Could you try starting Firefox in its Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Use Troubleshoot Mode in Firefox.

With Firefox fully closed, you can hold down the Shift key when starting Firefox.

A small dialog should appear. Click "Start in Safe Mode" (not Reset).

Any difference?

If Firefox is visible, go ahead and disable Firefox's use of hardware acceleration as a workaround for a possible graphics card driver software incompatibility.

"3-bar" menu button (or Tools menu) > Options > Advanced

On the "General" mini-tab, uncheck the box for "Use hardware acceleration when available"

That will be in effect the next time you exit and start Firefox back up.

Another thought: if Firefox is restoring preview windows and tabs, it could be a full screen media player. The Esc key might help restore its normal size (at least for Flash). The standard key to toggle web pages between full screen and regular view is the F11 function key.

Thanks... Issue resolved...

John, thank you for reporting back.

You may get video card updates with your monthly Windows updates or at other intervals, so you could try switching hardware acceleration back on after your next update. It mostly affects 3D and animations.

THANK YOU!

Turning off hardware acceleration fixed it for one of my client's computers too.

hello, other users with this problem all had an embedded intel hd graphics card with an old driver present. in case this also applies to you, here would be a link to update the driver, which in turn should also address the black firefox problem.

Intel HD 2000/3000: 32bit https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=23763 64bit https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=23764

Intel HD 4000: 32bit https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=24328 64bit https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=24329

What if you can't see any menus? See screenshot.

aujpoj, i've answered that in your question at https://support.mozilla.org/en-US/questions/1025733 you can launch into firefox save mode by pressing the shift-key while firefox is launching...

Mine is doing that today too. Black screen upon startup.

Internet Explorer works fine though.

Have tried uninstalling & reinstalling. No luck

Perfect solution! Thanks so much!

Hi amysovereign, try using Firefox's Safe Mode to disable Firefox from using hardware acceleration, as described in this post: https://support.mozilla.org/questions/1025438#answer-640569

Or if you update your graphics card driver software, that may fix it. See: https://support.mozilla.org/questions/1025438#answer-641090

Note that in order to do that update, you may need to first research which Intel chipset is in your system.

The safe mode solved the problem-thanks!

When I start firefox black screen come up. Restarting did not help. When tried to start firefox in safe mode by clicking shift and forefox. Safe mode did not start. - Solved when installed Intel update