Regular Expression (Regex) Tester
Regular Expression (Regex) Tester
Test a JavaScript regular expression against text with case and multiline options.
Tip
Test a regular expression against representative data before using it to filter or modify production data.
Use the result with confidence
Recommended workflow
- Use a non-sensitive representative input for testing a regular expression.
- Run the operation and review the result before copying or exporting it.
- Validate the output in the target application or environment before relying on it.
What to verify
- Confirm the scope, units and input values before interpreting the output.
- Separate the observed result from the operational decision that follows from it.
- Validate the conclusion against the real target system, logs or configuration before changing production.
Questions about this tool
Why can the same regular expression behave differently elsewhere?
Regex engines differ in supported syntax, flags, Unicode handling and backtracking behaviour. Test against the engine used in production.
Can a regex cause performance problems?
Yes. Nested or ambiguous quantifiers can cause catastrophic backtracking on some engines and inputs.
What test set should I use?
Include expected matches, expected non-matches, empty or malformed values, Unicode if relevant and boundary-length inputs.
Use the result with confidence
Recommended workflow
- Use a non-sensitive representative input for testing a regular expression.
- Run the operation and review the result before copying or exporting it.
- Validate the output in the target application or environment before relying on it.
What to verify
- Confirm the scope, units and input values before interpreting the output.
- Separate the observed result from the operational decision that follows from it.
- Validate the conclusion against the real target system, logs or configuration before changing production.
Questions about this tool
Why can the same regular expression behave differently elsewhere?
Regex engines differ in supported syntax, flags, Unicode handling and backtracking behaviour. Test against the engine used in production.
Can a regex cause performance problems?
Yes. Nested or ambiguous quantifiers can cause catastrophic backtracking on some engines and inputs.
What test set should I use?
Include expected matches, expected non-matches, empty or malformed values, Unicode if relevant and boundary-length inputs.