How can I configure a domain-specific default browser?

If the url matches .*\.myemployer\.com.* then I want the link to open in chromium. Otherwise I want it to open in brave. Is this possible? If so, how?

Note that there is a difference between the text/html mimetype (this is opening actual HTML files) and the x-scheme-handler/http mimetype (this is an HTTP URL). I assume you want to customize how external applications open HTTP/HTTPS URLs, since you mention domains. (Note that this is for external applications. Customizing how a particular browser handles an HTTP URL is a different thing altogether.)

One tricky thing about custom URL handlers is that there are at least four files the associations might be stored in, depending on the application / library the application uses:

• ~/.config/mimeapps.list (the right place to make changes)
• ~/.local/share/application/mimeapps.list (the deprecated location)
• ~/.local/share/application/defaults.list (the older deprecated location)
• ~/.local/share/applications/mimeinfo.cache (the cache)

I've been doing some work on custom URL handlers lately, so I've adapted some of that for this purpose. Here are the instructions:

1. Check the currently registered file for the protocols. Here's what they look like for me:

   $ gio mime x-scheme-handler/http
   Default application for “x-scheme-handler/http”: firefox.desktop
   Registered applications:
           firefox.desktop
           chromium-browser.desktop
   Recommended applications:
           firefox.desktop
           chromium-browser.desktop
   $ gio mime x-scheme-handler/https
   Default application for “x-scheme-handler/https”: firefox.desktop
   Registered applications:
           firefox.desktop
           chromium-browser.desktop
   Recommended applications:
           firefox.desktop
           chromium-browser.desktop
   

2. Write a script that parses the URL and launches the appropriate browser.

   I prefer to use Python, since it has libraries to parse URLs and send errors to syslog.

   #! /usr/bin/env python3
   
   import subprocess
   import logging
   import argparse
   import syslog
   import sys
   
   try :
       from urllib.parse import urlparse
   except ImportError:
       from urlparse import urlparse
   import os.path
   
   def http_url(url):
       if url.startswith('http://'):
           return url
       if url.startswith('https://'):
           return url
       else:
           syslog.syslog(syslog.LOG_ERR, sys.argv[0] + ": not an HTTP/HTTPS URL: '{}'".format(url))
           raise argparse.ArgumentTypeError(
               "not an HTTP/HTTPS URL: '{}'".format(url))
   
   if __name__ == '__main__':
       parser = argparse.ArgumentParser(
           description='Handler for http/https URLs.'
       )
       parser.add_argument(
           '-v',
           '--verbose',
           help='More verbose logging',
           dest="loglevel",
           default=logging.WARNING,
           action="store_const",
           const=logging.INFO,
       )
       parser.add_argument(
           '-d',
           '--debug',
           help='Enable debugging logs',
           action="store_const",
           dest="loglevel",
           const=logging.DEBUG,
       )
       parser.add_argument(
           'url',
           type=http_url,
           help="URL starting with 'http://' or 'https://'",
       )
       args = parser.parse_args()
       logging.basicConfig(level=args.loglevel)
       logging.debug("args.url = '{}'".format(args.url))
       parsed = urlparse(args.url)
       if parsed.hostname == 'askubuntu.com':
           browser = 'firefox'
       else:
           browser = 'chromium-browser'
       logging.info("browser = '{}'".format(browser))
       cmd = [browser, args.url]
       try :
           status = subprocess.check_call(cmd)
       except subprocess.CalledProcessError:
           syslog.syslog(syslog.LOG_ERR, sys.argv[0] + "could not open URL with browser '{}': {}".format(browser, args.url))
           raise
   

   Adapt the script to your liking, particularly the executable for brave (I haven't used it, so I don't know) and the hostname in the if parsed.hostname part.

3. Test the script from the current directory.

   This should open with Firefox:

   $ ./http_url_handler.py 'https://askubuntu.com/questions/1161752/how-can-i-configure-a-domain-specific-default-browser'
   

   This should open with Chromium:

   $ ./http_url_handler.py 'https://superuser.com/questions/688063/is-there-a-way-to-redirect-certain-urls-to-specific-web-browsers-in-linux/'
   

4. Add the script to your $PATH so the desktop file can find it.

   I use a bin directory like this:

   $ mkdir ~/bin/
   

   and add this to ~/.profile (note you will need to log out and log in again to see changes):

   PATH="$HOME/bin:$PATH"
   

   and finally either copy or symlink the script to ~/bin:

   $ ln -s $PWD/http_url_handler.py ~/bin/
   

   If you did this properly, you should see this:

   $ type -a http_url_handler.py 
   http_url_handler.py is /home/nathaniel/bin/http_url_handler.py
   

   not this:

   $ type -a http_url_handler.py 
   bash: type: http_url_handler.py: not found
   

5. Test the script from your home directory.

   This should open in Chromium:

   $ http_url_handler.py 'https://superuser.com/questions/688063/is-there-a-way-to-redirect-certain-urls-to-specific-web-browsers-in-linux'
   

   This should open in Firefox:

   $ http_url_handler.py 'https://askubuntu.com/questions/1161752/how-can-i-configure-a-domain-specific-default-browser'
   

6. Install the desktop file. Here's the one I used:

   [Desktop Entry]
   Name=HTTP URL handler
   Comment=Open an HTTP/HTTPS URL with a particular browser
   TryExec=http_url_handler.py
   Exec=http_url_handler.py %u
   X-MultipleArgs=false
   Type=Application
   Terminal=false
   NoDisplay=true
   MimeType=x-scheme-handler/http;x-scheme-handler/https
   

   Either via desktop-file-install:

   $ desktop-file-install --dir=$HOME/.local/share/applications/ http-url-handler.desktop
   

   or manually copy the http-url-handler.desktop file to the proper directory, which should be ~/.local/share/applications/:

   $ cp http-url-handler.desktop ~/.local/share/applications/
   

   These are the most important lines in the desktop file:

   Exec=http_url_handler.py %u
   MimeType=x-scheme-handler/http;x-scheme-handler/https
   

7. Make the desktop file executable.

   $ chmod +x $HOME/.local/share/applications/http-url-handler.desktop
   

   This is necessary because of a security precaution.

8. Register the desktop file with the x-scheme-handler/http and x-scheme-handler/https mimetypes.

   $ gio mime x-scheme-handler/http  http-url-handler.desktop
   Set http-url-handler.desktop as the default for x-scheme-handler/http
   $ gio mime x-scheme-handler/https http-url-handler.desktop
   Set http-url-handler.desktop as the default for x-scheme-handler/https
   

   All this really does is change lines in ~/.config/mimeapps.list under the [Default Applications] group so that instead of this:

   x-scheme-handler/http=firefox.desktop
   x-scheme-handler/https=firefox.desktop
   

   it says this:

   x-scheme-handler/http=http-url-handler.desktop
   x-scheme-handler/https=http-url-handler.desktop
   

   You can also add it under the [Added Associations] group with a text editor so it looks something like this:

   x-scheme-handler/http=http-url-handler.desktop;firefox.desktop;chromium-browser.desktop
   x-scheme-handler/https=http-url-handler.desktop;firefox.desktop;chromium-browser.desktop
   

   Some older applications use ~/.local/share/application/mimeapps.list, but this is officially deprecated. However, the xdg-mime command uses this location anyway:

   $ xdg-mime default http-url-handler.desktop x-scheme-handler/http
   $ xdg-mime default http-url-handler.desktop x-scheme-handler/https
   

   There is also an even older deprecated file called defaults.list that is still used by some applications. Edit this file with a text editor:

   $ edit ~/.local/share/applications/defaults.list
   

   and manually add these lines:

   x-scheme-handler/http=http-url-handler.desktop
   x-scheme-handler/https=http-url-handler.desktop
   

   under the [Default Applications] group.

9. Check if it was successfully registered.

   $ gio mime x-scheme-handler/http
   Default application for “x-scheme-handler/http”: http-url-handler.desktop
   Registered applications:
           firefox.desktop
           chromium-browser.desktop
   Recommended applications:
           firefox.desktop
           chromium-browser.desktop
   $ gio mime x-scheme-handler/https
   Default application for “x-scheme-handler/https”: http-url-handler.desktop
   Registered applications:
           firefox.desktop
           chromium-browser.desktop
   Recommended applications:
           firefox.desktop
           chromium-browser.desktop
   

   If you also added to the [Added Associations] group, it will look like something like this:

   $ gio mime x-scheme-handler/http
   Default application for “x-scheme-handler/http”: http-url-handler.desktop
   Registered applications:
           http-url-handler.desktop
           firefox.desktop
           chromium-browser.desktop
   Recommended applications:
           http-url-handler.desktop
           firefox.desktop
           chromium-browser.desktop
   $ gio mime x-scheme-handler/https
   Default application for “x-scheme-handler/https”: http-url-handler.desktop
   Registered applications:
           http-url-handler.desktop
           firefox.desktop
           chromium-browser.desktop
   Recommended applications:
           http-url-handler.desktop
           firefox.desktop
           chromium-browser.desktop
   

   Check xdg-mime also.

   $ xdg-mime query default x-scheme-handler/http
   http-url-handler.desktop
   $ xdg-mime query default x-scheme-handler/https
   http-url-handler.desktop
   

10. Test some URLs.

    This should open in Chromium:

    $ gio open 'https://superuser.com/questions/688063/is-there-a-way-to-redirect-certain-urls-to-specific-web-browsers-in-linux'
    

    This should open in Firefox:

    $ gio open 'https://askubuntu.com/questions/1161752/how-can-i-configure-a-domain-specific-default-browser'
    

    Now test the same URLs with xdg-open:

    $ xdg-open 'https://superuser.com/questions/688063/is-there-a-way-to-redirect-certain-urls-to-specific-web-browsers-in-linux/'
    
    $ xdg-open 'https://askubuntu.com/questions/1161752/how-can-i-configure-a-domain-specific-default-browser'
    

11. Update the mimeinfo cache.

    Some applications read ~/.local/share/applications/mimeinfo.cache instead of ~/.config/mimeapps.list. So update the cache:

    $ update-desktop-database ~/.local/share/applications/
    

For convenience, the files are on Github here:

https://github.com/nbeaver/askubuntu-custom-http-url-handler

What you want is very easy, you are just approaching it from the wrong angle.

Create a script (just change mozilla and chrome to full paths of google-chrome and brave.

#!/bin/bash
# Reading argument values using loop
isFound=0;
for argval in "$@"
do
  #echo -n "$argval  "
  if [[ $argval == *myemployer* ]]; then
    isFound=1;
    break;
  fi
done


if [[ isFound -eq 1 ]]; then
    mozilla $@;
else
    chrome $@;
fi

and save this shell script (with the changes as selectBrowser.sh

Next, in this shell script as the default browser.

Done.

After a bit of poking around, I think the component I'm looking for is part of Gnome. There appears to be a correspondence between mime types and apps:

❯ gio mime text/html
Default application for “text/html”: chromium-browser.desktop
Registered applications:
    firefox.desktop
    chromium-browser.desktop
    brave-browser.desktop
    vim.desktop
    nvim.desktop
    org.gnome.gedit.desktop
Recommended applications:
    firefox.desktop
    chromium-browser.desktop
    brave-browser.desktop

There's also some info here: https://help.gnome.org/admin/system-admin-guide/stable/mime-types-application.html.en

Following a good idea from @RobertRiedl, I may register a "browser" on the text/html mimetype which is actually just a small program that will check the string and then launch the desired program. I figure you could use this to drive other mimetype remappings too.

If I get this working I'll update this answer with details.