CodeASystem developer tools
Test & debug regex, in real time.
Verify regular expression patterns, inspect nested capture groups, test multi-line text, and preview replacements locally.
Regex Tester & Explainer
Build, test, and debug regular expressions with live match highlighting and capture group inspection.
Quick Presets:
//
Test String
Matches (2)
Match #1Index 8..31 (23 chars)
Match #2Index 35..65 (30 chars)
Processing happens entirely inside your browser. No strings or expressions are transmitted to any server.
How it works
Native browser RegExp engine. Zero telemetry.
Patterns and test strings are evaluated strictly by your local JavaScript runtime. Complex expressions and confidential test payloads remain completely private.