Regex Tester
Write and debug regular expressions with instant match highlighting, flag toggles (g, i, m, s), and detailed capture group extraction.
Regex Flags Reference
gGlobal
Find all matches, not just the first one
iInsensitive
Case-insensitive matching (a matches A)
mMultiline
^ and $ match the start/end of each line
sDotall
The dot . matches newlines as well
Frequently Asked Questions
What regex flavour does this use?
This tool uses the JavaScript ECMAScript regular expression engine (built into all modern browsers). It supports standard regex syntax including lookaheads, backreferences, named capture groups, and unicode properties.
How do I capture groups?
Wrap parts of your pattern in parentheses. For example /([a-z]+)@([a-z]+)\.([a-z]+)/i captures 3 groups from an email address. The tool shows each group's matched text in the details panel.
Is there a limit on how many matches are shown?
Yes, the tool displays up to 500 matches to keep the browser responsive. For most real-world patterns this limit is never reached.