How to Change Default Applications in Ubuntu for Web, Email, and Media

When you set up a fresh installation of Ubuntu, the operating system assigns default software packages to handle core daily tasks: Mozilla Firefox for web browsing, Thunderbird for email correspondence, Rhythmbox for music, and GNOME Videos (Totem) for video playback. However, many desktop users immediately install their own preferred tools—such as Google Chrome, Brave, VLC Media Player, Spotify, or Visual Studio Code.

Clicking an HTML link in a document or double-clicking an MP4 video clip only to have it launch inside the wrong application creates friction throughout your workday. Fortunately, Ubuntu includes a centralized, graphical control panel where you can define global default applications, alongside file-level association managers for custom file formats. This guide explains how to set your preferred default applications in Ubuntu.

Setting Core Default Applications in Ubuntu Settings

Configuring system-wide defaults for standard categories takes under a minute:

1. Click the System Menu in the top-right corner of your desktop panel (the volume and network cluster) and click the Settings gear icon.
2. In the left-hand navigation sidebar, scroll down and click on Default Applications (or Apps > Default Apps on newer Ubuntu releases).
3. You will see primary category dropdown selectors:
   • Web: Select your preferred browser (e.g. Google Chrome, Firefox, or Brave).
   • Mail: Choose your default desktop email client (e.g. Thunderbird).
   • Calendar: Assign your calendar manager.
   • Music: Choose your audio player (e.g. VLC Media Player or Audacious).
   • Video: Select your primary media player (e.g. VLC).
   • Photos: Select your image viewer (e.g. Image Viewer (eog) or gThumb).
4. Click any dropdown menu and choose your installed application. The change applies instantly without requiring a system reboot.

Changing File-Type Associations for Specific Formats (e.g. PDF, MP4, MKV)

If you want specific file extensions (like PDF documents or MKV video files) to always open in a specialized viewer:

1. Open the Files (Nautilus) file manager.
2. Locate any file with the target extension (for example, a .pdf or .mkv file).
3. Right-click the file and choose Properties from the context menu.
4. In the properties dialogue box, click on the Open With tab.
5. Scroll through the list of recommended and installed applications to find your preferred tool (such as Document Viewer or VLC).
6. Click on the application name to highlight it, then click the Set as default button in the bottom-right corner.
7. Close the Properties dialogue.

From now on, double-clicking any file with that extension will reliably launch your chosen program.

Managing Default Applications via Terminal (xdg-mime)

For system administrators configuring multiple Ubuntu workstations or setting defaults via bash scripts, the FreeDesktop xdg-mime command provides full control:

1. Open the Terminal (Ctrl + Alt + T).
2. To set Google Chrome as your default web browser:

   xdg-settings set default-web-browser google-chrome.desktop

3. To set VLC as the default handler for MP4 video files:

   xdg-mime default vlc.desktop video/mp4

4. To query the current default application for a file type:

   xdg-mime query default video/mp4