Regex Tester & Debugger
Build, test and debug your regular expressions with real-time highlighting and explanation.
Cheat Sheet
. Any char\d Digit\w Word char\s Whitespace+ 1 or more* 0 or moreShortcuts
^ Start$ End(x) Group[abc] Set3 Exact qty? OptionalHow to Use Regex Tester & Debugger
Frequently Asked Questions
What is a Regular Expression (Regex)?
A Regular Expression is a sequence of characters that forms a search pattern. It is used for string matching, search-and-replace, and validation in almost all programming languages.
How do I use the flags?
Common flags include 'g' (Global: find all matches), 'i' (Case-insensitive), and 'm' (Multiline: ^ and $ match start/end of lines). Click the buttons above the pattern input to toggle them.
What is a Capture Group?
Parts of a regex pattern enclosed in parentheses () are called capture groups. They allow you to extract specific parts of a match separately.
Does this support negative lookahead?
Yes, this uses the built-in JavaScript engine which supports lookahead, lookbehind (in modern browsers), and common regex features.
Is my data private?
100% private. All regex processing happens entirely in your browser. Your regex and test data are never sent to our servers.