Type a pattern and flags to instantly highlight the matching parts of your string. From checking capture groups to previewing replacements, all on one screen like an editor.
Key Features
Real-time match highlighting
As soon as you type a pattern, it highlights the matching parts of the test string like an editor.
Flag toggles
Turn the six g·i·m·s·u·y flags on and off with chips and instantly compare the difference in behavior.
Capture group inspection
See numbered groups and named capture groups along with their values and positions at a glance in the result cards.
Replacement preview
Preview the result of a replacement using $1·$·$& in real time.
Pattern library
Provides commonly used patterns like email, URL, IP, and date with explanations and examples.
Cheat sheet · guides
A syntax cheat sheet and introductory guides help you write patterns.
How to Use
- Enter a regex in the pattern box at the top and turn on the flag chips you need.
- Put the text to check in the test string box below, and the matching parts are highlighted instantly.
- In the Matches tab, check the position and capture groups of each match.
- In the Replace tab, enter a replacement to preview the changed result.
- If you're stuck, open an example from the Pattern Library and start from there.
Frequently Asked Questions
Which regex syntax do you support?
It uses the browser's JavaScript (ECMAScript) RegExp engine as is. It supports modern syntax such as named capture groups (?...), lookahead/lookbehind, and Unicode properties (the u flag).
What does each of the g·i·m·s·u·y flags mean?
g is global (all matches), i ignores case, m is multiline (^·$ apply to each line), s is dotAll (. includes line breaks), u is Unicode, and y is sticky (matches only at the lastIndex position). You can turn them on and off by clicking the chips.
How do I check capture groups and replacements?
The match result cards show numbered groups ($1, $2…) and named groups along with their values. In the Replace tab, entering a replacement using $1·$·$& lets you preview the result in real time.
Are there examples of commonly used patterns?
Yes. The Pattern Library gathers commonly used regexes such as email, URL, IP, date, HEX color, UUID, and password with explanations and examples, and you can open each pattern right in the tester.
Is the pattern or string I enter sent to a server?
No. All computation happens only inside your browser, and patterns and strings are never sent to or stored on a server.
All computation happens only inside the user's browser, and any pattern or string you enter is never sent to or stored on a server.