Nearly three years ago we launched Blacklight, an online tool that allows users to enter any website and find out what tracking technologies are present and who gets the visitor data they collect. 

This month, Blacklight hit a significant milestone: The tool has successfully conducted more than 10 million scans. Seven million of those scans were completed in just this past year. 

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Try out Blacklight here. Enter a website, and Blacklight will scan it for user-tracking technologies — and who’s getting your data.

Enter a URL for Blacklight to scan

Blacklight was created with one guiding premise: that it would be more powerful to show people, in real time, how they were being tracked online than to merely tell them such tracking was happening. Led by former Markup senior data engineer Surya Mattu, a team of programmers and journalists spent 18 months building Blacklight and released it in conjunction with a Markup story. Surya and investigative reporter Aaron Sankin scanned 80,000 popular websites with Blacklight and found that nearly 90 percent of them had some sort of third-party tracker. Aaron also published a guide for readers on what to do if, after using Blacklight to scan a website, you find the results to be horrifying. 

In addition to going to our Blacklight tool and typing in the website you want to scan, it’s also possible to access Blacklight programmatically, which is what Surya and Aaron did to scan those 80,000 websites. While we haven’t written official documentation on how to do this, we believe people are already using Blacklight to conduct automated scans on websites at a large scale. If you currently work with Blacklight in this way, or are interested in doing so, we’d love to hear from you as we think about what’s next for Blacklight: hello@themarkup.org.

To recognize this month’s milestone, we want to highlight just a few of the projects that have used Blacklight: 

• Alexis R. Rosenblat used it to check patient intake software for STAT news
• The Opioid Policy Institute and Legal Action Center found addiction treatment and recovery sites tracking users
• ProPublica saw trackers on the sites of online pharmacies that sell abortion medication 
• Human Rights Watch caught ed tech violating children’s privacy
• Organizations including the Electronic Frontier Foundation and ProtonVPN celebrated their privacy performance in Blacklight scans of their own sites
• Velislava Hillman used it to scan an ed tech site
• Mikal Jakubal found articles about trackers loaded with trackers
• Numerous academic studies, from measuring ed tech privacy standards to analyzing health-related sites, and much more. 

The pervasiveness of the tracking uncovered by Blacklight can feel daunting. But, like other Markup tools that followed, Blacklight gives people some degree of control over how they engage with the digital world. As Surya said at the time of Blacklight’s launch, “We want readers to have a sense of agency—not apathy.”