What Is Input Lag?
Input Lag (Input latency, System latency): The delay between an input — a click, keypress or mouse movement — and its result appearing on screen.
Definition
Input lag is the total time from a physical action — pressing a key, clicking, moving the mouse — until you see the result on screen. It’s measured in milliseconds.
Where Lag Comes From
Input lag is a chain, and every link adds time:
- Device: switch debounce and the polling rate of the mouse or keyboard.
- Computer: the operating system and the game process the input.
- Rendering: the GPU draws the next frame; low frame rates add delay.
- Display: the monitor waits for its next refresh, processes the image and changes the pixels.
How to Reduce It
- Use a high refresh rate monitor and keep FPS high.
- Turn on the monitor’s game or low-latency mode and disable heavy image processing on TVs.
- Use a 1000 Hz or faster mouse and keyboard, wired or with a good receiver.
- Turn off V-Sync or use variable refresh rate (G-Sync/FreeSync) instead.
The display and frame rate usually make the biggest difference; device polling rate is a smaller part of the total.
Measure It
- Monitor Refresh Rate TestFind out how many times per second your screen is really refreshing — and whether your high-refresh monitor is stuck at 60 Hz.
- Mouse Polling Rate TestMove your mouse and see how many times per second it reports to your computer — from 125 Hz office mice to 8000 Hz gaming sensors.
Related Guides
- 60Hz vs 144Hz vs 240Hz – Which Refresh Rate Do You Need?A higher refresh rate makes everything on screen look smoother. Here's how big the jumps really are, and what it takes to use them.
- Is 8000 Hz Polling Rate Worth It?Higher polling rates sound like a big upgrade. Here's what they really change — in milliseconds — and when they're worth turning on.
Related Terms
- Refresh RateHow many times per second a display draws a new image, measured in hertz (Hz).
- Polling RateHow many times per second an input device sends its state to the computer, measured in hertz (Hz).
- Response TimeHow long a display's pixels take to change from one colour to another, usually measured grey-to-grey (GtG) in milliseconds.
Part of the TapTest glossary · More in display tests.