Regex Visualizer

Seeing the structure of a pattern

Reading someone else's regular expression is a different skill from writing your own — you're parsing a dense string of punctuation back into the structure it represents. This tool does that parsing for you: paste a pattern and it's broken down into nested boxes for groups and alternatives, with a badge on anything that repeats, plus a plain-English line-by-line breakdown underneath. Hover any piece of the diagram for its description.

It runs entirely client-side against a small hand-written parser covering the constructs you'll meet in practice — literals, character classes, anchors, quantifiers, groups (capturing, non-capturing, named, and lookaround), alternation, and backreferences.

Reading the diagram

• Gray pills are literal text, character classes, anchors, or backreferences.
• Blue boxes are groups — capturing, non-capturing, named, or a lookahead/lookbehind — labeled with what kind they are.
• Amber boxes are alternation: exactly one of the branches inside must match.
• A violet badge attached to a piece shows its quantifier, e.g. 1+ for one or more, 0-1 for optional, or 2-4 for a bounded range.

FAQ

Why does my pattern show an error here but seems to work elsewhere?

This tool validates with the same RegExp engine your browser uses, so a pattern that's invalid here is invalid in JavaScript. If it worked in another language (PCRE, Python's re, POSIX), the syntax may differ slightly — JavaScript regex isn't 100% identical to every other flavor.

Does this tool test my pattern against text?

No — it only visualizes structure. To test a pattern against sample text with match highlighting, use the Regex Tester. To build a pattern from scratch by clicking pieces together instead of writing it by hand, use the Regex Builder. To step through exactly how a match attempt unfolds — including catching catastrophic backtracking — use the Regex Debugger.

New to regex syntax entirely?

The Regex for Beginners guide walks through the same building blocks this tool visualizes — character classes, anchors, quantifiers, and groups — from scratch. Want a token reference to keep handy while you work? The Regex Cheat Sheet Generator exports a customizable syntax reference as Markdown or plain text.