Regular expression (regex) tester
Test your regular expressions directly in your browser: no data is sent to a server. Enter a pattern and a text, and matches are highlighted and listed live with their position and captured groups.
Important limitation: this tester uses the Rust regex engine, guaranteed to run in linear time, which doesn't support certain PCRE features such as backreferences (\1) or lookaheads/lookbehinds ((?=...), (?<=...)). A pattern that works in JavaScript may therefore fail to compile here.
How it works
Are you writing a regular expression to validate an email or phone field in a form, or to extract data (identifiers, dates, amounts) from plain text? Paste your pattern and a sample text: matches are highlighted live as you type, with their position and captured groups, so you can immediately check whether your regex behaves as expected.
Why doesn't my regex with a lookahead (?=...) work?
This tester uses the Rust regex engine, chosen to guarantee linear execution time even on long text. This engine doesn't support lookaheads/lookbehinds ((?=...), (?<=...)) or backreferences (\1), unlike JavaScript's regex engine. A pattern that works in your browser or in another tool may therefore fail to compile here. There is generally an alternative without lookahead: for example, splitting the processing into several steps or rephrasing the condition directly in the pattern.
How do I test case sensitivity?
Check the "i (case insensitive)" box above the text to test: the pattern will then match uppercase and lowercase letters interchangeably, without having to modify it.
100% local processing: the pattern test runs in your browser via our WebAssembly module — your text is never sent to a server.