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You know about those frustation we’ve always have whenever Firefox enter its major software update: hoping that the new Firefox will still support our lovely plugins from the old Firefox. Sadly, that’s not always the case. And the kind plugin developer who already devoted his time for the plugin that maybe so simple and not interested in changing internal version in the plugins to be verified “compatible” with the new release of Firefox. So I’ll give you a tips that in fact has already been circulated among some advanced Firefox users to workaround the plugins compatibility issues.
This trick is known to work up to Firefox 4, and will be expected to work in the future release of Firefox. But at least we hoping that Firefox will turn off this compatibility issues so that we will stop doing the same dance over and over again every time a new major Firefox release is out.
Update: I’ve made small updates to accommodate Firefox 5 Final that’s already coming few days ago. Thanks to Kenneth Thomas that remind me of the version difference.
Tips: It seems that installing Add-on Compatibility Reporter will also enables you to install (or run) incompatible extensions to Firefox as well.
Update: Since Firefox 10, the Add-on Compatibility Reporter just works as a reporter tool, and cannot be used as a tool to force install incompatible extension, because Firefox 10 and later has a new policy that allows all the add-on that opt-in to “Compatible by Default” to run. For more information, refer to this article.
1. Open the Firefox browser.
2. Write about:config in the awesome bar (aka address bar). Click “I’ll be careful, I promise!” button. This will open a list about Firefox not-so-secret configuration.
3. Right-click anywhere. Choose New > Boolean.
4. Enter extensions.checkCompatibility into the next window and click OK.
Update: Because of the rapid development of Firefox version, it seems that you have to change a bit of the code to accommodate the changes. Just use
extensions.checkCompatibility.5.0 instead for Firefox 5,
extensions.checkCompatibility.6.0 for Firefox 6,
extensions.checkCompatibility.7.0 for Firefox 7,
and so on. I’ll check occasionally by myself whether those tricks still working or not for future release of Firefox.
5. Select false value at the next window and click OK.
6. Once again, right click at anywhere, select New > Boolean, and click OK.
7. Enter extensions.checkUpdateSecurity into the next window and click OK.
8. Select false value at the next window and click OK.
9. You’re done! Now if you enter “extensions.check” at the filter bar, it should shows something like this:
10. If it is, then you’re done! You can begin enabling your disabled add on, restart your Firefox, and voila! Your favorite extension is back!
Warning: This could lead to some extension bug and security risk. So use at your own risk.
Life in a Nutshell 
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This will not work for FF 4 and forward, right? 🙂
Why not just link to the Mozilla page with correct instructions 🙂 ?
umm, in fact, from my experience, it is working. I’ve done it for firefox 3.x and 4.x and it’s working. for firefox 4.x, after I applied the instruction, it’s showing notification at the add-on tab, that the addon compatibility check is disabled. btw, if you know the link to the mozilla page, then sharing it would be helpful. 🙂
http://kb.mozillazine.org/Extensions.checkCompatibility
You must use version after 3.6.
thanks for the information. I will follow it up after i got back. 🙂
Great but I found mistype in point 4
extension.checkCompatibility.5.0 have to be extensions.checkCompatibility.5.0
oh okay, thanks for the notification. I will fix it immediately. 🙂
As of a few days ago, it’s 6.0 over here 🙂
Yeah haha I’ve known it, but still have no time to update the post. Thanks for bringing up the matter. 🙂
Thanks.
you’re welcome. 🙂
for more information you can go through the below links:
http://forums.techarena.in/networking-security/1428526.htm#post5407732
Works on 7.01, I added extensions.checkCompatibility as well as extensions.checkCompatibility.7.0 to be on the safe side
Well, I guess with the rapid succession of Firefox’ development version, trial and error is highly needed to perform this solution as Mozilla might changed their code at any time. As far as I know, extensions.checkCompatibility.7.0 alone is already worked for me, but thanks your information. 🙂
doesnt work for me in firefox 8! sad day.
I’m so sorry to hear that. Maybe mozilla has changed the way to bypass the compatibility check. I’ll let you know as soon as I found the solution. Thanks!
I am using Firefox 8.0.1 and it works.
extensions.checkCompatibility.8.0 set to false.
Thanks for the info. The problem is it’s not works on everyone. Or maybe some person forget to change the code into “8.0”.
Works a treat on Firefox 9.0 – saved my life. Thanks so much
You’re welcome. 🙂 I’m now using Firefox from the aurora channel (10.02a) as my main Firefox browser, and it still works. Hope they still allows for incompatibility hacks like this in the future (or just turn off the incompatibility disable check, Mozilla!) 😦
>turn off the incompatibility disable check, Mozilla
You realize it’s there for a purpose, right?
I know I should emphasize on “disable” word at my previous statement. It’s not “incompatibility check”, but “incompatibility disable check”.
That means, I suggest that Firefox may check for incompatibilities, but should not force to disable it if there are incompatibilities. The option to disable or enable must be at the hand of the user. Firefox should just report that an extension is compatible or incompatible, along with options on its right to disable.
In the end, why bother to build a system that force disable incompatible extension, if they put a “secret way” to turn off that filter? It must be meant that any incompatible-reported extension is not always incompatible (maybe just minor obsolete code or version compatibility tag), but they didn’t dare to take any risk putting the decision whether to disable or enable, at the hand of the user. That’s what I meant. If they so sure that any incompatible-reported extension is really that dangerous, they won’t even put any sneak passage to make exception method like described above.
Martin,
I’m with you. FF should have a much easier user experience for this, with relatively easy selection of options, instead of the current obsure setting. 🙂
Sure. 🙂 I wish they make it like Chrome. You almost never heard Chrome’s extension incompatibility problem, despite the Chrome’s auto update, right? That’s why almost no one complained about the Chrome’s auto update policy. 😀
Does not work with Firefox 10.0.2.
I’m fucking tired of those developers who think they know better than me what I should do with my browser. I switched to Midori on my Debian box. It crashes occasionaly on some website mainly because of WebKitGtk, but I can tolerate this slight inconvenience more than those firefox devs zealots!
Yeah. Currently, my main browser is Chrome (which is also a webkit), and my Firefox is in Aurora channel, installed with just minimal essential plugins, to avoid unnecessary “inconvenience”. I seems had (forced) to forget about my old plugins, eventually. 😦 Why can’t Firefox be as transparent as Chrome?
I’m sorry to hear that the above solution doesn’t work for you. I’ll look around for more information, because it (still) works for my Aurora. If I found other solution, I’ll update this page. Thanks.
Doesn’t work my fanny. Works fine with every version of FF (I’ve gone through them all). You’re not doing it right.
Otherwise, you get a free piece of software, provided to you free, and you complain in the language above when the people who wrote it and provided it to you for FREE do what they think is best for most users?
Tell ya what. Grab the source and compile your own version that does what you want, or shut up 🙂
Fair enough. 😀 Well, that’s what they will got when they said they want “user feedback” to “help them improve the browser”. If they don’t want to hear critics, they should have said so. 🙂
This is awesome. Thanks for the post. Quick question. Do you think the compatability check be disabled for all users? Such as in a domain environment? We use redirected profiles and I wonder if I set this as a local administrator if it will be referenced by all accounts or if this is on a per user basis.
Sorry for the late reply. I think if you set the Firefox to work for all users (shared settings), then one setting changed by an Administrator or one user will reflect on another users as well. But Firefox’s default setting is to differentiate between one user’s to another user’s setting, as browsing is a personal experience, not a collective one. But if you’re using centralized profiles (e.g. domain environment) in one server, I think you can change the “default new user” profile so that whenever you create a new user, all the settings, including the “do not check for compatibility” one, will be propagated to the new user profile. I only have a shallow understanding about domain environment and centralized profiles, so I cannot go into further detail, but I hope it gives you proper options for your situation.
I’m using windows 7 running FF 14.0.1 and this didn’t work for me. I followed the instructions changed the value to false but when I restarted the browser the add-on compatibility check ran.
Didn’t work with FF12.0. Plugin check started a few hours ago and I’ve tried every tip that could be found but couldn’t get rid of it.
Update:
Manually removing a bunch of unused plugin .dll files listed in about:plugins solved the problem. After removing the unused .dlls, it’s good to delete pluginreg.dat so it can be recreated with the updated data.
But the problem is you still can’t use the plugin. But thanks for the information. 🙂
I’m using windows 7. When i start FF its not opening, showing only “checking compatibility of Add-ons. It is running more than 1hr. But FF not opnens, anybody help me please.
Try to run Firefox in safe mode. It might helps. But, when I tried, in safe mode, Firefox still checks for compatibility though. But give it a shot.
Press Win+R to open Run Window, type
firefox.exe -safe-mode
to open Firefox in safe mode.
Every time I upgrade, Firefox begins checking compatibility of add-ons every time it starts. And it brings up the “Hooray! Your Firefox is up to date” page every time too. How to fix?
Modified June 29, 2012 12:14:23 PM PDT by francob
http://support.mozilla.org/en-US/questions/916830
Pendekarlaut provided answer that worked for me:
1. Firefox orange button>help>Troubleshooting Information
2. Under Application Basics, click Open Containing Folder
3. there will be prefs.js, user.js and sessionstore.js
4. Delete all 3 files
5. restart and done
wait. wouldn’t that be resetting firefox settings to default?