Recently, Firefox Picture-in-Picture has gained Subtitles and Captions support for videos. If you’ve found captions or subtitles text is either too small or large, here is how you can adjust the font size according to your convenience.
Firefox Picture-in-Picture is available with subtitles and Captions support
In case you don’t know, Picture in Picture supports captions for WebVTT format and for the following popular and other video sites:
- YouTube
- Amazon Prime
- Netflix
The feature support is enabled and available out of the box.
If you’re using a stable version, you may have to turn on hidden preference “media.videocontrols.picture-in-picture.display-text-tracks.enabled“ in about:config.

How to change or adjust the Font size of Subtitles and Captions in Firefox Picture in Picture mode
If you’ve set your monitor display Scale larger to see bigger text, you may want to change the way Picture in Picture displays subtitles on your screen. Here is how you can do that Irrespective of whether you’re using Firefox on Windows, Mac, or Linux the below method works.
Note: The issue with the Captions size can also occur when you resize the PiP window.
- Open Firefox
- Visit about:config
- Check “Warn me when I attempted to access these preferences” and click “Accept the Risk and continue”
- Copy and paste the following preference name, click on the pencil icon, and type font size as small or large.
media.videocontrols. picture-in-picture. display-text-tracks. size

- Click on the tick mark to save after that
Note: By default, the value was set to medium.
Head to YouTube or any other site that supports Captions and Subtitles in Firefox Picture in Picture mode and turn them on.
The PiP captions appear as per the size you’ve set above.
If you didn’t like the change, you better keep font size as medium unless you have got a visibility issue where you can fix that by setting pref. value to large.
Note: The above preference exists and works in Firefox 101. According to the Firefox release calendar, version 101 is expected to ship on May 31, 2022.
Final words:
Mozilla to allow Firefox users to change Picture-in-Picture captions or Subtitles size in Firefox version 101 or later.
What’s your take on Firefox’s Picture-in-Picture mode? Have you liked it more than Chrome? Let us know in the comments below.
More on Firefox:
Firefox 99 is out, here is what’s new and changed
Firefox 100 on Windows 7 requires KB4474419 Update
Firefox 98 arriving today: here is what’s new, changed, and Fixed
How to restore download Prompt in Firefox 98
Mozilla Firefox gets Windows 11 Style Scrollbars