What Is N-Key Rollover?

Rollover describes how many simultaneous key presses a keyboard is designed to report correctly. N-key rollover, or NKRO, is the common marketing term for a board designed to report every key independently.

The matrix problem

Many keyboards share electrical rows and columns between keys. Certain three key combinations can confuse the matrix, causing a key to appear pressed when it is not, which is ghosting, or causing a key to drop out.

What NKRO means

An NKRO keyboard is designed so that every key reports independently over USB, usually with a larger report size. A 6-key rollover board, often labeled 6KRO, is designed to handle at least six simultaneous keys.

What a browser can see

The N-key rollover test shows how many key events the operating system delivers to the page. That is useful evidence, but USB polling, firmware, OS shortcuts, and focus can all change the result. A browser test cannot certify hardware.