To provide some clarity on this, it likely isn't targeting specifically non-Chrome browsers.
Disclaimer: fmr Googler, used to work on YouTube
Likely, this isn't necessarily targeting Firefox/Safari/Etc, but rather is using the UserAgent as part of a tuple with other factors. It _is_ however an anti-adblock measure meant to determine if the video is automatically getting skipped forward.
The reason on why changing your useragent "fixes" the problem, is that you're changing the tuple and the anti-adblock system won't serve the code-at-issue until it determines whether you'd be a good candidate for the experiment.
Secondarily, YouTube has no financial incentive to actively punish non-chrome useragents. They make money in their division by serving ads, regardless of the useragent.
Disclaimer: fmr Googler, used to work on YouTube
Likely, this isn't necessarily targeting Firefox/Safari/Etc, but rather is using the UserAgent as part of a tuple with other factors. It _is_ however an anti-adblock measure meant to determine if the video is automatically getting skipped forward.
The reason on why changing your useragent "fixes" the problem, is that you're changing the tuple and the anti-adblock system won't serve the code-at-issue until it determines whether you'd be a good candidate for the experiment.
Secondarily, YouTube has no financial incentive to actively punish non-chrome useragents. They make money in their division by serving ads, regardless of the useragent.