Blacklight update: are TikTok and X tracking you across the internet?

The Markup, working with computer-science students from Brandeis University, expanded its Blacklight website-tracking scanner to detect embedded TikTok and X tracking pixels in addition to the Google and Meta trackers it already identified. Since its 2020 launch, Blacklight has been used for more than 18 million scans of websites for hidden trackers, and the new detection capability lets users check whether sites they visit are feeding their browsing, purchase, and search activity to TikTok or X via pixel-based tracking.

The update does not itself reveal how TikTok or X use the data collected through these pixels, and the piece frames the tool's expanded coverage as a starting point for further investigation into how tracked data is stored, shared, and used across the web, rather than a complete accounting of either platform's data practices. It positions the release as part of The Markup's ongoing Pixel Hunt series examining commercial tracking infrastructure.