Regex Tester
Developer ToolsTest regular expressions live with match highlighting, capture group display, flag toggles, and a built-in regex syntax reference cheat sheet.
Regular Expression
/
/gi
2 matches
Match Details
Match 1·index 14
Full
hello@example.comGroup 1
helloGroup 2
example.comMatch 2·index 35
Full
support@devtools.ioGroup 1
supportGroup 2
devtools.ioPattern Explanation6 tokens
(\w+)@(\w+\.\w+)
(—Start of capturing group\w—Word character [a-zA-Z0-9_]+—1+ times (greedy))—End of group@—Literal character "@"\.—Escaped literal "."About Regex Tester
The Regex Tester gives you a live sandbox to write, debug, and understand regular expressions in real time. Paste your test string and pattern to see every match highlighted as you type, with numbered capture groups and named group values displayed clearly below. Toggle flags like global, case-insensitive, multiline, and dotall without leaving the page. A built-in syntax reference covers quantifiers, anchors, character classes, lookaheads, and more — perfect for beginners learning regex and experts verifying complex patterns.
Features
- ✓Live match highlighting as you type the pattern
- ✓Numbered and named capture group display
- ✓Global, case-insensitive, multiline, dotall, and sticky flag toggles
- ✓Match count and position (index/length) for each match
- ✓Substitution mode to preview replace() results
- ✓Built-in regex syntax cheat sheet with examples
- ✓Support for JavaScript RegExp syntax
- ✓Color-coded overlapping and adjacent match visualization
Common Use Cases
- Validating email, phone, or URL formats in form input
- Extracting structured data from log files or raw text
- Writing search-and-replace patterns for code editors
- Learning regex syntax with immediate visual feedback
- Debugging regex patterns that give unexpected results
- Building input validation rules for web applications
Frequently Asked Questions
QWhich regex flavor does this tool use?
The tester uses JavaScript's built-in RegExp engine, which supports ES2018+ features including named capture groups, lookbehind assertions, and Unicode property escapes.
QCan I test multiline strings?
Yes. Use Shift+Enter to insert newlines in the test input, or paste multiline text directly. Enable the multiline flag (m) to make ^ and $ match line boundaries.
QHow do I use named capture groups?
Use the syntax (?<name>pattern) in your regex. Named groups appear alongside numbered groups in the match results panel.
QDoes the substitution mode support backreferences?
Yes. In the replacement string, use $1, $2, or $<name> to reference capture groups, and $& for the full match.