You can go to Option->Advanced->Update and then select the button Check for updates but let me choose whether to install them.

Riya, that is not going to fix anything for the person who started this thread! If anything, the correct choice would be Never check for updates (not recommended: security risk) which is close to what the mentioned pref does.

katlomas, Please verity that pref made it into the prefs.js file in your Profile folder by examining the contents of prefs.js. One slight error with that file or the wrong location, and that pref wouldn't have been written to the prefs.js file upon the first launch after inserting that pref.

Also, typically I also add this to the user.js file. user_pref("app.update.url", " ");

You can also delete the maintenanceservice.exe file and the maintenanceservice_installer.exe' file from the Firefox program files folder. I had that Maintenance Service update one of my Firefox installations unexpectedly a few months ago, much to my surprise. For the most part, I don't update Firefox, but rather add each new version when it is released. I keep the older versions around and have every version from Firefox 20.0.0.20 to the latest Nightly version installed; each with their own Profile.

Hi, the-edmeister. You are right; the suggestion offered by Riya is of no use because that button is checked and always has been. I have deleted the two maintenance files you mention and looked at the pref.js file. I get an error message : see the attached image. No idea what to do about this. I think for now I'll check off Never check for updates, because I don't want any updates! Thanks for your help.

don't double-click the file (which would execute it), but right-click & edit it with a text editor... since these settings are profile-specific, another user account on your machine could override that and update nevertheless also.

As philipp mentioned, if you have other user accounts on that PC and/or additional Profiles in your main user account, another Profile can update Firefox. You need a user.js file in every Profile with that pref to lock out any accidental updates from happening.

Never check for updates ... isn't infallible, the Maintenance Service can override that "Never check ..." preference, which is why deleting that "Service" is important to avoid "pushed updates" that Mozilla enables from time to time.

Also, you really should open prefs.js in a text editor program via a right-click and using Open with > Notepad (or Wordpad) to verify that pref made it to the prefs.js file. If user.js isn't recognized in Firefox [newer versions of Windows have a nasty tendency to add .txt to the .js files which are created in Notepad, and with the default in Windows to "hide known suffixes", a user nay not even realize that the file has that extra suffix AND Firefox won't use that file named like this - user.js.txt] or a pref in user.js is incorrect [like a relatively minor mistake in context] it won't make it to prefs.js - which means the pref won't do anything. Been there, done that more times than I care to remember.

Quite honestly, I use ChromEdit Plus to create the 3 "user" files and for editing them, rather than mess around with a text program and create those files and paste them into the Profile folder. Saves me a lot of time each year, what with the number of Profiles I create each year, and it cuts done on stupid errors or mistakes I have made in the past. http://webdesigns.ms11.net/chromeditp.html