Input Lag Test
Time the full path from a button press to the pixels changing: mouse, computer and display together. Use a phone slow-motion flash test, compare two screens with a stopwatch, or see the delay inside the browser. This is not a reflex test, and it cannot separate the monitor on its own.
- Set your phone to slow motion at 240 fps (or the highest it offers) and frame both the mouse button and this pad.
- Start recording, then click the pad a few times, a second or two apart. Full screen gives a bigger flash.
- Step through the video frame by frame. Count the frames from the first frame where the button is fully down to the first frame where the pad turns white.
- Enter that count below. At 240 fps each frame is 4.17 ms. Average at least five presses.
A web page cannot time the light leaving your screen, so no browser test can measure display lag on its own. The camera method measures the whole chain from the button to the pixels, including the mouse and the computer, not the panel alone and not your reflexes. The browser estimate shows only the part inside the browser.
Slow-motion frame calculator
Converts the frame count you enter. Includes the mouse, the computer and the display. Does not include reaction time, and it is not the monitor on its own. Once a count is entered, the ± figure is one video frame.
Does the 1 ms on the box mean 1 ms of lag?
What input lag is made of
Input lag is the time from pressing a button to seeing the result. It stacks up from the mouse or controller (1 ms at a 1000 Hz polling rate, 8 ms at 125 Hz), the OS, the game or browser rendering a frame, the display processing the signal, and finally the pixels changing colour. The camera method catches all of it at once, which is why it is called click-to-photon latency. It does not include how long you take to react, and the monitor stays mixed into that total.
Typical numbers
Good gaming monitors add under 5 ms of their own processing, and a full click-to-photon chain on a 240 Hz setup is often 10 to 20 ms. A 60 Hz office screen plus a browser usually lands around 30 to 50 ms. TVs are the big swing: in game mode many sit near 10 to 20 ms, but with picture processing on they reach 50 to 100 ms or more. Inside the browser expect one to two frames, about 7 to 14 ms at 144 Hz. Check the rate with the refresh rate test.
How to cut it
On a TV, turn on Game mode or ALLM and switch off motion smoothing, noise reduction and similar picture processing. Run the highest refresh rate your screen supports, since every frame you wait for gets shorter. Use a wired mouse or a 2.4 GHz dongle rather than Bluetooth, and set it to 1000 Hz polling. In games, an uncapped or slightly capped frame rate and low-latency modes help; V-Sync usually adds a frame or more.
The 1 ms on the box
The "1 ms" printed on most gaming monitors is pixel response time, how fast a pixel changes from one grey to another, usually measured at the most aggressive overdrive setting. It says nothing about how long the monitor holds a frame before showing it. A screen can claim 1 ms and still add 15 ms of processing. Smearing from slow pixels shows up in the ghosting test. Processing delay only shows up inside a camera click-to-photon total, not as a monitor-only reading.
Related tools
Time your own reflexes, which this page leaves out, with the reaction time test, confirm your screen's real rate with the refresh rate test, check your mouse with the mouse polling rate test and look for motion blur with the monitor ghosting test.
Frequently asked questions
What does this page measure?
Three different things, and none of them is your reaction time. The slow-motion camera method times the whole click-to-photon chain, from the button going down to the pad turning white. That total includes the mouse or keyboard, the operating system, the browser, display processing and the pixels changing. It is not the monitor on its own. The stopwatch only shows which of two mirrored screens is behind. The browser estimate only times from the click or key event to a later animation frame inside the page.
Why is the camera result not pure display lag?
The frame count starts at the physical press, and a web page cannot see the light leaving the panel. Mouse debounce, the USB or radio hop, the operating system and the browser sit in the same count as the monitor. Nothing here subtracts a human reaction time, because you are not reacting to a signal. To compare two displays, mirror them and use the stopwatch on the same computer.
How does the slow-motion count work?
Film the button and this pad together. Step from the first frame where the button is fully down to the first frame where the pad is white, then multiply that count by 1000 divided by the video frame rate, or use the calculator. At 240 fps one frame is 4.17 ms, and that is the uncertainty on a single count. Average several presses. If the button or the pad is out of frame, or the phone drops frames, the count is wrong. The on-screen clock starts when this mode opens and stamps each press. It is not a lag reading, and it does not start on a stimulus.
What does the two-screen stopwatch show?
The same counter is mirrored onto two screens and you photograph both. The gap between the readings is how far one display trails the other. It is not an absolute lag figure and it does not include your reflexes. The counter changes only once per refresh, so one photo is only good to about one frame (16.7 ms at 60 Hz). Skip shots where the digits are blurred or doubled, and take the median of several photos. The clock runs from when you open this mode or press Run. It is a source to photograph, not a reaction timer.
What is included in the browser number?
The large figure is the median time from the click or key event to the animation frame after the colour change is drawn, about when that frame is handed to the screen. To next frame is the earlier step. The number leaves out mouse hardware and operating system time before the event, and monitor processing and pixel response after it. It is not your reaction time. An empty run shows dashes, not zero. The clock starts at the event, not at a colour cue, so an early press is not scored as a tiny lag. A held key does not add extra samples, and the later click event is not counted again. Recording stops at 20 presses.
Does the 1 ms on the box match this test?
No. That figure is usually pixel response time: how fast a pixel changes shade, often at the strongest overdrive setting. A panel can print 1 ms and still hold a frame much longer before showing it. Smear from slow pixels is a different problem, and it is what the ghosting test looks for. This page does not turn the box number into a measured lag.