Regex Tester Online — Free · Real-time · No Signup
Real-time · 26 features · AI explain · Unit tests · Diff mode · JS/Python/PHP · 100% browser
Free online regex tester — no account needed, no data uploaded. Test patterns in real-time with live highlighting. Works offline. 26 features including unit tests, replace mode, diff, AI explanation, and code snippets.
What is a Regular Expression?
A regular expression (regex) is a sequence of characters that defines a search pattern. Used for validation, parsing, text manipulation, and data extraction in virtually every programming language — JavaScript, Python, PHP, Java, and more.
How to Use This Regex Tester
Type your regex pattern in the input field. Matches highlight in real-time in the test text panel. Use the flags (g/i/m/s/u/y) to modify matching behavior. Switch between Test, Replace, Unit Test, Diff, and Multi-string modes using the tabs above.
Frequently Asked Questions
Is this regex tester free?
Yes, completely free. No account, no signup, no rate limits. All processing happens in your browser using JavaScript's built-in RegExp engine.
Does this tool work offline?
Yes, after the page loads, the regex engine works completely offline. Only the AI explanation feature requires an internet connection.
Can I save my regex patterns?
Yes, use the Presets feature to save up to 10 regex configurations (pattern + flags + test text). They're saved in your browser's localStorage and persist between sessions.