Regex Explainer

Explains a regular expression token by token.

The Regex Explainer breaks a regular expression down token by token, pairing each part of the pattern with a plain-English description of what it matches. Paste a regex and it walks through escapes like \d and \w, character sets, groups, anchors, and quantifiers so you can understand or sanity-check a pattern without parsing it in your head. It runs entirely in your browser, which makes it handy for quickly decoding unfamiliar patterns from code reviews, logs, or config files.

Common uses

• Decode an unfamiliar regex copied from someone else's code or a Stack Overflow answer.
• Sanity-check your own pattern by confirming each token does what you expect.
• Learn regex syntax by seeing how anchors, groups, and quantifiers are described.
• Document a pattern by listing its tokens and meanings during a code review.
• Spot mistakes such as an unintended character set or a misplaced quantifier.

FAQ

Is my regex sent to a server?

No. The tool runs entirely in your browser and nothing is uploaded. Your pattern never leaves your device.

What regex tokens does it recognize?

It explains escape sequences (\d, \D, \w, \W, \s, \S, \b), character sets including negated ones, capturing and non-capturing (?:) groups, the anchors ^ and $, the quantifiers *, + and ?, alternation with |, and brace quantifiers like {3}, {2,5} and {2,}.

Does it tell me whether my regex is valid?

No. It does not compile or validate the pattern; it walks the string and describes each token it recognizes. Anything it does not recognize is reported as a literal character.

Which regex flavor does it assume?

It is geared toward common JavaScript-style regex syntax. Flags (such as g, i or m) and lookahead or lookbehind groups are not specially interpreted.

What happens with an empty input?

An empty or whitespace-only input produces an error asking you to enter a regular expression to explain.

Related tools

• Regex Cheatsheet
• Regex Tester