Regex Tester
Test JavaScript regular expressions against sample text, highlight matches and inspect capture groups locally.
🔒 Runs entirely in your browser — nothing is uploadedWhat Regex Tester does
Regex Tester runs a JavaScript regular expression against sample text, highlights every match, and lists capture groups for inspection. It is useful for validating log parsing patterns, form validation snippets, route matching, search-and-replace ideas, and small extraction tasks before the expression is copied into code. The tool always applies a global search so repeated matches are visible.
This page is designed for everyday developer work: quick checks while debugging, preparing small examples for documentation, and cleaning up data before pasting it into an editor, terminal, issue, or test fixture. The interface keeps the input, controls, output, and status message close together so the result is easy to verify before you copy it.
Private browser-based workflow
All processing happens with in-browser JavaScript. The tool does not upload your text, tokens, URLs, snippets, or generated values to a server, and it does not require an account. That privacy model is important because small utilities often receive real API responses, configuration samples, logs, authentication data, or customer-shaped examples during troubleshooting. Keeping the work local reduces risk and also makes the tool feel instant because there is no network round trip.
Practical tips
Enter the pattern without surrounding slashes and use the checkboxes for common flags. Zero-length matches are listed but not highlighted to avoid confusing output. Because browser RegExp behavior is the source of truth here, the result should match modern client-side JavaScript and current Node.js behavior for the same pattern and flags.
Always review transformed output before relying on it in production. Browser utilities are excellent for inspection and preparation, but they cannot understand every project convention or security requirement. If the result will be committed, shared publicly, or used in an authentication flow, double-check that it contains no secrets and that it matches the format expected by your application.
How to use
- Enter patternType a JavaScript regex pattern without slashes.
- Paste textAdd sample text to test.
- Review matchesInspect highlights, indexes, and capture groups.
Frequently asked questions
Should I include slashes?
Which engine is used?
RegExp engine.