Developers should avoid relying on unload event because it will not fire whenever a page in background state (i.e. visiblityState equal to hidden) and the process is terminated by the mobile OS.
This part reads poorly:
... not fire whenever a page in background state ... and the process is terminated ...
This should probably read:
... not fire whenever a page is in a background state ... and the process is terminated ...
Grammar typo in the note at the end of the Introduction. https://w3c.github.io/beacon/#introduction
This part reads poorly:
This should probably read: