Private by design: regex matching runs in your browser and is not uploaded to ShishwaLab servers.
Enter a pattern and test string.
Matches0
Highlighted matches
Match list
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Regex Tester
Test regular expressions with flags, match highlighting, capture groups, and optional replace—all locally. Free, fast, and built for a clean browser workflow.
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About this tool
The ShishwaLab Regex Tester lets you try JavaScript regular expressions against sample text with match highlighting and capture-group details.
Optional replace uses the same pattern so you can preview substitutions before shipping code. Invalid patterns show a clear error instead of crashing the page.
Testing runs locally. Your patterns and strings are not uploaded to ShishwaLab servers.
Tips for better results
- Prefer the g flag when you want every match; without it the tool still scans globally for listing.
- Watch empty-match loops—patterns like x* can match zero-length positions; the tester advances safely.
- Very large inputs are capped and match lists are limited to keep the tab responsive.
- Escape user text carefully when building patterns dynamically in your own apps.
How to use
- 1 Enter a pattern and flags (for example gi).
- 2 Paste a test string, optionally add a replacement, then click Test.
- 3 Review highlighted matches, group details, and the replaced output.
FAQ
Is this regex tester free?
Yes. Test patterns and replacements in your browser at no cost.
Which regex flavor is used?
JavaScript RegExp, including flags such as g, i, m, s, u, and y when supported.
Is my text uploaded?
No. Matching runs locally and is not uploaded to ShishwaLab servers.
Can I replace matches?
Yes. Provide a replacement string to preview substituted output.
Are capture groups shown?
Yes. Listed matches include indexed groups when present.
What about invalid patterns?
You get an error message and no false match list.