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Regex Tester
Test and debug JavaScript regular expressions with live matches, highlighting, and quick feedback to refine patterns for validation, search, and replace.
How to use this tool
- Enter a regex pattern and toggle the JavaScript flags you want to test.
- Paste sample text to preview highlighted matches and indexed match output.
- Copy or download the test summary for debugging notes or team review.
Developer workflows
- Validate form patterns before shipping client-side or server-side checks.
- Prototype search expressions for editors, scripts, and migration tasks.
- Compare match behavior quickly when toggling global, multiline, or unicode modes.
Troubleshooting notes
- Syntax errors are shown instantly so invalid patterns are easy to spot.
- Patterns run with the browser’s JavaScript RegExp engine (ECMAScript behavior).
- Use representative multiline samples to confirm anchor and dot behavior.
FAQ
- Which regex flavor does this tool use?
- It uses JavaScript RegExp in the browser, so behavior follows ECMAScript rules.
- Can I test multiline text?
- Yes. Paste multiline input and enable the multiline (m) flag when needed.
- Does this tool support replacement previews?
- No. This tool focuses on pattern matching, highlighting, and match index inspection.
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