Online Regex Tester, Debugger & Substitution Tool
Evaluate regular expressions with synchronized match highlighting, named capture group inspection, real-time string substitution, and comprehensive pattern presets. Runs 100% inside your browser via dedicated Web Workers to ensure proprietary logs and sensitive payloads never leave your device.
#How to Use This Tool
#Mathematical Formula & Standards
#Edge Cases & Technical Considerations
Zero-Length Matches & Anchors (^, $, \b)
Handled with automated index stepping to prevent infinite evaluation loops while accurately highlighting word boundaries and line anchors.
Named Capture Groups & Unicode Code Points
Full support for ES2018+ named capture groups (?<name>...) and Unicode (u flag) character classes, preserving multibyte glyphs and astral symbols.
Catastrophic Backtracking Mitigation
Executes safely inside an isolated background Web Worker with match count safeguards (capped at 5,000 matches) to prevent UI thread freezing.
#Frequently Asked Questions
Q:Are my logs or sensitive strings uploaded to any remote server?
No. The regex engine runs entirely in your browser using an isolated Web Worker. Zero bytes of your pattern or test string are transmitted over the network.
Q:Which regular expression dialect is supported?
The engine uses standard modern JavaScript (ECMAScript) RegExp, including support for named capture groups, lookaheads, lookbehinds, and Unicode property escapes.
Have feedback or feature requests?
Help us improve this utility. Share suggestions, report edge cases, or request new features directly.
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