Regex Tester
Test Regular Expressions
Test JavaScript regular expressions with timeout protection, highlighted matches, groups and transformation previews.
Unsupported flags are disabled automatically. JavaScript does not allow u and v together.
Regex Result
Highlighted Matches
Match Details
Replace Preview
Split Preview
JavaScript Snippet
Export Results
Plain-text export contains the matched values. JSON export also includes positions, groups, named groups, indices and timing.
About
The XAVERT Regex Tester evaluates patterns with the browser's native JavaScript RegExp engine.
Main Features
- Test JavaScript-compatible regular expressions against custom text.
- Use g, i, m, s, u, y, v and d flags when supported by the browser.
- Run regex evaluation inside a disposable Web Worker so expensive patterns can be terminated without freezing the page.
- Choose an execution timeout from 250 ms to 2 seconds.
- Highlight matches and inspect their start and end positions.
- Inspect numbered capture groups and named capture groups.
- Inspect match indices when the d flag is enabled and supported.
- Preview JavaScript replacement and split results.
- Review heuristic warnings for common nested-quantifier and ambiguous backtracking patterns.
- Use quick presets for numbers, words, URLs, email and ISO dates.
- Generate a ready-to-use JavaScript RegExp snippet.
- Copy or download plain matches and structured JSON results.
Privacy First
Pattern evaluation, test text, replacement previews and exported data are processed locally in your browser. This tool does not require a third-party runtime and does not upload your regex content to XAVERT.
This tool uses JavaScript regular-expression syntax. PCRE, .NET, Python and other regex engines can support different features or semantics. Backtracking risk detection is heuristic; the execution timeout remains the final protection against an expensive pattern.