies to the smaller screen sizes. Therefore, to indicate that an application runs well on a certain device and not just on a certain display, additional metadata is needed, like the application's supported input controls as defined via <control/>.

Note: Sizes for Reference

The sizes below are for reference if you do not know the exact dimensions your application will fit into, and just need a rough guideline as to what device type you can expect at a given size:

  • Very small screens, as used in watches, wearables and other small-display devices: about <= 360px

  • Small screens often used in handheld devices, such as phone screens, small phablets: about < 768px

  • Screens in laptops, tablets: about >= 768px

  • Bigger computer monitors: about >= 1024px

  • Television screens, large projected images: about >= 3840px

This tag may appear up to four times to set a minimum and maximum dimension required. If multiple displays are connected to a device, it is acceptable to test against either the largest screen attached to the device, or the combined amount of display space (depending on what makes the most sense for the respective device / setup). A software center application may test for the maximum possible resolution of an attached display, and not the currently set display resolution in case it wants to check against hardware capability and not be influenced by user configuration.

If used in a requires block, this relation can be used to restrict an application to only be installable on systems which have a minimum usable display length available for it. If used in a recommends block, the application will still be installable, but the user may be shown a warning.

If no display_length relation is present, a minimum required display (ge) relation of 768px is implicitly assumed to preserve backwards compatibility (so applications capable of running on smaller screens need to make their support for that configuration explicit).


<!-- recommend at least 600 logical pixels of space -->
  <display_length compare="ge">600</display_length>

<!-- ensure this application is not run on a very large screen, or
     very small screen (no tiny handhelds or television screens) -->
  <display_length compare="lt">3840</display_length>
  <display_length compare="gt">360</display_length>

Valid for: requires, recommends


Require, recommend or support connectivity to the internet. The value of this item one of the following:

  • always - Needs internet connectivity to work. If used in a recommends element, then this indicates that the app can work without internet, but the experience will be degraded.

  • offline-only - Never uses the internet, even if it’s available.

  • first-run - Uses the internet the first time the application is run, but not normally afterwards.

If the value of <internet/> is not offline-only, the bandwidth_mbitps attribute can be set to a bandwidth (in Mbit/s) which is the minimum internet bandwidth needed for the application to be usable. If this attribute is not set, it’s assumed that the application is usable with all internet connections.


<!-- always needs the internet -->

<!-- always needs the internet and has a degraded experience if it’s not at least 2Mbit/s -->
  <internet bandwidth_mbitps="2">always</internet>

<!-- never uses the internet, even if available -->

<!-- the software explicitly supports running offline (but may also be able to use online features) -->

<!-- requires the internet on first run -->

<!-- can work without the internet, but with a degraded experience -->

<!-- recommends the internet for when it’s first run, but can work without -->

<!-- requires the internet on first run, can run without it afterwards but with a degraded experience -->

Valid for: requires, recommends, supports


The replaces tag denotes indicates that the given component completely replaces another one on the system. In most cases, the replaced component and the one that replaces it can not be coinstalled. Compared to a <provides/>id relationship, for a replaced component there is no common interface that two components can provide at once.

A replaces tag has id children which have the component-IDs of the components that the current component replaces as value.

This feature is usually used for components that have to change their ID. While metainfo data may contain replaces tags, software repository providers should filter these tags carefully to ensure that the new component has the right to replace an old one.


<!-- the 7-zip application changes its ID and therefore replaces the component with its old ID -->

This tag can contain one or more <mimetype/> children, describing the MIME types this application supports.

Important: Deprecation

This tag is deprecated and should not be used for new metadata. Please use <provides/>mediatype tags instead.


If you include the <project_group/> tag then this identifies your project with a specific upstream umbrella project. Known values include GNOME, KDE, XFCE, MATE and LXDE, although other umbrella projects like Yorba or Mozilla make sense too.


You should only identify with an umbrella project if you use all their infrastructure and policies, for instance string freezes dates, bugtracker and source control instance.


The <compulsory_for_desktop> tag indicates that the component which the metadata belongs to is essential for the functionality of the defined desktop environment. Examples for compulsory components are the GNOME Shell by the GNOME Project, or the Plasma Desktop by KDE, as well as things like iBus or the desktop login manager.

Software centers are expected to detect the running desktop environment and disable uninstallation for compulsory components of that desktop, so users will not be able to damage their currently running, primary desktop environment.

Multiple occurrences of the <compulsory_for_desktop> tag are allowed, so a project can be essential for many desktops. The distributor decides which components should be made compulsory, however it is generally a good idea to follow upstream's recommendations on that matter.

A list of all allowed values for this tag is defined in the XDG Menu Specification (https://specifications.freedesktop.org/menu-spec/latest/apb.html). Software center applications will only recognize these values.


The <project_license/> tag is indicating the license of the component (application/library/addon/font/etc.) described in the metadata document. It should be an SPDX license expression (https://spdx.org/specifications). Please note the SPDX license IDs are case-sensitive in AppStream. Possible values include:

  • GPL-2.0

  • LGPL-3.0+ AND GPL-3.0+

  • MIT

  • CC-BY-SA-2.0

  • LicenseRef-proprietary=https://example.com/mylicense.html

A full list of recognized licenses and their identifiers can be found at the SPDX OpenSource License Registry (https://spdx.org/licenses/).

Custom licenses which are not in the SPDX registry, like proprietary licenses, can be denoted using the LicenseRef notation. LicenseRef-proprietary can be used to denote a proprietary license, with an optional URL to the license text following after a = sign.

The license given in the project_license tag should be the ‘main’ license of the project. For a software project, this is typically the license for the code. It is not recommended to include the license for accompanying documentation (for example) in project_license, as that could confuse users. In particular, the CC-BY-SA-3.0 license which is commonly used for documentation is not an (FSF or OSI) approved license for free software, so including it in project_license results in the project as a whole being considered non-free.

Although the project_license tag is not mandatory, it is highly recommended to include it.


<project_license>LGPL-3.0+ OR MPL-2.0</project_license>
<project_license>LGPL-3.0+ OR MPL-2.0</project_license>

The <developer/> element is designed to represent the developers or project responsible for development of the project described in the metadata. It must appear only once per component.

The element should have a id property, containing a unique ID to identify the component developer / development team. It is recommended to use a reverse-DNS name, like org.gnome or io.github.ximion, or a Fediverse handle (like @user@example.org) as ID to achieve a higher chance of uniqueness.

A developer element must have one name tag as child, which contains a translatable name for the component developer or development team. Values might be for example "The GNOME Foundation" or "The KDE Community". Hyperlinks or emails must not be used in the name; if you want to link to the developer's homepage, use the <url/>-tag instead. The name tag is translatable, it must only exist once in its untranslated form.


The <developer_name/> tag is designed to represent the developers or project responsible for development of the project described in the metadata.

Important: Deprecation

This tag is deprecated and should not be used for new metadata. Please use <developer/> instead.


Visual components (like fonts or graphical applications) may choose to add one or multiple screenshots to their metadata. Screenshots can be either a video or a static image.

The <screenshots/> tag contains multiple <screenshot/> children, where at least one of them must have the property type="default" to indicate the primary and most representative screenshot of the software.

Optionally, a screenshot may also have an environment property. This string property denotes the GUI environment the screenshot was recorded in, in the form of {env}:{style}, where {env} is a desktop-environment name in lowercase and {style} is a specific style that the desktop environment recognizes, e.g. light and dark for light and dark themes. See desktop-style-ids.txt (https://github.com/ximion/appstream/blob/main/data/desktop-style-ids.txt) for a list of currently recognized environment and style combinations.

Software centers displaying the component will usually prefer screenshots of the current environment and style, and display them first, even before the screenshot marked as default.

In general, screenshots should be displayed in the order the are defined in in their screenshots block for the respective component on a per-environment basis (all screenshots of the same environment/style will be displayed in the order they are listed in the XML, but may be moved to the front of the list as a whole depending on the current environment).

Every <screenshot/> element must have at least one <image/> or <video/> child, but never an image and video at the same time.

Screenshots containing videos must not be the default screenshot.

The value of the <image/> tag is a direct HTTP/HTTPS URL to a screenshot uploaded to a public location on the web. Images should ideally be provided in the PNG format; using JPEG or WebP is also permitted for images in metainfo files.

The <image/> tag may have the following properties:

  • type

    The type of the image: source for the source image, and thumbnail for a thumbnail image. In case the type is thumbnail, the width and height properties must be present.

  • width

    The width of the image in pixels.

  • height

    The height of the image in pixels.

  • scale

    A scaling factor for the image, if it is intended for a HiDPI display. If a scaling factor > 1 is set, the width/height values are not adjusted to scale. They always represent the exact image dimensions in pixels.

  • xml:lang

    The language this screenshot image is translated in. This property should only be present if there are multiple images with different locales present.

The value of the <video/> tag is a direct HTTP/HTTPS URL to a video uploaded to a public location on the web. The video must be in a Matroska (.mkv) (https://www.matroska.org/) or WebM (https://www.webmproject.org/) container and use either the VP9 (https://www.webmproject.org/vp9/) or AV1 (https://aomedia.org/av1-features/) codec. The video should ideally work without any audio, but if audio is needed, the Opus (https://opus-codec.org/) codec should be used. Software centers may still play the video without any sound though. Additionally, AppStream metadata repositories (like in distributions such as Fedora and Debian) may impose size limitations to video files delivered by their CDN, so it is recommended to keep the video file size below 10MiB. There is also a chance that software centers do not display any video at all, so a video must never be in a default screenshot.

The <video/> tag may have the following properties:

  • container

    The video container that is used, can be webm or matroska.

  • codec

    The video codec used, can be av1 or vp9.

  • width

    The width of the video in pixels.

  • height

    The height of the video in pixels.

  • xml:lang

    The language this video is translated in. This property should only be present if there are multiple videos with different locales present.

Optionally, a <screenshot/> tag may have a translatable <caption/> child, defining a short (ideally not more than 100 characters) description of what the user can see on the referenced screenshot.

A source video should be concise, easy to understand and not have an overly large file size. Try to use a reasonably large image for source images, as they may be scaled down to thumbnail images in metadata processing. It is suggested to have videos and images in 16:9 aspect ratio, as long as that is sensible for the displayed application.


  <screenshot type="default">
    <caption>The FooBar main window.</caption>
    <image type="source" width="1600" height="900">https://example.com/foobar/screenshot-1.png</image>
    <caption>Foobar showing the frobnicate functionality.</caption>
    <image type="source" width="1600" height="900">https://example.com/foobar/screenshot-2.png</image>
    <video codec="av1" width="1600" height="900">https://example.com/foobar/screencast.mkv</video>

  <screenshot environment="plasma-mobile">
    <caption>The FooBar main window, but on Plasma Mobile</caption>
    <image type="source" width="1600" height="900">https://example.com/foobar/screenshot-1_plasma-mobile.png</image>

  <screenshot environment="gnome:dark">
    <caption>The FooBar main window, on GNOME in dark mode</caption>
    <image type="source" width="1600" height="900">https://example.com/foobar/screenshot-1_gnome_dark.png</image>

The <translation/> tag is an optional tag which can be added to specify the translation domain used for this software component. It may be used by the AppStream distro metadata generator to determine the translation status of the respective software (e.g. which languages the software is translated into and how complete the translations are).

The tag must have a type property, assuming the value of the translation system which is used. Right now, allowed translation systems and values for type are:

  • gettext

  • qt

In case a software components gets its translation from multiple translation domains, the <translation/> tag may be defined more than once.

The source strings in the component are assumed to be in the en_US locale. If that is not the case, specify the source locale in POSIX format using the source_locale attribute on the <translation/> tag. The metadata generator will use the source locale to synthesize a <lang/> tag for the source locale, with 100% translation.

For Gettext translations, localization data will be looked for in ${prefix}/share/locale/${locale}/LC_MESSAGES/${id}.mo, where ${id} is replaced with the translation domain specified in the <translation/> tag. For Qt translations, if the ID string contains slashes, we will look for translations following either the ${prefix}/share/${id}_${locale}.qm or the ${prefix}/share/${id}/${locale}.qm pattern. If no slashes are contained, we will look for translation data in ${prefix}/share/locale/${locale}/LC_MESSAGES/${id}.qm.


<translation type="gettext">foobar</translation>
<translation type="gettext" source_locale="de_DE">foobar</translation>
<translation type="qt">FooBar/translations/foobar</translation>

The <suggests/> tag is an optional tag which can be added to specify the component-ids of other software this components suggests. Software centers might present the suggested software on the installation page of the described component.

The tag may have a type property, with the value upstream, indicating that this suggestion originates from the upstream project. If no type property is given, upstream is implicitly assumed as value. Metainfo files must not define other suggests types, those are reserved for AppStream catalog XML (see <suggests/> in catalog XML).

The suggests tag must have one or more <id/> tags as children, specifying the IDs of the suggested other software components.



The <content_rating/> tag is an optional tag which can be added to specify age ratings for the respective software components. These maybe be used for parental control or to display their information in software centers.

The tag must have a type property, indicating the type of the rating system that is used. At the moment, the Open Age Ratings Service (https://hughsie.github.io/oars/) (value oars-1.0) is supported natively, but more services might be added in future.

The <content_rating/> tag may have <content_attribute/> children which each must have an id property indicating the specific section that is rated. Their value indicates the intensity of the rated section and can be one of:

  • none - no rating given

  • mild

  • moderate

  • intense

In case the <content_rating/> tag is empty (no <content_attribute/> is present), it is assumed that the component was checked for age ratings and no age restrictions apply.

The website of the Open Age Ratings Service provides an online form (https://hughsie.github.io/oars/generate.html) which will automatically generate AppStream compatible metadata based on a set of questions answered about the content.


<content_rating type="oars-1.0">
  <content_attribute id="drugs-alcohol">moderate</content_attribute>
  <content_attribute id="language-humor">mild</content_attribute>

The <agreement/> tag is an optional tag which can be added to specify agreements the user has to accept or acknowledge before using the software. This tag can appear multiple times, if multiple agreements are required for a software component.

The tag should have a type property, indicating the type of the agreement. If the type property is missing, an agreement of type generic is assumed. Currently recognized agreement types are:

  • eula - an end-user license agreement the user has to accept before installing the software.

  • privacy - a privacy statement for the software, usually a GDPR (https://www.eugdpr.org/) compliant statement

The <agreement/> tag must have a version_id property, containing a version identifier for the license. It may be used by client applications to determine whether an agreement needs to be shown again after it has been accepted already by the user.

Every <agreement/> must have <agreement_section/> children which each have an id property indicating the specific section that they describe (e.g. introduction). These values may be used to automatically jump to a specific section. Each <agreement_section/> has a translatable name child denoting the name or title of the respective section, and a description child that is translated according to the same translation rules that apply to the <description/> tag. The description contains the content of the respective agreement section.


<agreement type="privacy" version_id="1.0">
    <agreement_section id="introduction">
          We hold personal data about vendors, administrators, clients and other
          individuals for a variety of purposes.

    <agreement_section id="scope">
          This policy applies to all users who have access to any of the personally
          identifiable data.


The <update_contact/> tag is an optional tag which can be added to provide an email address distributors can use to contact the project about invalid or incomplete metadata or – in case the specification has changed – about old metadata. It can also be used to ask general questions in case of an update of the component described in the metadata file.

The <update_contact/> tag must only be used by distributors. It is not included in the distribution-provided AppStream XML file, and therefore not exposed to the end user via any kind of UI.

Upstream authors might decide to add an email address in cleartext, but spam protection using _AT_ is also valid. The value of this tag is generally treated a case-insensitive way.



Variant suffix that software centers may append to the component name on lists in case multiple components have the same name. This is currently primarily used for firmware, where components only need to be distinguished if multiple variants are displayed. A name variant suffix could e.g. be 'Prerelease' or 'China'.


The <branding/> tag is an optional tag which defines properties affecting the branding and presentation of the component. It usually affects how the component is displayed in software centers and on websites.

The tag may currently only contain color tags as children, defining accent colors for the component. Each color element contains an HTML hexadecimal color string as its value. This string must start with a # character. An accent color may for example be used as the background behind the logo/icon of an application.

A color tag must have a type attribute which denotes the color type. The color type may currently only be primary. A color tag may have an optional scheme_preference attribute which denotes a preference for a particular color scheme where this color should be used over other colors. Values for this attribute may either be light or dark for a light or dark theme preference. Each color type/scheme combination may only appear once.


  <color type="primary" scheme_preference="light">#ff00ff</color>
  <color type="primary" scheme_preference="dark">#993d3d</color>

The <tags/> tag is an optional tag which can be used to give the component one or multiple arbitrary labels. For example, it can be used for apps to tag themselves as "featured" in specific software centers, or to group software together by some well-defined criteria.

The interpretation of tags is completely defined by the client application that is reading AppStream metadata. Tags defined in metainfo files may be filtered by catalog metadata generators, and may even be completely ignored by clients. Components must not rely on the presence of specific tags to behave correctly.

The tags tag must have tag children which must have a value comprised only of lower-case ASCII characters, dots, hyphens and numbers. Spaces are not allowed. The tag must also have a namespace attribute to designate a namespace where the particular tag is valid. The namespace is an arbitrary string which has the same character limitations as the tag value. It may for example be the name of the client too that consumes the data, or the name of the organization the tag belongs to.


  <tag namespace="lvfs">vendor-2021q1</tag>
  <tag namespace="plasma">featured</tag>

The <references/> element is an optional tag to indicate references to this component in other registries. This is primarily used for scientific registries, citation information and DOI (Digital Object Identifier (https://en.wikipedia.org/wiki/Digital_object_identifier)) associations.

This information is primarily consumed by specialized tools, but may also be shown by software centers or read by the applications themselves to compose references.

The references element may have doi children containing DOI identifier strings as value, citation_cff children containing a link to a citation file in CFF (Citation File Format (https://citation-file-format.github.io/)) format or registry children. A registry child must have a name property containing the name of a registry referencing this component, while the value of it must be the identification string in the respective registry.


  <registry name="SciCrunch">SCR_000000</registry>

The <custom/> tag is an optional tag which can be used as a key-value store for custom values that are not covered by the AppStream specification. The tag is usually stripped out or filtered by catalog metadata generators, such as appstream-generator. When present, the data contained in a custom can be read by all tools making use of AppStream metadata, making it an ideal extension point when using an existing AppStream library is desired and some custom additions to the metadata are still required. The custom tag is also often used for prototyping new features in AppStream.

The tag must have value children which must have a key property. The value of the value tag denotes a user-defined value, while the key string set for the key property denotes a user-specified key string. The key must be unique; multiple keys with the same name are not allowed.

To avoid name conflicts, it is recommended to prefix keys with a vendor prefix, like GNOME:: or KDE::.


Before using a custom tag, please consider if there is a better way to achieve your goal than adding the data to the AppStream metainfo file, or whether AppStream maybe already contains a way to achieve what you want. Additionally, if you think that the purpose you use the custom tag for is generally useful, please file a feature request against AppStream, so we can discuss adding the new feature to the specification and make it more usable for a bigger audience.


  <value key="MyCorp::app_color">#FF0000</value>
  <value key="MyCorp::special_id">284fd262-6870-42a6-89a4-b189d3109e3e</value>

An example for a very basic component file could look like this:

<?xml version="1.0" encoding="UTF-8"?>
  <name>Foo Bar</name>
  <summary>A foo-ish bar</summary>
  <url type="homepage">https://www.example.org</url>

    <release version="1.2" date="2015-02-16" />
  <developer id="org.example">
    <name>FooBar Team</name>

For a component of type generic, the minimal amount of required tags is: <id/>, <name/>, <summary/>, <metadata_license/>.