Regex Tester

About the Regex Tester

This regex tester uses the same ECMAScript RegExp engine that runs in your application, so what matches here matches in production. Toggle the global, case-insensitive, multiline, dotAll, and unicode flags and watch matches highlight as you type. Capture groups are listed individually for each match so you can see what your patterns actually pull out. Because this tester uses the native engine, it supports lookaheads, lookbehinds, named capture groups, and Unicode property escapes — features that PCRE-based testers handle differently.

Common use cases

• Validate email, URL, and phone patterns before deploying form validation
• Build extraction patterns for log parsing and ETL pipelines
• Debug a regex that works in your editor but fails in production JS
• Check capture group indices when migrating to named groups
• Verify Unicode-aware patterns with the u flag

Why client-side?

Every byte you paste, type, or upload here is processed entirely inside your browser. Nothing is sent to a server, logged, or stored. That means it's safe to use this tool on production secrets, customer data, internal logs, and any input you would not paste into a hosted SaaS formatter.