Regex Tester
Test a regular expression against sample text with live match highlighting and flag support.
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Overview
Testing a regular expression by editing code and re-running it is slow. This tool highlights matches in real time as you adjust the pattern, flags, or test text.
- Live highlighting of every match in the test text
- Supports all standard JavaScript regex flags
- Clear error messages for invalid patterns
How to use it
- 1Enter your pattern and any flags
- 2Paste in sample text to test against
- 3Review the highlighted matches
Frequently asked questions
Which regex flavor does this use?
JavaScript's native RegExp engine — the same one used in browsers and Node.js. Behavior may differ slightly from other languages like Python or PCRE.
Why doesn't my pattern match anything?
Check that the flags are correct — for example, forgetting the 'i' flag means the match will be case-sensitive. An invalid pattern will show a specific error message instead of silently failing.