It took some jumping through hoops (including a mailing list subscription that I apparently didn't need) but I finally found where to download the Firefox ESR. This is great for fresh installs, but I was wondering if there's a way to simply convert existing installations to the ESR configuration without having to do a full install.

As I understand it, the only difference between ESR and regular Firefox will be how they receive updates. After the new standard version of Firefox comes out, ESR releases will only receive critical security updates and bug fixes for the remainder of their support life. Newer versions of Firefox's standard build will have all the latest and greatest features, while ESR releases are meant to provide stability for environments that can't be expected to keep up with a new full version number change as often as Mozilla does them.

In regular Firefox, the About screen shows that I am using the "release" update channel.

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Is switching to ESR really just a matter of switching the update channel? I presume this can be done in about:config by changing app.update.channel and probably also app.update.url. However, I don't know what these values should be for ESR or if anything else should be tweaked.

So, is it possible to switch to ESR without a reinstall and, if so, how?

(Note: While this question was written originally for Firefox 10, I expect any answers will apply to future ESR versions as well.)

  • Have you tried to install the ESR to see if your theory is correct? – Ramhound Mar 5 '12 at 18:45
  • @Ramhound Power's out at my house now, so I don't currently have access to the VMs on my laptop to test it. Also, I wouldn't know where to begin looking for other changes I'm not expecting. – Iszi Mar 5 '12 at 18:56
  • To clarify your understanding of the differences between a normal and ESR release, ESR releases don't get feature updates, and bugs are generally going to be treated as features unless they are of a security, "topcrash" or dataloss nature. Users on ESR releases also are excluded from the normal support channels, and are expected to use the enterprise mailing list for support. – Stephanie Jun 15 '12 at 4:22
  • Also with respect to ESR, when you do eventually have to upgrade, expect more changes thrown on you at once, rather than the gradual change that the rapid release process gives. – Stephanie Jun 15 '12 at 4:27

Converting to ESR is done in principle by updating in defaults\pref\channel-prefs.js this line :

pref("app.update.channel", "esr");

According to the mozillaZine thread Changing Your Update Channel, it's hard coded in the channel-prefs.js file, so changing in about:config will not work.

However, not every non-ESR version can be converted to ESR just by changing channel-prefs.js. The ESR version is entirely distinct from the normal version, even if the differences are very minimal for a given version, so one should use the released ESR version. Even if updating channel-prefs.js works for the some version such as Firefox 10.0, there is no guarantee that this will work for the next ESR version.

This is clearly shown in the article Enterprise/Firefox/ExtendedSupport :


You can see from the above image that not every Firefox version has a corresponding ESR version. There are much fewer ESR versions than "normal" ones. The article also says that testing if a new ESR version fits the needs of your organization is your responsibility.

Because of all these differences, I would advice against converting an existing Firefox installation to ESR, but would rather start from a clean ESR installation.


ESR Builds are built separately from normal builds, even of the same version. Firefox 10.0 and Firefox ESR 10.0 and separate bundles, albeit largely identical. You may be able to drop in ESR's app.update.* config to cause the next ESR update to overwrite your installation, but this is not tested or supported as far as I'm aware.

The easiest way to go about replacing an install would probably be to run the ESR installer, but select your existing install folder. This should in-place replace your install without blowing away your profile/etc., though may not pass your criteria of 'without reinstall'.


You can try to install ESR (I don't really think this is re-install, more of an upgrade using the installer) on top of the current Firefox installation. This way the profile is preserved and no data will be lost.

Note: I have upgraded Firefox, downgraded Firefox, and switch around update channels with this method and I didn't lose a tab opened.


As far as I am aware, there is no current way to simply hop across to another channel without an install. However, all of your data (cookies, history, extensions, preferences, etc.) is stored in a profile. As long as you keep this profile, your settings will be untouched.

I believe that profiles are preserved (or you have the option to preserve profiles) when you uninstall Firefox, but to be on the safe side, just backup your current profile. The location of your profile(s) can be found by going to C:\Users\**<your username>**\AppData\Roaming\Mozilla\Firefox\Profiles. Just make sure that you backup this before installing Firefox ESR.

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