Web Tools
Regex Explainer
Parse regex patterns and get human-readable explanations for every token. Understands character classes, quantifiers, anchors, groups, lookaheads, backreferences, and flags. Visual color-coded breakdown of JavaScript regex syntax. Runs entirely in your browser — your data never leaves your machine.
regex regular-expression explainer parser javascript pattern reference
Published May 29, 2026
All interactive tools run entirely in your browser. Your data never leaves your device.
How It Works
Enter a regex pattern (with or without /flags) and get an instant token-by-token breakdown in plain English. Each token is color-coded by category: anchors, character classes, quantifiers, groups, lookarounds, backreferences, escape sequences, and flags. A summary line describes the overall pattern behavior.
Features
- Token-by-token parsing: breaks down every part of the regex with descriptions
- 10 token categories: anchor, character, class, quantifier, group, lookaround, backreference, alternation, escape, flag
- Color-coded output: each category has a distinct color for visual scanning
- Flag support: explains all JS flags (g, i, m, s, u, v, y, d)
- Lookarounds: positive/negative lookahead and lookbehind
- Named groups:
(?<name>...)with group numbering - Backreferences:
\1,\k<name>references - Pattern summary: auto-generated one-line description of the overall regex
- 5 examples: email, URL, US phone, password validation, IPv4 address
- Private: runs entirely in the browser — no data transmitted
Use Cases
- Understanding complex regex patterns written by others
- Learning regex syntax with instant visual feedback
- Debugging regex by seeing exactly what each token matches
- Documenting regex patterns with human-readable explanations