Tool
Check Regex and Pattern with Regex Tester and use the result to find common errors before the next development or publishing step.
Regex Tester
Check Regex and Pattern with Regex Tester and use the result to find common errors before the next development or publishing step.
Live Tool
Regex Tester
Check Regex and Pattern with Regex Tester and use the result to find common errors before the next development or publishing step.
Tool Workspace
Regex Tester
Check Regex and Pattern with Regex Tester and use the result to find common errors before the next development or publishing step.
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Regex Tester
Check Regex and Pattern with Regex Tester and use the result to find common errors before the next development or publishing step.
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Check Regex and Pattern with Regex Tester and use the result to find common errors before the next development or publishing step.
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About Regex Tester
Regex Tester lets you test a regular expression against sample text, inspect matches and capture groups, and refine a pattern before you add it to code, validation, or a data-cleanup workflow.
Reference: MDN guide to regular expressions
01
How to use it
- Enter a representative sample, including edge cases that should and should not match.
- Build or paste the pattern, choose flags deliberately, and inspect whole matches plus numbered or named groups.
- Repeat the test in the destination language or runtime because regex syntax and flag behavior can differ between engines.
02
Frequently asked questions
Why does a regex work here but not in my application?
Regex engines differ in supported syntax, Unicode handling, backtracking limits, and flags. Test the final pattern in the same language and version used by your application.
What are capture groups for?
Groups let you extract or reference a portion of a match. Use non-capturing groups when you only need grouping, not a captured value.
Can a regex create a security or performance issue?
Yes. Some patterns can backtrack excessively on adversarial input. Put length limits and timeouts around untrusted input, and review complex patterns before production use.
03
Input, output, and validation
Paste or enter technical content, run the tool, and use the output to support debugging, formatting, or data exchange. For structured data, also verify syntax, field types, encoding, and the destination system's constraints.
Example check: start with a minimal sample that contains no keys, tokens, or production data. Verify the structure and result, then apply the same rule to a working copy.