See how many keys your keyboard registers at once, test gaming combos and find the apparent limit.
Rollover is the number of keys a keyboard can report at the same time without dropping any. In games and multi-key shortcuts (moving diagonally, jumping and sprinting, Ctrl + Shift + Alt + key) a low limit makes commands get ignored. This tool lights each key while it is held, shows the peak of simultaneous keys and checks whether combos such as WASD + Space all arrived together. The test runs in the browser only and nothing you type is sent anywhere.
Paste the code into your HTML and the tool shows up on your page, without J-Kit's navigation and ads. It still runs in the browser of whoever visits your site.
<iframe
src="https://jkit.tools/embed/en-US/keyboard-rollover-test"
width="100%"
height="600"
style="border:0"
loading="lazy"
title="Keyboard Rollover Test (N-Key)"
></iframe>These references help contextualize formulas, standards, APIs and limitations used on this page. They do not replace professional validation when a result has legal, financial, medical or operational impact.
Rollover is a keyboard's ability to report several pressed keys at once. N-key rollover (NKRO) means any number of keys is registered independently. 6KRO means up to six regular keys (plus the modifier keys) are reported together.
The browser only sees what the operating system hands it. If a key goes missing it may be a hardware rollover limit or ghosting in the keyboard matrix, and software cannot tell the two apart. The "apparent limit" is just the most keys that arrived together.