How to use Regex Tester
Enter a pattern, flags, and test text to see matches and capture groups. Start with a small known input, run the operation, and compare the result with the format expected by the system you are working with.
What this developer tool does
Test a JavaScript regular expression against text. It is intended for debugging, prototyping, inspection, and everyday development tasks where a quick local transformation is useful.
When this tool is useful
Use Regex Tester during debugging, prototyping, data inspection, test preparation, or small format conversions. It is designed for quick checks in the browser, while production systems should still rely on tested application code and the relevant technical specification.
How it works
The tool compiles the pattern with JavaScript regular-expression behavior and tests it against the provided text.
Practical example
For example, test a pattern on a small sample containing both matches and non-matches before using it in application code.
Developer notes
- Regular-expression syntax and features differ between programming languages and engines.
- Catastrophic backtracking can make some patterns very slow on adversarial input.
- A successful sample test does not prove a pattern handles every edge case.