This is usually caused by a custom Windows theme (regedit hacks), try to uninstall it if you can. Always be careful installing .reg files as they can be difficult to undo.

Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or if userChrome.css/userContent.css is causing the problem.

• switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

@zeroknight I have no themes installed in windows. Nor I could Find a .reg files installed.

@cor-el That was first thing I did when I found the issue. and I have uninstalled and reinstalled Firefox multiple times to fix the issue too.

This this is happening with Windows 10 pro but not with Windows 11 pro.

I have other System with Windows 11 pro where I am not facing the issue.

Also chrome works just fine and is not facing any issue.

The work I do needs multiple browsers open at same time with multiple tabs. So I need Firefox too. Also I was always a Firefox user so I don't like to use chrome much colleagues suggests other browsers but it hurts my pride to leave Firefox.

The final thing I can think is that Firefox dialogue boxes uses a font which are not enabled in my system or I need to download since I can see button without text.

Or it could be something is blocking the whole UI output and just lets me see buttons.

It looks like Firefox's UI became corrupted because one of its core files is damaged. But since you uninstalled & reinstalled Firefox that doesn't sound like the problem.

I would disable ALL of the addons in Firefox then restart it & test all those buttons again. See: https://support.mozilla.org/en-US/kb/disable-or-remove-add-ons#w_disabling-and-removing-extensions

Also make sure the only theme enabled in the Themes area is the "System theme".

The font idea is a good point too. But the only way I could see that happening is if you deleted a important system font from Windows 10 which I don't think you did. And it appears more than the words are missing, the icons are missing too. Which tells me something in Firefox's UI became very damaged or parts of the UI are being blocked by one of the addons or a single file is damaged in the Firefox profile.

If disabling the addons doesn't work, you could try a Firefox Refresh but that will remove all your addons & themes, reset some preferences you made and a few other customizations. So please read what it does before using it. It makes these changes to your Firefox profile.

Firefox Refresh: https://support.mozilla.org/en-US/kb/reset-preferences-fix-problems

If you only want to target the Preference files (prefs.js, prefs.js.moztmp & user.js), look here: https://support.mozilla.org/en-US/kb/reset-preferences-fix-problems#w_solution-2-delete-firefox-preference-files

If none of that helps, you can create a new Firefox profile: https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles#w_manage-profiles-when-firefox-is-open

Which starts you off fresh. Then you can try slowly importing over your data to that profile by copying over specific files that contain the data you need & not the potentially corrupted files that are breaking the UI.

@NoahSUMO Done Again installing reinstalling. Removed profiles too. Changed profile. No add-ons anymore. (after reinstall never added one.) I am only using system theme as I don't like to create fancy stuff.

Already did a refresh.

(tested each time if issue is fixed but a big NO.)

I have come to conclusion that either previous worker sitting on my PC removed some fonts or Either this whole thing is working on updated language not updated on my PC. I will need some guidance to solve this. Please let me either know which fonts are used for the missing texts. (I can try installing them.) or which JavaScript or any Language is used for the same. ( I can update it to Needed Version. I doubt the PC will be able to handle the advanced version.)

Thanks a lot for all answers though. It broaden my horizons more.

Also sorry for bother mozilla suppport even though it is a clear issue with my PC.

Can you attach a screenshot?

• https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem
• use a compressed image type like PNG or JPG to save the screenshot

@cor-el sure. Here is screenshot. (Although I have shared screen record video in the google drive link).

I have marked the area in red square.

Thank you.