Regex Character Class Builder ([abc], [a-z], [^...])

Character classes ([abc], [a-z], [^xyz]) are the most flexible regex feature and the easiest to get wrong (especially escaping). This builder lets you check boxes — digits, letters, specific chars, ranges — and outputs the correct character class syntax.

How to use the Regex Character Class Builder ([abc], [a-z], [^...])

Toggle the common classes, add custom chars or ranges, and the regex output updates live. Optional negation wraps the class with ^.

What a character class actually matches

A character class, written with square brackets, matches exactly one character from the set inside it. [aeiou] matches any single vowel, [a-z] uses a range, and [^0-9] negates — matching any one character that is not a digit. Ranges follow code-point order, which is why [A-Za-z] needs two of them: uppercase and lowercase letters are not adjacent in ASCII.

Inside a class the usual rules change. Metacharacters like ., *, and ( become literal, so you almost never escape them here. The few characters that stay special are ], the backslash, ^ (only in first position), and - (only between two characters). To include them literally you put - first or last, or ] first — exactly the placement this builder works out for you.

Common use cases

• Slug and username rules — define precisely which characters an identifier may contain.
• Password policies — build the "at least one of these" sets a strength check needs.
• Input sanitising — strip everything outside an allow-list with a negated class.
• Targeting Unicode ranges — match a specific script or block by code-point range.
• Learning the escaping rules — see why a hyphen or bracket does or does not need a backslash.