Regex DoS (ReDoS) Checker
Check regular expressions for catastrophic backtracking that can freeze a server. Free and private: runs in your browser.
Paste one regex per line. Each is checked for nested quantifiers, overlapping alternations and slow matching on an adversarial string.
Runs entirely in your browser. Code, keys and tokens are never uploaded, logged or stored.
Use cases
- Spot-check a snippet during code review.
- Teach a team what the risky pattern looks like.
- Double-check a fix before you push it.
Frequently asked questions
What is ReDoS?
A regular-expression denial of service: a pattern like (a+)+ takes exponential time on certain inputs, so one request can block a thread for seconds or minutes.
Is the Regex DoS (ReDoS) Checker free?
Yes. It is free with no sign-up, and it runs entirely in your browser, so your input is never uploaded or stored.
Does a clean result mean my code is secure?
No. It means none of the common patterns this tool looks for were found in the snippet. Combine it with code review, dependency scanning and a full repository scan.
Related tools
Catch secrets, injection and unsafe code in every pull request with CodeInspector.