What regex flavor does this use?

JavaScript's built-in RegExp — the same engine used in Node.js and all browsers. Most common regex features (quantifiers, groups, lookaheads) work as expected.

Toggle the flags (g, i, m, s) using the buttons next to the pattern input. Global (g) finds all matches, case-insensitive (i) ignores case, multiline (m) changes ^ and $ behavior.

Why isn't my regex matching?

Common issues: forgetting to escape special characters (. matches any char, not a literal dot), missing the global flag for multiple matches, or anchors (^$) not matching in multiline mode.

Is my data sent to a server?

No. Regex matching runs entirely in your browser.

Regex Tester

Test regex patterns against text with live match highlighting. Free online regex tester.

Frequently asked questions

Regex Tester — Test Regular Expressions Online Free

Write a regex pattern and see matches highlighted in real time against your test string. Supports JavaScript regex syntax with toggleable flags. Great for building and debugging regular expressions.

Live matching

Matches highlight as you type — both the pattern and test string are reactive.

Match details

See all match groups, indices, and captured groups.

Flag toggles

Toggle global, case-insensitive, multiline, and dotAll flags with buttons.