RegEx Tools
RegEx Tools
Test regular expressions against any input with live match highlighting; see capture groups, match indices, match count, and replacement output as you type. Visualize patterns as railroad diagrams, get token-by-token explanations, check for catastrophic-backtracking (ReDoS) risk, and browse a curated pattern library.
RegEx Tools
Test regular expressions against any input with live match highlighting; see capture groups, match indices, match count, and replacement output as you type. Visualize patterns as railroad diagrams, get token-by-token explanations, check for catastrophic-backtracking (ReDoS) risk, and browse a curated pattern library.
Common uses
- Test an email validation regex against sample input
- Extract all URLs from a text block
- Use named capture groups for date parsing
- Check a pattern for catastrophic-backtracking risk
Frequently asked questions
How do I test a regular expression?
Enter your pattern and flags, then type a test string. Matches and capture groups are highlighted live as you type.
Does it explain what a regex does?
Yes. The tool breaks a pattern down token by token and includes a searchable library of common ready-made patterns.
Is my data uploaded to a server?
No. This tool runs entirely in your browser — your input is processed locally on your device and is never uploaded or stored on a server.