Input Lag Test

What Is Input Lag?

Input lag is the delay between a physical action, such as clicking or pressing a key, and seeing the result on screen. It builds up along a chain:

1. Device: switch debounce and polling rate in your mouse, keyboard or controller.
2. Computer: the operating system delivers the input and the app or game processes it.
3. Rendering: the next frame is drawn, which waits for the frame timer.
4. Display: the monitor receives the frame, processes it and changes its pixels.

Total lag on a good gaming setup can be under 20 ms. On a TV with heavy picture processing it can exceed 100 ms.

What This Input Lag Test Measures

A web page can't see your monitor's pixels change, so no browser test can measure true end-to-end, click-to-photon lag. Instead this page gives two honest measurements:

• Input-to-frame delay: the time from the moment your input reached the browser to the start of the next frame that shows the response. This covers the browser and computer part of the chain.
• Reaction time: how long you take to click after the screen turns green. This includes your own reaction plus every part of your setup's lag, so it's a useful real-world comparison between setups.

The tool also measures your display's refresh rate from the frame timing and adds one frame to give a rough "on screen" estimate. Your monitor's own processing and pixel response come on top of that.

How to Run the Test

1. Close other heavy tabs and apps so the computer isn't busy.
2. Input-to-frame: click or tap the first panel about 20 times at a steady pace. To test a keyboard, click the panel once, then press any key repeatedly.
3. Reaction time: click the second panel to start. Wait for red to turn green, then click as fast as you can. Clicking early restarts the round. After five rounds you get your average.
4. Compare setups: try a different mouse, a wired connection, or another monitor and see how your numbers change.

Reading Your Results

If the refresh rate reads 60 Hz on a high refresh rate monitor, check Windows Display settings > Advanced display, or macOS Displays settings, and choose the highest refresh rate. A 144 Hz monitor running at 60 Hz adds lag to everything you do.

Monitor Input Lag

Monitor input lag is the time a display takes to show a frame after receiving it. Gaming monitors usually add only a few milliseconds. Office monitors and TVs can add much more, because they process the image before showing it. Pixel response time, how quickly pixels change colour, is a separate figure that affects motion blur more than lag.

To measure a monitor's own lag you need a high-speed camera filming the screen next to a reference display, or a dedicated lag tester device. Independent monitor reviews publish these measurements, which is the best way to compare models.

Keyboard and Controller Input Lag

Keyboards and controllers add lag through switch debounce, polling rate and their connection. A 125 Hz keyboard adds up to 8 ms just waiting to report; a 1000 Hz one adds up to 1 ms. Bluetooth controllers usually add more delay than wired or dongle connections.

Check the device side with the Keyboard Polling Rate Test and the Controller Polling Rate Test, then use the reaction test here to compare devices on the same screen.

TV Game Mode and Lag

TVs apply motion smoothing, noise reduction and sharpening by default, and each step adds delay. Game Mode, often switched on automatically with ALLM (Auto Low Latency Mode) on newer TVs and consoles, turns most of it off. If games feel sluggish on a TV, turn on Game Mode, use the HDMI input marked for gaming, and run the reaction test before and after to feel the difference.

How to Reduce Input Lag on PC

• Use your monitor's full refresh rate and connect with DisplayPort or a high-bandwidth HDMI cable.
• Raise your frame rate: lower graphics settings in games so frames are drawn sooner.
• Be careful with V-Sync: it removes tearing but can add a frame or more of delay. Variable refresh rate (G-Sync or FreeSync) with a frame cap just below your refresh rate is a good middle ground.
• Use 1000 Hz wired or dongle devices rather than Bluetooth for your mouse and keyboard.
• Close background apps that use a lot of CPU or GPU, such as video encoders or many browser tabs.
• Turn off battery saver on laptops, which can lower refresh rate and slow input handling.

Why Browser Delay Varies

Your input-to-frame delay depends on where in the frame your input lands. An input that arrives just before a new frame starts shows up almost instantly; one that arrives just after must wait almost a full frame. That's why the results vary between samples, and why the average and best values together tell you more than any single reading. A busy page or computer can also make the browser miss a frame, which shows up as an occasional much higher sample.

Using Reaction Time to Compare Setups

Your reaction time is mostly you, about 150 to 250 ms of it, but the last 10 to 100 ms comes from your setup. To compare two monitors, mice or TV modes, run five rounds on each in the same session, with the same hand and posture, and compare the averages. A difference of 20 ms or more between setups is usually real; smaller differences can be normal variation in your own reactions.

Limitations

This test can't see your monitor's processing or pixel response time, and it can't see delay inside your mouse or keyboard before the operating system receives the input. Event timestamps are slightly coarsened by browsers for privacy. Reaction time varies with attention and fatigue, so compare averages over several rounds rather than single results.

Related Tests

• Mouse Polling Rate Test: check your mouse reports at 1000 Hz.
• Controller Polling Rate Test: measure your gamepad's update rate.
• Touch Sampling Rate Test: the touchscreen side of input lag.