The Chrome feature is not limited to the "screen size" (actually the window size), which is also possible with the Firefox Inspector, as suggested in a comment from Noitidart , and reported here for completeness:
- You can press
Ctrl + Shift + M (will open "Responsive Design") - Also available from "Main Menu"> "Developer"> "Fault-tolerant Design"
- Select the Responsive Design button on the toolbar toolbar.
(additional links about this in this link Responsive Design>)
Chrome also emulates a User Agent instead, for example, to run certain JS UA checks that allow you to use special device discovery features created by web application authors.
Currently, Firefox does not have this capability initially , but it has been requested several times in the official community and seems to be in development:
In any case, you can compensate for some additions, for example:
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