Hi

You can install this add-on in the desktop versions of Firefox.

It didn't solve the problem! Not even showing Random user agent

Hi

Are you able to install it from?:

https://addons.mozilla.org/en-GB/firefox/addon/random_user_agent/

Still doesn't work after downloading it it says "no app to open xpi files" please what version used to have it let me download it, or it's also removed from the version

You do not open the XPI file (actually this is a ZIP archive), but you install the extension. See:

• https://support.mozilla.org/en-US/kb/find-and-install-add-ons-add-features-to-firefox

Just tell me the version that has this feature let me download it and save me from all these stress!

Firefox does not come with this add-on pre-installed. You will need to go the add-ons site and install it from there, as per cor-el's answer.

How do I open the XPI file then?

There are a few random user agent extensions at AMO. https://addons.mozilla.org/firefox/search/?q=Random%20user%20agent

The vast majority of Extensions hosted at AMO are made by a third-party extension author or company and none of those random user agent extensions are made by Mozilla.

How do I open xpi files

Hi

You do not need to - the install button on the website will download and install the .xpi file for you.