Regex tester
Test regular expressions live, see if they work in JavaScript, Python, Go, Java, Rust and PHP, and get code for each.
DeveloperFreeRuns in your browser
The editor opens full screen. Your files stay in your browser.
Open regex tester- 01
Write a pattern, pick flags and paste some test text. Matches and groups highlight as you type.
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Read the plain-English explanation, and check for patterns that can hang a server.
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Open Languages to see what works where and copy ready-to-use code for your language.
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FAQ(4)
- Which regex engine does it use?
- Your browser's JavaScript engine runs the matches. Python, Go, Java, Rust and PHP are checked against their known differences, not run.
- Why does my regex work here but not in Go?
- Go's engine has no lookahead, lookbehind or backreferences. The Languages tab lists exactly which part of your pattern Go can't run.
- What is catastrophic backtracking?
- Some patterns take exponentially longer on certain inputs, enough to freeze a server. The tool flags those patterns and stops any test that runs longer than a second.
- Is my text sent anywhere?
- No. Everything runs in your browser.
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