HTML · Form and input attributes

pattern

A regular expression the field value must match. Always pair it with a visible hint.

htmlRunnable example html course

Syntax

pattern="[A-Za-z]+"

Example

Try it

<input pattern="[0-9]{4}" placeholder="4 digits" aria-label="PIN">

Reference pages are the quick answer. The course explains the why, shows the full example and ends with a challenge.