Write a pattern and see what it does REGEX
Run a pattern against your text, see every match and capture group, and preview a replacement or a split. The pattern and the text stay in this tab.
The pattern
Written the way you would write it in JavaScript, between the slashes. Flags go on the right.
The text to run it against
What it does
$1 a numbered group · $<name> a named group ·
$& the whole match · $$ a literal dollar sign.
Waiting for a pattern.
Before
After
What the pattern says, in words
Where the parser cannot read a construct it says so instead of guessing.
Patterns worth keeping
Each one says what it misses. Choosing one loads it above with a sample to try it on.
Cheat sheet
How it works
REGEX uses your browser's own regex engine, including flags, named groups and lookbehind, and answers the usual questions: why only the first match is found, why the dot skips new lines, and what greedy and lazy mean.
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