Smart TV ACR study: Samsung, Vizio opt-outs fall short

Turning off tracking on your smart TV may not do what you think. A new study from Northeastern University tested 12 smart TVs from 10 brands and found that on Samsung and Vizio sets, switching off automatic content recognition (ACR) did not stop the TVs from sending ACR-style traffic. On Vizio, the opt-out had no visible effect at all.

ACR is the technology that lets a TV identify what is on screen, by sampling the picture or the sound, so the maker can build a viewing profile for ads and recommendations. The researchers say 82% of US households now have an ACR-capable smart TV. Their paper, called Watching the Watchers, was covered by Ars Technica on October 21 and by SamMobile and Techlicious this week.

What the smart TV ACR study tested

The team, led by Ilgar Mammadov with Het Rutul Joshi, Daniel J. Dubois and David Choffnes, looked at eight smart TV operating systems that together cover about 95% of the US market: Samsung's Tizen, Roku, LG's webOS, Vizio's SmartCast, Google TV, Amazon's Fire TV, VIDAA and Xumo. The 12 TVs came from Amazon, Hisense, LG, Roku, Samsung, Sony, Supersonic, TCL, Vizio and Westinghouse.

Each TV was tested in 10 situations, including an antenna broadcast, an HDMI input, Netflix, YouTube, Tubi, the maker's own streaming service, screen mirroring and sitting idle. Every scenario ran 30 times with ACR switched on and 30 times with it switched off, for 5,943 experiments in total. The researchers watched the network traffic each TV sent and looked for the repeating patterns that ACR produces.

What smart TVs track when ACR is on

With tracking allowed, every operating system the team could analyse tracked live TV from an antenna. HDMI input, which covers game consoles and streaming sticks, was tracked on five of seven systems, but not on Roku or Vizio's SmartCast. Most TVs also tracked their maker's own streaming service, with Fire TV and Google TV on Sony as the exceptions.

Some results are reassuring. No TV in the study tracked Netflix or YouTube. Tubi was tracked on Samsung's Tizen (in 29 of 30 runs) and on Google TV on Sony and VIDAA. Only VIDAA tracked screen mirroring. Vizio's TVs sent ACR-pattern traffic even when they were sitting idle.

Samsung and Vizio opt-outs fall short

Opting out worked fully on four systems: LG's webOS, Google TV on Sony, VIDAA and Fire TV. Samsung and Vizio were the problem cases.

On Samsung, ACR-style traffic carried on in all 30 opted-out runs of Samsung's own streaming service, in 41 of 60 antenna runs, 18 of 30 HDMI runs and 6 of 30 Tubi runs, plus a handful of idle, Netflix and YouTube runs. That is notable because an earlier study in 2024 found Samsung's opt-out did work.

On Vizio, the opt-out had no observable effect. The TVs kept sending the same traffic to an Amazon Kinesis endpoint in 100% of opted-out runs. Roku's opt-out does not cover The Roku Channel, though Roku discloses that in its terms, and TCL's Roku TVs show it in settings.

There is an important caveat. The traffic is encrypted, so the researchers cannot see exactly what was sent, and they describe the findings as potential privacy violations. A TV maker could, in theory, be receiving the data and throwing it away. Mammadov told Ars Technica that is unlikely, saying: "Transmitting data only to throw it away is an inefficient way to honor an opt-out." He added that whether it is a bug or not, "the outcome for users is the same: Their opt-out choice is not reflected in the TV's behavior." Ars said it had contacted Samsung and Vizio, and neither had answered at the time of its report.

How each TV recognises what you watch

The study also worked out how the systems spot content. Samsung's ACR is video-based: the traffic vanished when the screen showed only black. LG uses audio-based ACR from Alphonso, and ACR traffic dropped by 97.3% when the sound was off. Sony's Google TV uses video-based ACR from Samba TV.

VIDAA, the TV system developed by Hisense, had the worst security finding. It sent ACR results unencrypted to the ad company Unruly, and the researchers found a server that exposed more than 57 million detection results from over 1 million TVs, sorted into 82 categories. That has been partly fixed, as a login is now required, but the data is still sent unencrypted. Vizio's free WatchFree+ service also leaks the titles of shows being watched through unencrypted network lookups to the streaming partner Amagi.

How to turn off ACR on your smart TV

Menus vary by model and year, but these are the main paths. On Samsung, go to Settings, All Settings, General and Privacy, Terms and Privacy, then turn off Viewing Information Services (on older models, look under Support, Terms and Privacy, Privacy Choices). On LG, go to Settings, All Settings, Support, Privacy and Terms, User Agreements, and turn off Viewing Information, which covers Live Plus.

On Roku TVs, go to Settings, Privacy, Smart TV Experience and uncheck Use Info from TV Inputs. On Vizio, go to Settings, All Settings, Admin and Privacy, then turn off Viewing Data. On Sony Google TV models, turn off Samba Interactive TV in the settings. On Fire TV, go to Settings, Preferences, Privacy Settings and turn off Collect App and Over-the-Air Usage Data.

Based on the study, these switches are worth flipping on LG webOS, Google TV on Sony, VIDAA and Fire TV, where they worked. On Samsung and Vizio they may not be enough. The researchers' strongest advice is to keep the TV itself offline and use a separate streaming box or stick for apps. A disconnected TV cannot send ACR data at all. They have also published a blocklist of the tracking domains they found, which you can add to a network-level ad blocker.

Smart TV tracking and the law

TV makers have been in trouble over ACR before. In 2017 Vizio paid $2.2 million to settle charges from the US Federal Trade Commission and New Jersey that it tracked viewing without consent. Texas Attorney General Ken Paxton has sued Samsung, Hisense, LG, Sony and TCL over ACR. SamMobile reports that Samsung settled in February 2026 and agreed to ask for consent before collecting viewing data, which is why the new results for Samsung stand out.

What it means

Smart TVs are cheap partly because viewing data is valuable, and this study shows the off switch is not always reliable. If you own an LG, a Sony Google TV, a VIDAA set or a Fire TV, the opt-out appears to do its job. If you own a Samsung or Vizio, switch it off anyway, but the safest fix is simple: take the TV off Wi-Fi and stream through a separate device.