Free Regex Tester (JavaScript)
Write a pattern, paste test text, and see matches highlighted live · with capture groups, flags, and match positions.
Frequently asked
Which regex flavor is this?
JavaScript (ECMAScript) · the flavor your frontend and Node.js code actually run. Most patterns port from PCRE, but lookbehind support and some escapes differ, so testing in the target flavor matters.
What is catastrophic backtracking (ReDoS)?
Patterns with nested quantifiers like (a+)+ can take exponential time on crafted input · a denial-of-service vector if the pattern runs server-side on user input. Prefer specific character classes over nested .* quantifiers.
Related tools
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- Semver Checker · Enter a version range like ^4.2.0 and a version to test · see whether it matches and what the range actually allows.
- URL Parser · Paste any URL and see every part broken out · protocol, host, path, and each query parameter decoded into a readable table.