Regex Tester
Test a regular expression pattern against sample text. Review matches, captured groups, and pattern errors.
JavaScript regular expression syntax is used. Duplicate flags or invalid patterns will show an error.
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Privacy: regex evaluation runs locally in your browser. No pattern or text is stored or transmitted.
How it works
Enter a JavaScript regex pattern and optional flags, then test it against input text. In replace mode, the tool also applies a replacement string.
Examples
- \b\w4\b with g finds 4-letter words
- \d+ with g finds all number sequences
- (cat|dog) with i matches either word case-insensitively
When to use this tool
This tool is designed for quick, practical tasks such as everyday calculations, data formatting, or simple conversions. It is best used when you need fast results without installing software or using complex tools.
When to use
- Quick checks or one-time calculations
- Validating or converting data before using it elsewhere
- Simple tasks that do not require advanced software
When not to use
- Critical financial, legal, or medical decisions
- Large-scale or automated processing
- Situations requiring guaranteed precision beyond basic validation
Always review results before using them in important contexts.
About this tool
This tool helps you perform quick utility operations directly in your browser. It runs entirely in your browser without sending data to a server.
You can use this tool when handling simple tasks without installing additional software. The results should be interpreted as a processed output based on your input data.
FAQ
- What does this regex tester do?
It tests a regular expression pattern against input text and shows matches, groups, flags, and errors.
- Which flags are supported?
Common JavaScript regex flags are supported, including g, i, m, s, u, and y.
- What happens if the pattern is invalid?
The tool shows a validation error and does not attempt matching until the pattern is corrected.
- Are my patterns or test strings stored?
No. Everything runs locally in your browser and is not stored or transmitted.