Type about:preferences#content<enter> in the address bar. Across from fonts and colors, press the Advanced button. On the bottom, turn on Allow Web Sites To Choose Their Own.

Fonts Information - Detected via Flash http://browserspy.dk/fonts-flash.php?detail=1

Mac You can check for corrupted and duplicate fonts and other font issues: http://www.thexlab.com/faqs/multipleappsquit.html - Font Book 2.0 Help: Checking for damaged fonts http://www.creativetechs.com/iq/garbled_fonts_troubleshooting_guide.html

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?

FredMcD said

Type about:preferences#content<enter> in the address bar. Across from fonts and colors, press the Advanced button. On the bottom, turn on Allow Web Sites To Choose Their Own.

It was already enabled. FredMcD said

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?

No difference, Safe Mode tried already.

Also h264 decoding is disabled, pushing my CPU to 30% when watching a video on Youtube (forced h264). And I've got an i7 4770k. I know this is a different problem, but I think is linked to this one.

I'm not sure why Firefox isn't using your GPU but for best results we need to figure out a way to get that working.

For comparison on Windows 7:

Adapter Description: Intel(R) HD Graphics 5500 Adapter Drivers: igdumdim64 igd10iumd64 igd10iumd64 igdumdim32 igd10iumd32 igd10iumd32 Adapter RAM: Unknown Asynchronous Pan/Zoom: none Device ID: 0x1616 Direct2D Enabled: true DirectWrite Enabled: true (6.2.9200.17568) Driver Date: 11-11-2014 Driver Version: 10.18.10.4013 GPU #2 Active: false GPU Accelerated Windows: 7/7 Direct3D 11 (OMTC) Subsys ID: 503617aa Supports Hardware H264 Decoding: Yes Vendor ID: 0x8086 WebGL Renderer: Google Inc. -- ANGLE (Intel(R) HD Graphics 5500 Direct3D11 vs_5_0 ps_5_0) windowLayerManagerRemote: true AzureCanvasBackend: direct2d 1.1 AzureContentBackend: direct2d 1.1 AzureFallbackCanvasBackend: cairo AzureSkiaAccelerated: 0

I'm not sure if there is a known issue with your ATI hardware/drivers, or whether some startup diagnostic failed and that's why acceleration isn't working for fonts. ???

Can you attach a screenshot?

• https://en.wikipedia.org/wiki/Screenshot
• https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

• use a compressed image type like PNG or JPG to save the screenshot
• make sure you do not exceed the maximum size of 1 MB

Does it make a difference whether hardware acceleration is enabled or disabled?

cor-el said

Can you attach a screenshot?

• https://en.wikipedia.org/wiki/Screenshot
• https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

• use a compressed image type like PNG or JPG to save the screenshot
• make sure you do not exceed the maximum size of 1 MB

Does it make a difference whether hardware acceleration is enabled or disabled?

Sorry, a screenshot of what?

You mean turning On and Off "use Hardware acceleration when available" from settings>Advanced? No, it does not make a difference at all.

I also use Thunderbird. The same page clearly shows: - Direct2D enabled: false - DirectWrite enabled: false - WebGL Rendering: false

Hi,

I have found the root cause of the problem. It's AMD drivers.

I went for a clean uninstall in safe mode via Display Driver Uninstaller and installed AMD Crimson 16.5.2.1 (previous version), now everything is back on! Firefox is smooth, and fonts can be finally admired.

See attached screenshots before and after. It's in Italian, but you can get the translated strings from pastebin or compare it to your system.

FYI the version of AMD drivers that was causing the problem it's not a beta, it's the last production version I get when I select my GPU (v16.5.3). I have installed v16.5.2.1 and it's all good.

Should this problem be reported to Firefox or AMD? Other browsers (Chrome) were rendering fine.

Thanks for your help anyway.

I'm not sure whether this is a known issue with the newer driver or not, but sometimes Firefox will disable a driver (or some features of a driver) if it causes a lot of crashes. You might look at the update again in a couple weeks after Firefox 47 is released since there aren't going to be any more fixes for Firefox 46.

That was very good work. Well Done. Please flag your last post as Solved Problem so others will know.