Every website you visit is quietly chatting with a whole crowd of companies you’ve never heard of. Blacklight lets you peek into the room and see exactly who’s there.
What Blacklight is
Blacklight is a free tool from The Markup, a nonprofit newsroom that investigates how technology shapes our lives. You paste in any web address, and it scans the site and shows you the tracking tech hiding behind the pretty pages. No account, no download, no fuss.1
What it finds
Blacklight looks for the usual suspects: ad trackers, third-party cookies that follow you from site to site, and social media pixels that quietly pass your visit along to Facebook, TikTok, and X. It also flags Google Analytics data heading to Google for advertising.
It goes deeper too. It can spot canvas fingerprinting, which builds an identifier from your device so you can be recognized even with cookies blocked. It checks for session recording, where a site replays your clicks and scrolls like a little movie of your visit. And it tests for keystroke capture by typing sample text into a site’s forms, without ever submitting them, then watching to see whether that text gets sent off before anyone hits a button.2
How to use it
Enter a web address, pick where you want the scan to come from (Ohio, California, or Europe) and whether to view the site as a phone or a desktop, then hit Scan Site. It usually takes 30 seconds to a minute.1 You can even scan a specific page instead of just the homepage, which is handy for checking a contact form or a login page.3
Try it on the sites you actually use: your doctor’s portal, your bank, your kid’s school, that recipe blog you love. Then try the same site from Europe and from Ohio and see whether it behaves differently.
What it can’t tell you
Blacklight is a snapshot, not a verdict. It only checks the page you give it, so it can’t see what happens behind a login. It can’t tell you why a site is doing something, and some canvas fingerprinting is really just bot detection, so a flag isn’t automatically a smoking gun.2 It also shows you who’s watching without stopping them, so once you know what’s lurking, a good tracker blocker and a privacy-minded browser are your next best friends.
Scan a WebsiteSources
- Blacklight — The Markup ↩
- How We Built a Real-time Privacy Inspector — The Markup, September 2020 ↩
- Announcing Three New Features for the Blacklight Privacy Inspector — The Markup, August 2023 ↩
