Regex Character Classes

Learn how a character class matches one character from a set, with a runnable example.

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Regular expression
Reference

Regex quick reference

^ · $
Start/end; m = lines.
[abc] · \d
Listed character / digit.
* · + · ?
Zero or more, one or more, optional.
(...)
Capture a numbered group.
(?<name>...)
Named capture.
(?=...)
Ahead; lookbehind varies.
i · m · s
Ignore case / line anchors / dot-newline.
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the RegExp of this browser (version not pinned)

Not available in JavaScript · This browser: x · ignore pattern whitespace; a · ASCII-only classes; U · lazy by default; J · duplicate names. u and v cannot be combined.

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Verified Fixture FX-S02

What it does

A character class matches exactly one character from a set, such as [A-F0-9] for one hexadecimal digit.

How to use it

  1. Load the example.
  2. Read the class in the Explanation tab.
  3. Check the counterexample.

Verified example

Example

Text "AF 09 GZ"

JavaScript · This browser
[A-F0-9]{2}

Result: "AF", "09"

Python re · Local WASM
[A-F0-9]{2}

Result: "AF", "09"

PCRE2-8 · Local WASM
[A-F0-9]{2}

Result: "AF", "09"

Go regexp · Local WASM
[A-F0-9]{2}

Result: "AF", "09"

Counterexample

Text "GZ"

JavaScript · This browser
[A-F0-9]{2}

Result: no match

Python re · Local WASM
[A-F0-9]{2}

Result: no match

PCRE2-8 · Local WASM
[A-F0-9]{2}

Result: no match

Go regexp · Local WASM
[A-F0-9]{2}

Result: no match

Recorded by running fixture FX-S02 on : rp.js@1 on Node v24.21.0 (V8), v24.21.0, CPython 3.14.2 (Pyodide 314.0.7), PCRE2 10.48, go1.27.1. JavaScript results come from the rp.js@1 core on Node’s V8; your browser runs the same core.

Engines

Limits