Is your smart TV keeping notes on what you watch — and how do you turn that off?

Most smart TVs use automatic content recognition (ACR) to fingerprint whatever is on screen — streaming, antenna, cable box or game console — and that viewing record can be used to target ads. You can switch the viewing-data collection off in about five minutes; here is where the setting hides on Samsung, LG, Sony, Vizio, Roku TV and Fire TV.

You watch a few beginner tennis guides on the TV, and then tennis-racket ads start following you around the web. Short answer: yes, most smart TVs can do exactly that. They use a feature called automatic content recognition, or ACR, which fingerprints whatever is on screen and matches it to shows, ads and games — and you can switch that viewing-data collection off in about five minutes.

ACR does not only watch your streaming apps. It can also notice what comes in from an antenna, a cable box or a game console, and that viewing record can then be used to aim ads at you. Here is where to turn it off, brand by brand:1.

Samsung: open Settings, All Settings, General & Privacy, then Terms & Privacy, and turn off Viewing Information Services and Interest-based Advertising.2. LG: open Settings, General, System, then Additional Settings, turn off Live Plus, and under Advertisement switch on Limit Ad Tracking.3. Sony: open Settings, then All Settings, and turn off Samba Interactive TV.4.

Vizio: open Settings, All Settings, then Admin & Privacy, and set Viewing Data to off.5. Roku TV: open Settings, Privacy, then Smart TV Experience, uncheck Use Info from TV Inputs, and under Privacy, Advertising, switch on Limit Ad Tracking.6. Amazon Fire TV: open Settings, then Privacy Settings, and turn off the tracking and interest-based ad options there.Pro tip: Check these switches again after a big software update, because updates can quietly turn them back on.

And simply unplugging the TV is not a full fix — some TVs keep capturing data while offline and upload it the next time they connect.Ad’s take: Your living room should be for relaxing, not taking notes for advertisers. Five quiet minutes in Settings, and your TV goes back to just being a TV.