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Have you ever tried to install an old incompatible addon to Firefox 3? Since not every plugins/addons for firefox are not yet updated to be compatible with the latest Firefox, we often have to wait till they release a proper version. Its not liek the old plugin wont work in new Firefox. But they just have to check and make sure that every functionality of plugin is ok and it doesnot interfere with anyother features/addons. What if we dont want to wait that long? There is a solution. Actually not one, but many. I’l explain two possible and working solutions here.

1.Make your FireFox Compatible with old and new Plugins. (Disables compatibility check)

2.Edit the Addon / Plugin to make it acceptable by Firefox 3. You dont have to be a programmer for this. As simple as changing 2 to 3

I personally favors the second method. By which we can edit an addon / plugin to make it compatible to the new Firefox as we are not making any change to the browser.

First method is by which we can disable the compatibility check done by firefox through configuration. This trick will allow us to install any plugins. What we have to do is,

Type about:config in Firefox address bar and press enter.

It will show a warning as shown above. Click I’ll be careful, I promise! button to proceed. Do it only if you mean it! As setting any thing wrong may even cause something serious which makes you to reinstall the firefox. You just have to make sure that , you wont experiment much or click carelessly. Its like registry in our windows system.

If you are really careful, you can proceed with the steps. Else , i strongly advice you to check the second method below. Ok, now if you decided to go with this step, you will be seeing a list of strings and values. Never mind it.

Right click anywhere in the page and select New -> Boolean

Type in extensions.checkCompatibility in the message box and click Ok.

Set value as false in the next message box and click Ok.

Again ,

Right click anywhere in the page and select New -> Boolean

Type in extensions.checkUpdateSecurity in the message box and click Ok. Set value as false in the next message box and click Ok.

Thats all. Now Restart Firefox and try installing old plugins. It will be installed without any error.

Now, there are two problems with this method. One is, it disables the compatibility check of Firefox for new addons. In other words, its a global setting and you cant make it narrowed to individual plugins. Second  is, its for a single system only. If you want to share the plugin to a friend, the friend also have to go through all these procedure to make it compatible in his system.

The second method is to edit the plugin to make it compatibile to new versions. Its simple as changing a value 2 to 3. I’l explain it step by step.

Lets take the example of installing a plugin called BookMark All which is a usefull plugin to bookmark all open tabs in a browser window. This particular plugin is not compatible with Firefox 3 as of now. If you try to install it, it will show the error message as shown below.

Now , follow these simple steps. You can also check the How-To video given here to see how it works.

1. Right click the Plugin / Addon link and save the file (a .xpi file) to your system.

2. Open a winrar any such tool and drag and drop the addon file to it. Optionally you can also rename the file to .rar or .zip and open it.

3.It will contain a file and a folder. Drag and drop the install.rdf out of the archive. And open it with notepad.

4.Find the line

<em:maxVersion>2.0.0.*</em:maxVersion>

5.Replace the value 2.0.0.* with 3.0.1.* . Save and close the file. The value 3.0.1.* was set to work with the Firefox version 3.0.1. To make it work with higher versions just put the value acording to it. If the firefox version is 4.1 put the value as 4.1.*.* . Or you can always put a higher value like 10.0.0.* to make it work for a few years until firefox V10 is released .

6. Put the saved file install.rdf back into the archive. If you have changed the .xpi file to .rar or .zip , rename again to .xpi.

7.Drag and drop the .xpi file into an open firefox window and installation will start without any problem.

Check the video below to see how the second method is done.

Got a better method? Let me know. Comment it!