View source for xdg-open/how to/add custom protocol

{{fmt/title|How to add a custom protocol}}
The following instructions were adapted from ChatGPT<ref name=chatgpt1 /> but tested and modified slightly for clarity.
==Create a custom desktop file==
Create a new desktop file for your custom protocol. Desktop files usually have a <code>.desktop</code> extension and are located in the <code>/usr/share/applications/</code> directory or <code>~/.local/share/applications/</code> for user-specific settings.</p><p>Example (<code>custom-protocol.desktop</code>):</p>
 [Desktop Entry]
 Name=Custom Protocol Handler
 Exec=/path/to/your/custom-protocol-handler %U
 Terminal=false
 Type=Application
 MimeType=x-scheme-handler/{{arg|protocol name}};
That is: if your custom protocol is (e.g.) "wooz://{{arg|URI}}", then '''MimeType''' should be set to <code>x-scheme-handler/wooz</code>.

Customize the <code>Exec</code> line to point to the executable that will handle your custom protocol.
==Update MIME types==
Open the file <code>/usr/share/applications/mimeinfo.cache</code> or <code>~/.local/share/applications/mimeinfo.cache</code> and add the following line:
 x-scheme-handler/{{arg|protocol name}}=custom-protocol.desktop;

If the <code>mimeinfo.cache</code> file doesn't exist, you may need to create it.
==Update the MIME database==
Run the following command to update the MIME database:
<syntaxhighlight lang=bash>
update-desktop-database ~/.local/share/applications/
</syntaxhighlight>
If you added the desktop file to the system-wide directory (<code>/usr/share/applications/</code>), you might need to run the command with superuser privileges:
<syntaxhighlight lang=bash>
sudo update-desktop-database /usr/share/applications/
</syntaxhighlight>
==Test your custom protocol==
After completing the above steps, you should be able to use <code>xdg-open</code> with your custom protocol. For example:
 xdg-open {{arg|protocol name}}://example

This should launch the specified handler for your custom protocol.</p></li></ol><p>Remember to replace "custom-protocol" with your actual protocol name and update file paths accordingly. Additionally, depending on your desktop environment, there may be slight variations in the steps. If your desktop environment supports <code>xdg-open</code>, these general steps should work.
==Footnotes==
<references>
<ref name=chatgpt1>'''2024-01-01''' ChatGPT 3.5, in response to "How can I add a custom protocol to xdg-open?"</ref>
</references>