We use the browser's native engine (ECMAScript), the same one running in Node.js, Deno and Bun. Syntax and supported flags follow the ECMAScript spec.
Regex Builder
Build, test and understand regular expressions in your browser.
Build and understand regex without leaving the browser.
This tool uses the browser's native RegExp engine. It validates the pattern as you type, highlights matches in the test text, lists captured groups and offers a structural breakdown of the pattern. The library covers common validations (email, URL, UUID, Brazilian phone, ISO date) with ready-to-go test samples.
Pattern, flags and test in one screen.
- Type or paste your regex in the main input — it is validated as you type.
- Toggle the flags you need (global, ignore case, multiline) with one click.
- Paste the text to test and see matches highlighted in the panel.