Freedesktop quick reference

In order to ensure interoperability, flatpak adheres strictly to a number of freedesktop standards and practices. This page describes the basic conventions that should be followed when building a flatpak app.

Icons

Application icons can be in either png or svg format, must use the application’s appid as a prefix and be placed in /app/share/icons/hicolor/$size/apps/

Example:

/app/share/icons/hicolor/128x128/apps/org.gnome.Dictionary.png

If interested, you can read the full spec here

Desktop files

Desktop files are used by desktop environments in order to identify and display available applications to the user, they contain information about how to launch the application, its icon and categories among others.

A minimal desktop file needs at least the application’s Name, Exec command, Type and Icon:

[Desktop Entry]
Name=Gnome Dictionary
Exec=org.gnome.Dictionary
Type=Application
Icon=org.gnome.Dictionary

Your desktop file should be prefixed with your application’s appid and placed in /app/share/applications/, you should use desktop-file-validate to check your file for errors before including it.

Example:

/app/share/applications/org.gnome.Dictionary.desktop

You can find more information here. If interested, you can read also the full spec here.

Appdata files

Appdata files are used by application stores (eg. kde discover, gnome software) in order to display metadata about your application, such as a description, screenshots, display changelogs on update, among other things.

your desktop file should be prefixed with your application’s appid and placed in /app/share/metainfo/, you should also use appstream-util validate-relax to check your file for errors before including it.

Example:

/app/share/metainfo/org.gnome.Dictionary.appdata.xml

If interested, you can read the full spec here