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Geoff Lankow edited this page Aug 17, 2015 · 13 revisions

How automatic browser detection works

Windows

Open With looks for entries in the Windows registry, under the key HKEY_KEY_LOCAL_MACHINE\Software\Clients\StartMenuInternet. It also looks for the presence of Microsoft Edge (Windows 10) in C:\Windows\SystemApps\Microsoft.MicrosoftEdge_8wekyb3d8bbwe (or if C:\Windows isn't your Windows directory, the corresponding place in your Windows directory).

OS X

Open With looks for .app files in your local applications directory. The browsers it looks for are: Camino, Google Chrome, Chromium, Firefox, Flock, Opera, Safari, and SeaMonkey.

Linux (and others)

Open With looks for google-chrome.desktop, chromium-browser.desktop, firefox.desktop, opera.desktop, and seamonkey.desktop in these locations: ~/.local/share/applications, /usr/local/share/applications/, and /usr/share/applications/.

How to override automatic settings using about:config

(You can change almost all of these using the Open With options tab. Do that instead.) Firstly, some context. Each browser entry has a "key name" used for settings in about:config. For auto-detected browsers, the key name is auto. followed by the name of the file detected (firefox.exe in Windows, firefox in OS X, firefox.desktop in Linux). Edge is a special flower and has the key name auto.msedge. Manually added entries have a 8-character generated key name prefixed by manual., for example manual.zvsOKR6Y. You'll see the manual entries in about:config already. Some manual entries might not have a generated key name if you had an older version of Open With.

To set extra properties on a browser entry, add pref entries named extensions.openwith.{key name}.{pref}. Valid prefs are:

  • icon (string) The icon for the entry as a URL, usually a file:// URL.
  • keyinfo (string) The keyboard shortcut. Open With is fussy about the format. Use the options tab instead.
  • name (string) Name to display for the entry.
  • hidden (boolean, for automatic entries only) Whether this entry is hidden, obviously.
  • usefilepath (boolean, for manual entries only) If the URL to be opened is a file:// URL, pass the path to the file instead of a URL. Only really useful if you're trying to do something quite unusual.