Firefox Tekoha Aty

Since April 5th I have lost spell check in the message pane of the emails I type on outlook.live.com It still works in the subject line, but not the message area.

Windows 10 pro 22H2 updated to end of March, when spell check was still working well. Firefox 137.1 English Canada Language selected (has worked well for years)

I go to outlook.live.com to read and answer my @hotmail.com emails.

When right clicking on a misspelled word in the message area I get only these options, Firefox does not give me the usual options.

I am currently having other problems on that site, clearing outlook.live.com cookies does not clear the problems.

Fix for RangeError: invalid language tag and client-side exceptions in Firefox on Linux

Hi everyone, I was experiencing persistent JavaScript errors in Firefox on Linux when loading certain modern websites (e.g., built with React or Next.js). The browser console showed messages like:

   RangeError: invalid language tag: "chrome://global/locale/intl.properties"

   A client-side exception has occurred (see the browser console for more information)
   React error #418 with minified stack traces

This happened even in Safe Mode, with all extensions disabled, cookies/cache cleared, and Enhanced Tracking Protection off. ✅ Root cause and fix:

Turns out the issue was related to missing or broken locale configuration in Firefox. To fix it:

   Open about:config

   Create a new string entry:

       Name: intl.locale.requested

       Value: en-US (or fr, en-GB, etc. — any valid locale)

   Restart Firefox

After adding this key, all affected pages started working correctly. The invalid "chrome://global/locale/intl.properties" error in intl.accept_languages disappeared as well — it seems that was just a side effect of the missing locale setting. 🔁 Summary:

If you’re seeing RangeError: invalid language tag and React crashes, try adding intl.locale.requested manually. This fixed the issue entirely for me on Linux.

Hope this helps others!