Input lag is the amount of time between when a TV receives a signal and the display updates. Fighting games, action games, and other titles that require precise timing work best when input lag is very low. It can make the difference between feeling like you have total control over everything happening and needing to constantly compensate for what amounts to very tiny pauses that can throw off your game. Input lag generally ranges between 2 and 120 milliseconds for TVs, with the biggest differences not between different TVs but between any given TV's game mode and other picture modes. For example, if you play in the Theater picture mode on even the fastest TV, you are likely to experience lots of lag. We consider less than 20ms to be acceptable, but for a TV to qualify for this roundup, the input lag must be under 10ms. We previously used 20ms as our best-for-gaming threshold, but we've seen significant drops in input lag over time and adjusted accordingly. We test input lag using an HDFury 4K Diva 18Gbps HDMI matrix with an Xbox One X as a source. The matrix processes the source video to 4K, then transmits the picture to the TV with a black box overlaid on the center of the screen. A light sensor we place on the screen measures the box as it flashes, determining how long the TV takes between when the signal is sent and the picture changes, down to the tenth of a millisecond. The test has a floor of 1ms, and we've recently seen a few TVs that reach below that. The Diva can measure input lag with both 1080p and 4K pictures, and so far we've seen deviations between the two resolutions to be negligible. Resolution doesn't appear to affect input lag when image processing features are turned off (you should turn any of these off if you want the lowest possible input lag). We record lag times with the TV's game mode active because input lag is most important for gaming. We also note input lag in other picture modes for reference.