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I currently use Firefox 3.6. Before I install the next version of Firefox (Firefox 4 at this time), is there an easy way to check which of all my installed extensions/add-ons are compatible with it?


I am hoping for a one-click solution, since I don't want to install FF4 first and than see some of them incompatible, and I don't want to check every homepage of every installed extension to see which version they support.

Perhaps there exists an 'list highest compatible FF version of each add-on' extension? I googled for this but couldn't find anything...

This question is also kind of generic for any future versions of FF, as I had the same problem when going from FF 1 to 2, and from 2 to 3. Back then, I didn't mind fiddling about and trying various things, now I do.

Edit: Ideally, I should be able to check a checkbox somewhere to make an extension (or Firefox itself --> hint for the FF developpers) monitor whether my add-ons are compatible, and notify me (with a pop-up) once they are, so I can upgrade. While I guess it's nice for statistics and so that Mozilla provides a huge list of compatible extensions and the average user adaoption, it would have been more useful if I as a user could more easily check my personal situation.

Edit 2: Seems I was not alone with my question: see this lifehacker post.

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It not just ansver. But it may be useful. If extension, without I cant live, incompatible with fresh release of firefox, I fix compatiblity in install.rdf and its work. Extension really is a zip. Some extensions update very slow. – mmv-ru Apr 4 '11 at 14:15
The technical answer is that you check the APIs that the extension uses against the API/ABIs changed in each new version. Pretty hard, no idea how. – tobylane Apr 11 '11 at 19:18
up vote 10 down vote accepted

Maybe the Firefox add-on Is it compatible? will help you (it helped me). It simply adds compatibility information into the list of installed add-ons.

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Seems to be exactly what the OP was searching for. I've installed it myself. – Al E. Apr 6 '11 at 13:20
Yeps, indeed, this is what I was looking for. I see the answer date is April 4. It seems I didn't notice your answer then (and started a bounty without good reason). Stupid me ! – Rabarberski Apr 12 '11 at 6:25
I think you also missed out on the Add-on Compatibility Reporter, a better and more comprehensive solution. See my answer. – harrymc Apr 14 '11 at 6:12
@harrymc: I didn't miss the add-on compatibility reporter. It is targeted however to alpha and beta users, so I didn't consider it (even after reading the description) – Rabarberski Apr 26 '11 at 9:39
@Rabarberski: It works very well for all users. And while testing the compatibility of an add-on, you are a beta-tester. – harrymc Apr 26 '11 at 11:25

Or perhaps you could check out the Add-on Compatibility Center.

There is a report there that lists the add-ons that make up 95% of all installed add-ons sorted by popularity. (I'd link it but there's no direct URL.)

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Indeed this is what your looking for Click on View Compatibility Report then View Detailed Report. – Jeff F. Apr 4 '11 at 13:21
This does require me check each add-on against the list. Still too much work, sorry... – Rabarberski Apr 4 '11 at 13:50

First a remark: I suggest in any case to wait for FF 4.1, because version 4.0 is quite unstable. It was aborting frequently, so finally I just went back to FF3. I believe that the new Javascript engine still has problems.

Now to address your question : There is no sure way to know if an add-on is compatible with FF4. Even if it is marked as incompatible and disabled by FF4, it may still in actual fact be perfectly compatible. You just have to try and see, and the simplest way is to turn off the check.

To Force Firefox Extension Compatibility, version check is turned off in about:config : Right-click on the list and choose ‘New’ (see first if it is already there), followed by ‘Boolean’. Enter the name as ‘extensions.checkCompatibility’ and the value as ‘false’. Once done, extensions will no longer check to see if they are compatible with the version of Firefox you are running. You can re-enable the check again at any time by setting it to ‘true’.

A much better way of doing this, while at the same time helping the community, is presented in this article : Test and Report Add-on Compatibility in Firefox.

One installs the Add-on Compatibility Reporter, which enables all your incompatible extensions for you to test whether they still work. If you notice that one of your add-ons doesn't seem to be working the same way it did in previous versions of the application, just open the Add-ons Manager and click Compatibility next to that add-on to send a report to Mozilla. You can of course also report that an extension is working perfectly well.

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You could try using Firefox Portable Edition. That way you could check out Firefox 4 and its compatibility with your add-ons without uninstalling your current version of Firefox.

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Hmm, that would require me to look which extensions I have installed, and install each one of them in the portable version. Too much trouble. – Rabarberski Apr 4 '11 at 13:31

This is not a one-click solution but in my opinion it's the most flexible: I would install Firefox 4 in a different directory than Firefox 3, then make a copy of the profile. You will use Firefox 3 with your old profile and Firefox 4 with the new one. Firefox 4 will check add-on compatibility as soon as it's started.


  • Firefox 4 itself will check compatibility
  • You can go back to Firefox 3 whenever you want
  • Can wait until all the extensions catch up or Firefox 4 gets to a point where you're satisfied with it, then effortlessly switch to the new version.


  • Not a one-click solution
  • Increased disk footprint (but usually not an issue unless the system is very tight on space, e.g. netbook with small SSD)

To make a copy of the profile, just start Firefox 3 with the profile manager enabled (if you don't know how see the Mozilla site), then create a new profile. Exit, open the folder where profiles are stored (this depends on the OS you're using and the specific version) and copy the old profile over the new one.

The operation can be done in about 10-15 minutes if you've never done it before.

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Try the " is it compatible " add on I haven't tried it but this might be what you are looking for.

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Indeed, this is what I was looking for ! – Rabarberski Apr 12 '11 at 6:23
Errr...that's what Martin suggested in his answer. – Al E. Oct 7 '11 at 19:29

Like @Rabarberski I find the Add-on Compatibility Report for Firefox <release> not usable to keep my workflow sane. As for Is It Compatible? it was not validated and ceased to work since FF v30.

My temporaty solution atm: I backup (snapshots) the whole profiles and keep the previous Firefox package. This allows me to blindly update (Mozilla way), and downgrade to the previous release in case of trouble with limited hassle. Firefox Portable is not available on Linux.

Also, here is a question asking for more information on this subject on Mozilla support

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As much as you seem to not want to, the easy answer is to install Firefox 4. If something doesn't work, just reinstall 3.x back over it. Your extensions/settings/etc will be preserved.

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So, I should just do this every week or so, until all extensions are compatible? That's exactly the reason why I specified that I don't want to try by installing FF4 and see what happens. – Rabarberski Apr 4 '11 at 13:11
Are your extensions actually incompatible, or are you just pulling your hair out from worry because it maybe could happen? – Hyppy Apr 4 '11 at 13:24
thanks for the feedback. I had incompatible extensions across every major FF version upgrade, so I expect the same to happen now. I am looking for a solution that I can reuse in the future as well. – Rabarberski Apr 4 '11 at 13:30

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