Are TikTok and X following you online? Find out here.

Markingpart of CalMatters, covers technology and its impact on our lives through investigative journalism, blueprints and tools.

As of 2020, readers use Black lightour pioneering website privacy inspector tool, to perform more than 18 million scans. Previously, Blacklight detected tracking pixels from Google and Meta. Today we’re announcing that it can scan for two more digital trackers: TikTok and X pixels.

A tracking pixel is a small piece of code added to a website that sends information about the site’s users to the platform that manages the pixel. This may include details of the user’s activities, such as their browsing activity, purchases and searches. A website that embeds a pixel often does so to inform its advertising campaigns on the platform that created the pixel. When its pixel is embedded in many websites, the platform can compile user data to build a detailed profile of their interests, behavior and other personal information. These profiles allow other businesses to buy ads from the platform to target user categories — although this data can also be used for other purposes.

When you search for a website in Blacklightnow it will report if it finds the TikTok pixel or X pixel. More detailed information about the specific data transmitted through pixels is also available by clicking “Learn more” in the top right corner of the results, then clicking the “download archive” link.

To develop these new features, we partnered with a group of computer science students in Brandeis University’s Software Engineering Capstone course. These students – Yiyou “Felix” fan, Jiawen “Zena” Hu, Hengye Li, Hongchen “Steven” Yang and Itquan “Frank” Zhang – researched and developed the features with the support of our product team.

Blacklight’s pixel detection features already powered ours Pixel hunting investigations that revealed that sensitive personal user information was being shared by government websites with Meta and Google, leading to lawsuits, removal of pixels from sites, and increased government scrutiny. These new features give a more complete picture of the digital privacy landscape by revealing tracking pixels from two more companies.

We hope these new features help you better understand what’s happening to your data while you’re surfing the web. While Blacklight can’t say exactly what companies like TikTok and X do with our data, it can provide a starting point for a deeper investigation into how that data is stored, shared and used on the web.

Have questions, suggestions, or need help understanding your Blacklight results? You can always contact us at blacklight@themarkup.org.