Regex Tester
Test and debug regular expressions live in your browser. Real-time match highlighting, capture groups, flags support, and common regex patterns. Free, no login required.
Enter a pattern and test string to see matches
How to Use the Regex Tester
Enter Your Pattern
Type your regular expression in the pattern field. Use the quick pattern buttons above to load common patterns like Email, URL, or Phone.
Set Flags
Toggle flags like g (global), i (case-insensitive), m (multiline) to control how matching works.
Paste Test String
Enter your test string in the left panel. Matches are highlighted in real-time as you type — no button needed.
View & Export Results
See all matches, capture groups, and indexes. Use the Replace tab to perform find-and-replace. Copy matches to clipboard in one click.
Frequently Asked Questions
This tool uses JavaScript's built-in RegExp engine (ECMAScript regex). It supports all standard features including lookaheads, lookbehinds (ES2018+), named capture groups, Unicode mode, and dotAll mode.
g (global) — Find all matches, not just the first. i (case-insensitive) — Match regardless of uppercase or lowercase. m (multiline) — ^ and $ match start/end of each line. s (dotAll) — The dot (.) matches newline characters too.
Wrap parts of your pattern in parentheses: (\w+)@(\w+). Each group gets a number starting at $1. In the Groups tab you'll see every match broken down by group. Named groups use (?<name>...) syntax.
100% safe. All processing runs entirely in your browser using JavaScript. Your test strings never leave your device and are never sent to any server. We don't log, store, or analyse any of your data.
Catastrophic backtracking is a real risk with certain patterns on large inputs. This tool applies a 200ms execution timeout — if a pattern takes too long it will stop and show a warning rather than freezing your tab.