Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

Start your Computer in safe mode with networking. Then start Firefox. Try Safe websites. Is the problem still there?

Starting The Computer In Safe Mode;
Free Online Encyclopedia

Tried both with negative results. I can use other browsers without any issues but I prefer Firefox for gaming.

I've called for more help.

Firefox in Safe Mode means the problem is not Firefox. The computer in Safe Mode means it's not another program.

So it could be the update. Do you know which one it was?

One of the headline changes in Firefox 48-49 is e10s, which separates the browser interface process from the page content process. The performance impact of this can vary a lot between systems, so it would be helpful to know whether you have this feature turned on. To check that, either:

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, check the row for "Multiprocess Windows" and see whether the number on the left side of the fraction is greater than zero. If so, you are using e10s.

If you are using e10s:

To help evaluate whether that feature is causing this problem, you could turn it off as follows:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste autos and pause while the list is filtered

(3) Double-click the browser.tabs.remote.autostart.2 preference to switch the value from true to false

Note: the exact name of the preference may vary, but it will start with browser.tabs.remote.autostart

At your next Firefox startup, it should run in the traditional way. Any difference?

If that helps, it might be a negative interaction with one of your extensions, or a system setting, or ???

Checked that, fraction is 0/1. It also says on that line disabled by add-ons. I have only 3 active add-ons, Adobe Decryption module, Shockwave Flash and Open H264 Video Codec. I do know some add-ons can clash and cause problems so I try to keep those to a minimum. I do use the Add Blocker and Screen Shot modules as well but these are the Firefox add-ons.

Sometimes an update will corrupt the program folder, so this is worth a try:

Clean Reinstall

We use this name, but it's not about removing your settings, it's about making sure the program files are clean (no inconsistent or alien code files). As described below, this process does not disturb your existing settings. You do not need to uninstall Firefox first.

It only takes a few minutes.

(A) Download a fresh installer for Firefox 49.0.2 from https://www.mozilla.org/firefox/all/ to a convenient location. (Scroll down to your preferred language.) Choose the "Windows" version (32-bit) rather than the 64-bit version for maximum plugin compatibility (and of course for 32-bit Windows systems).

(B) Exit out of Firefox (if applicable).

(C) Using Windows Explorer/My Computer, rename the program folder as follows:

32-bit Firefox on 64-bit Windows: Rename

C:\Program Files (x86)\Mozilla Firefox

to

C:\Program Files (x86)\OldFirefox

Other combinations: Rename

C:\Program Files\Mozilla Firefox

to

C:\Program Files\OldFirefox

(D) Run the installer you downloaded in step (A). It should automatically connect to your existing settings.

Note: Some plugins may exist only in that OldFirefox folder. If something essential is missing, look in these folders:

• \OldFirefox\Plugins
• \OldFirefox\browser\plugins

Any improvement?