It has been alleged that YouTube is now directly injecting adverts into video streams to increase the difficulty of ad blockers blocking advertisements.
SponsorBlock is a third-party browser extension that uses crowdsourcing to gather information about which video parts are sponsored and which ones should be skipped.
According to SponsorBlock, server-side ad injection will prevent it from working, but fixes are on the way. Most significantly, it will also affect how well users' other YouTube ad-blocking tools work.
YouTube is currently experimenting with server-side ad injection. This means that the ad is being added directly into the video stream.
— SponsorBlock (@sponsorblock@fosstodon.org) (@SponsorBlock) June 12, 2024
This breaks sponsorblock since now all timestamps are offset by the ad times.
Server-side ad injection
The video player on a user's device loads and displays advertisements through client-side ad injection, which is currently used by YouTube.
advertising and the video stream are distinct, and the player is configured to play advertising at predetermined intervals while pausing the content.
The majority of ad blockers typically work by preventing the JavaScript scripts that are used to insert YouTube advertisements into the video stream. A little differently, SponsorBlock lets users skip sponsored sequences in videos by crowdsourcing information about various parts of the video.
The website for the extension states that SponsorBlock is an open-source crowdsourcing browser plugin and open API for skipping sponsor parts in YouTube videos.
"Using a privacy-preserving query system, users submit when a sponsor occurs from the extension, and the extension automatically skips sponsors it knows about."
Users receive a continuous stream with the adverts pre-integrated, thanks to server-side ad injection, which inserts the ads into the video stream before the content is sent to the viewer.
According to SponsorBlock, YouTube streams videos by breaking them up into smaller bits that are then combined to provide a seamless video watching experience.
The YouTube server delivers a playlist including both content and ad chunks when a user clicks on a video; the sequence in which these chunks are played is determined by a manifest file.
The fact that this method offsets timestamps for sponsored material and that the offset varies with the length of the adverts affects the functionality of SponsorBlocks.
Additionally, it makes it harder for ad blockers to detect the ads that are now a part of the continuous stream, which makes client-side injections that are easy to detect less effective.
Solutions and workarounds
As a preventative measure against data manipulation, SponsorBlocks claims to have blocked submissions from browsers that are experiencing server-side ad injection. When YouTube switches to server-side injection on a larger scale, though, this will no longer be viable.
The system is not yet ready, but in the future, the tool will try to determine the duration of ads using different detectable metadata and YouTube's UI features.
Potential countermeasures for ad blockers include creating more complex detection algorithms, utilizing metadata analysis, and applying cutting-edge pattern recognition to spot abrupt changes in audio or video that might be signs that an advertisement is about to play.
YouTube was contacted by BleepingComputer for a statement regarding its plans for server-side injection, but one was not immediately available.
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