YouTube is continuing its ad blocker crackdown by testing server-side ad injection.
Typically, a YouTube video will play and then YouTube pauses the video to run an advertisement. Ad blockers can generally bypass the ad by blocking JavaScript that YouTube uses to inject the ads. With server-side ad injection, the user is fed one continuous stream of video with the ad included, thus bypassing the ad blocker.
The change was first spotted by SponsorBlock, an ad blocker that uses crowd-sourced timestamps to block ads based on when they appear in the video. Server-side ad injection breaks SponsorBlock entirely. For now, the developer is filtering out submissions from people who spot server-side ads to avoid messing up its existing database, but it's looking for solutions.
"If YouTube displays any UI such as a clickable link, that means it has to know how long the ad is. SponsorBlock could find this data as well," it says. "There is also the feature for clicking on a timestamp in a comment that would need to know the duration of the ad, so it should be findable somewhere, it just might be kind of hard."
In a statement provided to BleepingComputer, YouTube reiterated that "ad blockers violate YouTube's Terms of Service, and we've been urging viewers for some time to support their favorite creators and allow ads on YouTube or Try YouTube Premium for an ad-free experience."
YouTube has been going after ad blockers for more than a year. Last year, it experimented with a pop-up message that stopped video playback until either the ad blocker was disabled or users signed up for YouTube Premium. More recently, people with ad blockers installed found that videos were randomly skipping to the end or staying muted no matter what they did.
Turning off ad blockers largely fixes these issues, though ad blockers have also done a pretty decent job of adapting.