Check the connection and selected device, then repeat the failed check: the requested key is ignored.
Part of the Keyboard test. Run the full keyboard test first for a complete device check.
The requested key is ignored The sample varies sharply Reserved shortcuts interrupt the run
Keyboard latency test
Measure key-event-to-paint timing over a twenty-sample run with median and tail values.
Also known as: keyboard latency test, key latency test, keyboard input lag test, key delay test. Free, online, and no download required.
No permission neededNothing uploaded
Press the requested key when the target is ready.
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What the keyboard latency test checks
| Check | How it is measured | Fails when |
|---|---|---|
| Physical event | KeyboardEvent.code identifies the target press. | The requested physical position never arrives. |
| Paint opportunity | Two animation frames bound the next visible update. | The paint callback is interrupted or throttled. |
| Sample summary | p50, p95 and median absolute deviation summarize twenty values. | The run contains fewer than ten valid values. |
If something failed
Check the connection and selected device, then repeat the failed check: the sample varies sharply.
Check the connection and selected device, then repeat the failed check: reserved shortcuts interrupt the run.
02
How to read the result
How the keyboard latency test works
A valid keydown records the event timestamp, updates the target state and schedules two animation frames before storing the paint interval. Repeated keydown events are ignored. The sample list remains bounded to twenty entries and publishes through the shared harness rather than updating React from every browser callback.
What the result can establish
Use an ordinary key, keep the page focused and press once for each ready target. Do not use system-reserved combinations during the timing run.
Measurement limits
The value includes operating-system dispatch and browser rendering. It cannot isolate the keyboard scan matrix, USB transport or panel response.
03
Keyboard latency test questions
What is included in this keyboard input lag test result?
The value spans the keydown event timestamp to the next painted frame, so it contains operating-system dispatch, browser event handling and the full render path. It does not contain the keyboard scan matrix, USB transport or the display panel response.
Why do results change between runs of the same key test?
Frame timing, background tabs, power profiles and display refresh rate all shift the paint boundary. That is why the run reports a distribution over twenty samples instead of one number, and why a repeated median matters more than any single value.
Can I compare this key delay test with a camera measurement?
Not directly. A high-speed camera measures key press to visible light and includes hardware stages this page cannot observe. Use this test to compare two configurations on the same machine, not to validate a manufacturer's latency specification.