I bought a smart TV two years ago. It was on sale. Great picture. Then I started seeing ads for the exact shows I had been watching on a completely different streaming app. That was not a coincidence. The TV was watching me watch TV.

It is called Automatic Content Recognition or ACR. Your TV takes screenshots of whatever is on screen — cable, streaming, game console, even a DVD — and sends them to the manufacturer. They identify the content and sell that data to advertisers.

How ACR Works

ACR analyzes pixels on your screen a few times per second. It is not recording video. It is creating fingerprints of what you watch — tiny data snapshots that can be matched against a database of known content. The TV does not know you are watching “The Office.” It knows it saw a pattern of pixels that matches a known fingerprint for “The Office.”

This data gets packaged with your TV’s advertising ID and sold to ad networks. Those networks connect your TV viewing to your phone and laptop through your home IP address. That is how an ad for a show you watched on your TV shows up on your phone.

How to Turn ACR Off

Every brand calls the setting something different:

• Samsung: Settings > Support > Terms & Policies > “Viewing Information Services” — uncheck all boxes.
• LG: Settings > All Settings > General > “Live Plus” — toggle off.
• Sony/Android TV: Settings > Device Preferences > “Samba Interactive TV” or “Samba TV” — disable.
• Vizio: Settings > System > Reset & Admin > “Viewing Data” — toggle off.
• TCL/Roku: Settings > Privacy > Smart TV Experience > uncheck “Use information from TV inputs.”
• Amazon Fire TV: Settings > Preferences > Privacy Settings > “Collect App and Over-the-Air Usage Data” — turn off.

This took me about two minutes. I wish I had done it on day one.

The Other Privacy Settings Worth Changing

While you are in the settings menu, disable advertising personalization and reset the advertising ID. This prevents the data already collected from being attached to your new viewing habits. Also disable voice recognition if your remote has a microphone — those voice clips are sometimes reviewed by human contractors.

Your TV will still work. The picture quality does not change. The apps still stream. You just stop being the product.