“More than just being creepy, it’s a huge violation of privacy,” said Cooper Quintin, a privacy advocate for the Electronic Frontier Foundation, a digital rights nonprofit that also offers the anti-tracking tool Privacy Badger. “People need to be able to read things and do things and talk about things without having to worry that they’re being watched or recorded somewhere.”

We took a close look at four free privacy tools: Ghostery, Disconnect, RedMorph and Privacy Badger. We tested them with the Google Chrome browser on the top 20 news websites, including Yahoo News, CNN, The Huffington Post and The New York Times.

The tracker busters generally work in similar ways. You download and install an add-on for a web browser like Chrome or Mozilla Firefox. The anti-tracking companies each compile a list of known web domains that serve trackers or show patterns of tracking services. Then when someone connects to a website, the tools prevent the browser from loading any element that matches their blacklist.

Ghostery, a popular tracker blocker, was the most difficult to set up. When you install it, it asks you to manually select the trackers you want to block. Our problem with that approach is that there are hundreds of trackers, and most consumers probably won’t recognize most of them, putting the onus on users to research which specific services they might wish to block.

Scott Meyer, the chief executive of Ghostery, said this had been a deliberate design choice. When trackers are blocked, parts of websites may not function, so it is less confusing to let users experiment and decide which ones to block on their own, he said.

“We block nothing by default,” he said. “That’s in direct contrast to other companies who are saying, ‘We’re turning everything off and let you turn whatever you want back on.’ That’s way too complex for users.”

The tracker blocking tool RedMorph takes the opposite approach. It blocks every tracking signal it can detect and lets people decide which ones to allow. For parents concerned about their children’s Internet use, RedMorph also offers a service to filter out certain sites or block certain swear words or other language they find inappropriate.