Laptop, Desktop, or DIY? If not DIY, what make and model? What graphics card and driver version? Did you ever check in Windows update under the optional update section?

Have you tried Firefox in Troubleshoot Mode?

Desktop, DIY

GPU RX6400 driver version [23.20.17.03-231016a-398307C-AIB] AMD driver version for windows [31.0.22017.3004]

Windows 10 professiona N 64 bit 22H2

I have tired Firefox in troubleshoot mode I have checked update under optional updates, there is none and everything is up to date

You can check the codec support in the "Help -> More Troubleshooting Information" (about:support) page, you may have to play a video to initialize this section.

• Media -> Codec Support Information
• https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox

Under HEVC and AAC I have "not supported" on both sides

H264 is "supported" on both sides

Does youtube work with the h264ify extension installed?

Try installing or updating the "VP9 Video Extensions" and "AV1 Video Extension" from the Microsoft Store then reboot.

Try running the System File Checker tool:

sfc /scannow

Ok I manage to solve it sfc show two corrupted dll files What I did in the end was as follow:

sfc /scannow DISM /Online /Cleanup-image /StartComponentCleanup DISM /Online /Cleanup-image /RestoreHealth reboot sfc /scannow uninstalled media feature pack reboot sfc /scannow reboot sfc /scannow installed media feature pack reboot

and it works