The button should be a PageAction, which would make it have a dot in Chromium on affected pages (grayed out otherwise) and on Firefox/Vivaldi, make it appear in the address bar.
Actual behavior
It is a normal button, so it appears on all sites, including those it does not affect. Cluttering and confusing UX.
Steps to reproduce the problem
Install the extension in mentioned browsers, watch it's behaviour.
Expected behavior
The button should be a PageAction, which would make it have a dot in Chromium on affected pages (grayed out otherwise) and on Firefox/Vivaldi, make it appear in the address bar.
Actual behavior
It is a normal button, so it appears on all sites, including those it does not affect. Cluttering and confusing UX.
Steps to reproduce the problem
Install the extension in mentioned browsers, watch it's behaviour.