//
Test String
Loading editor…
177 characters • 3 lines Valid Pattern
Regex Tester (Offline & Secure)
Free online regex tester — write and test regular expressions in real-time with match highlighting, flag controls, and substitution preview. 100% client-side.
How to use Regex Tester
- Enter your regular expression pattern in the Regex field.
- Add any flags (e.g. g, i, m) in the Flags field.
- Paste your test text into the Test String panel.
- Matches are highlighted automatically, and the exact matches list is displayed.
Edge Cases & Important Considerations
- Invalid regex syntax will show a detailed syntax error.
- Catastrophic backtracking might cause browser lag with complex patterns on large strings.
Keyboard Shortcuts
- Ctrl/Cmd + K — Open Command Palette to switch tools instantly.
Frequently Asked Questions
Is this Regex Tester safe for sensitive corporate data?
Yes, 100%. All processing runs client-side in your local browser memory. No text, tokens, payloads, or logs are ever transmitted to any remote server or analytics engine.
Can I use this tool offline?
Yes. Because this tool runs strictly on client-side JavaScript with zero external API dependencies, once loaded it functions completely offline.
100% Client-Side Privacy Guarantee
All inputs are processed entirely inside your browser's memory using JavaScript. No data is ever transmitted to any server. Your tokens, JSON payloads, cURL commands, and timestamps never leave your machine.