Regex Visualizer
Visualize regular expressions as interactive railroad diagrams. Instantly understand complex patterns with a clear, readable SVG diagram.
Find this tool useful? Support the project to keep it free!
Buy me a coffeeWhat is Regex Visualizer?
The Regex Visualizer converts any regular expression into a railroad (syntax) diagram — a visual flowchart that shows how the engine reads your pattern step by step. Instead of parsing cryptic symbols, you see each component (literals, groups, quantifiers, alternations) laid out as a path through a diagram, making complex patterns immediately understandable.
How to Use Regex Visualizer
Common Use Cases
- Learning regex by visualizing what each token does
- Debugging complex patterns that behave unexpectedly
- Documenting regex patterns for teammates
- Teaching regular expressions in workshops or blog posts
- Verifying alternation branches and quantifier scope
Frequently Asked Questions
What regex syntax is supported?
The visualizer supports the JavaScript RegExp engine: character classes, quantifiers (*, +, ?, {n,m}), groups (capturing, non-capturing, lookahead, lookbehind), alternation (|), anchors (^, $, \b), and backreferences.
Is my regex sent to a server?
No. All parsing and diagram rendering happens entirely in your browser. Your patterns never leave your device.
What are railroad diagrams?
Railroad diagrams (also called syntax diagrams) show a grammar as a directed graph where the valid paths through the diagram represent valid strings. They were originally used to document programming language grammars.
Can I share my regex with the diagram?
Yes — the page URL auto-updates with your regex encoded in the hash, so you can copy and share the URL directly.