Recognize browsers that disallow sync XHR in page dismissal

[michal1106]

Hi There,

We were wondering if there's a way to know about a browser if it dis/allows sync XHR in page dismissal

Chrome disallows it since v.80 - https://www.chromestatus.com/feature/4664843055398912
Safari start disallowing lately (if we detected correctly, it started on v.13.1)

We couldn't see any documentation about how to check if the disallow is enabled and we struggle with browsers and versions in order to understand if the XHR in page dismissals is restricted

Do you have a suggestion / support for this?

Thanks,
Michal