Firefox font kerning disabled

I’ve had a weird default font on firefox for about a year now. I’ve tried to get rid of this by reinstalling, updating windows and firefox, and going through various default font settings to reset them. It happens on a variety of websites that use a default font, but I’m not sure of any more specifics.

Here’s what it looks like right now:

And here’s what it should look like:

I’m stumped at how to get it back to the default. Any recommendations?

How does it look in Troubleshooting Mode? In a new profile?
https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

Thanks for the recommendations! I’ve gotten mixed results. A new profile doesn’t affect the problem, but troubleshooting mode does solve it. I went through disabling add-ons and everything that they list in those guides, but nothing seems to fix it. Unsure what else troubleshooting mode changes that could help here, but I’m ready to try whatever else you suggest!

Since troubleshooting mode helps but a new profile doesn’t then the issue probably isn’t add-ons (unless you are in an enterprise environment and your administrator is forcing add-ons). See the " What does Troubleshoot Mode disable?" section of the troubleshooting page. Do you have userChrome and userContent customizations?

If you can’t figure it out from that page there is a more active user support group on the Matrix. See https://wiki.mozilla.org/Matrix . Join the Firefox Desktop Community room, #firefox:mozilla.org .