Regex Tester
Test regular expressions against strings with live match highlighting.
Frequently Asked Questions
What are regular expressions?
A regular expression (regex) is a sequence of characters that specifies a search pattern. They are used in almost all programming languages for string searching, manipulation, and input validation — like checking whether an email address is formatted correctly.
What do the flags mean?
g (global) finds all matches rather than stopping after the first; i (ignore case) makes the whole expression case-insensitive; m (multiline) makes ^ and $ match the start and end of each line; s (dotall) lets the dot match newline characters as well.
Which regex flavor is this?
Standard JavaScript (ECMAScript) RegExp. It is very close to PCRE (PHP/Perl) and Python's re module, with minor differences around lookbehind support and some escape sequences.