Together, We Build a Better Web

A community-driven Web developer engagement initiative focused on the backward compatibility in Firefox. Documents, tools, latest updates & more.

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Mozilla shipped Firefox 77 Beta and Developer Edition today.

Since the COVID-19 pandemic is still creating huge challenges to many businesses and individuals around the world, Firefox developers have avoided including backward-incompatible changes other than JPEG image auto-rotation, which is known to be affecting Slack and other sites, but Google Chrome has the same issue because they have already shipped the same enhancement. Actually, the change to the image-orientation CSS property has not landed in Firefox 77 at this writing — it will probably be coming to the Beta channel next week.

The removal of Application Cache storage was initially planned for Firefox 77 but postponed.

Update: There’s one more change posted recently.

That’s it for Firefox 77.

Speaking of future releases, Firefox 78 will be the next Extended Support Release (ESR) for enterprises, so breaking changes will be avoided again. In the coming weeks, we’ll be documenting all the changes postponed due to COVID-19, which are going to be shipped with Firefox 79 or later.

We’re also busy working on the compatibility checker in our Firefox Developer Tools extension. The CSS support is coming soon. Stay tuned, stay safe!

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