HTMLRegex Tester
Test regular expressions live, inspect match ranges and capture groups, then export a copyable regex fixture pack with expected match counts, ranges, and starter Node test code. Supports JavaScript regex flags g, i, m, and s. Everything runs in your browser.
Ctrl+Enter to run | Ctrl+K to switch tools | Recent button shows input history
Repeating this work? Turn this kind of browser utility into an API batch, MCP prompt, extension workflow, or shared team recipe.
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Which regex engine is used?
JavaScript's built-in RegExp engine (ECMAScript standard). Supports lookaheads, backreferences, named groups, and Unicode properties.
What is in the regex fixture pack?
The pack includes the reviewed pattern, flags, expected match count, match ranges, capture-group counts, setup notes, and a starter Node test. It intentionally omits raw matched values so you can add a reviewed fixture.txt in your own project.
Why am I getting no matches?
Common causes: missing i flag for case-insensitive matching, anchors ^ and $ not matching as expected without the m flag, or special characters not escaped (use \d not d, \. not .).