Wrong title, if it's "File System Access API (still Chrome-only as far as I can tell)" then it should read "A browser is the sandbox".

At the risk of sounding obvious :

- Chrome (and Chromium) is a product made and driven by one of the largest advertising company (Alphabet, formally Google) as a strategical tool for its business model

- Chrome is one browser among many, it is not a de facto "standard" just because it is very popular. The fact that there are a LOT of people unable to use it (iOS users) even if they wanted to proves the point.

It's quite important not to amalgamate some experimental features put in place by some vendors (yes, even the most popular ones) as "the browser".

I stand by a policy that if a feature in one of my projects can only be implemented in Chrome, it's better not to add the feature at all; the same is true for features which would be exclusive to Firefox. Giving users of a specific browser a superior experience encourages a dangerous browser monoculture.