When this tool is useful
A regex tester is useful when checking a pattern, debugging flags or extracting repeated values from a text sample. Test it on representative examples before using it on production data.
How to use it
- Enter a regular-expression pattern and a representative test string.
- Choose supported flags and run the match check.
- Review matched text and positions, then test edge cases before using the pattern in code.
Common uses
- Debugging a regular expression
- Extracting a repeated pattern from text
- Checking matching behaviour before applying a pattern to real data
Tips for a reliable result
Tips for a reliable result
Test the pattern against both matching and non-matching examples before using it in an application. Regular-expression features and flags can differ between programming languages.
Frequently asked questions
Can it extract matching text?
Yes. Enter a pattern and sample text; matching strings and their indexes are shown, along with capture groups when present.
What do regex flags do?
Flags such as g, i, m and s alter how the expression matches text. Use only flags supported by the target JavaScript environment.
Why does my pattern fail?
A malformed expression or unsupported flag can cause an error. Simplify the pattern and test a small example before expanding it.
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