Blocking website trackers is easy. Several popular web browsers block ads and trackers by default, and there are plenty of third-party apps and browser add-ons that can fill in the gaps where needed. But have you ever wondered what, exactly, these helpful tools are actually blocking?
For an easy way to see everything a website tracks even before you visit it, and where that data is shared, we highly recommend checking out TheMarkUp.org’s web-based “Blacklight” tool. (You can also get this information via third-party software, browser blockers, or specially configured browser settings, but you have to first visit a site before they typically analyze it.)
How to use Blacklight
Here’s how it works: Open the Blacklight page, and then enter a URL into the “Enter a Website Address” bar and click “Scan Site.”
Here’s what the site does in the background (and anonymously):
Blacklight works by visiting each website with a headless browser, running custom software built by The Markup. This software monitors which scripts on that website are potentially surveilling the user by performing seven different tests, each investigating a specific, known method of surveillance.
After a few moments, the tables will display the results. This includes:
- How many ad trackers a site has
- How many third-party cookies Blacklight found
- The presence of trackers that can circumvent cookie blockers
- Session tracking
- Facebook social tracking
- Google analytics
Click the arrow next to any of these fields for more information. You can also download an archive of the results and see screenshots of the pages scanned by clicking “Learn more” next to the timestamp.
That said, don’t rely on Blacklight’s test results alone for vetting a website’s privacy.
A disclaimer at the bottom of the page says, “Blacklight results should not be taken as the final word on potential privacy violations by a given website. Rather, they should be treated as an initial automated inspection that requires further investigation before a definitive claim can be made.”
Basically, this tool can give you a good look at how a website tracks and shares your data, but it might not catch everything. While the scan results are helpful, and sometimes surprising, it’s best to use Blacklight in conjunction with a privacy-focused browser and other tracker-busting apps to keep your personal data private.