About regular expressions
This is a regular-expression cheatsheet with a built-in live tester. Look up the syntax for anchors, character classes, quantifiers, groups and lookarounds, and test your own pattern against sample text with matches highlighted as you type. It uses the JavaScript regex engine and runs in your browser.
How Regex Cheatsheet works
How to use it
- Type a pattern and toggle the flags (g, i, m, s).
- Paste a test string to see matches highlighted.
- Use the reference cards below for the syntax.
How it works
Your pattern is compiled with the chosen flags and run over the test text; every match is highlighted and counted. The reference groups the most-used tokens so you can build patterns quickly.
Common uses
- Look up regex syntax
- Test a regular expression
- Debug a pattern
- Learn regex quickly
- Check what a pattern matches
- Build a validation regex
- Try flags and lookarounds
- Reference regex while coding
Frequently asked questions
Which regex flavour is this?
The JavaScript regex engine, used by browsers and Node.
How do I match all occurrences?
Enable the g (global) flag.
What does \b mean?
A word boundary.
Is my text uploaded?
No — everything runs in your browser.
What is a lookahead?
A check for what follows without consuming it, like (?=...).
How do I match case-insensitively?
Turn on the i flag.
Is it free?
Yes — completely free with no sign-up.