Regex Tools
Free online regular expression tools — test, explain, build replacements and reference a cheatsheet. Prototype patterns and verify backreference behavior entirely in your browser.
4 free regex tools — all browser-based
Regex Tester
Tests regular expressions against sample text in real time, with configurable flags, highlighted matches, capture groups, and match index details..
Regex Explainer
Breaks a JavaScript regular expression into its tokens and explains each one in plain language (anchors, groups, quantifiers, character classes, lookarounds, flags), showing the capture-group structure and matching flow.
Regex Replacement Tester
Tests JavaScript regular expression substitutions interactively, applying a replacement string with capture-group references ($1, $2, named groups) and function replacements to a sample text, with a live before / after diff and match highlighting, useful for prototyping sed-like transforms, building search-and-replace rules, and verifying backreference behavior across engines..
Regex Cheat Sheet
A searchable reference of common regular expression syntax.
Testing and explaining regular expressions
The Regex Tester matches your pattern against sample text and shows capture groups and match positions.
Use the Regex Explainer to get a plain-English breakdown of what each token in your pattern does.
Building regex replacements
The Regex Replacement Tester applies substitutions with $1 backreferences and named groups, plus case tokens, and shows a before/after diff.
Frequently asked questions
Which regex flavor do these tools use?
They use the JavaScript (ECMAScript) regular expression engine, the same one that runs in your browser and Node.js.