Write a regular expression and see every match and group highlighted live, with a plain-English explanation of the pattern.
Turn flags on and off: g all matches, i ignore case, m multi-line, s dot matches newline, u Unicode.
Matches are highlighted and groups shaded as you type.
Read the plain-English explanation and try a replacement.
JavaScript, as built into your browser. Most patterns work the same in Python, PHP and Java, but look-behind and named groups can differ.
Some patterns take exponentially long on certain text (“catastrophic backtracking”). We stop after 1 second and point to the part that’s slow.
No. Matching runs entirely in your browser.