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Regex Explainer

Break a regular expression into tokens and explain each one in plain English.

A regex explainer tokenises a regular expression and describes each part in plain English — anchors, character classes, quantifiers, groups, lookarounds and back-references — so you can read a pattern someone else wrote, or confirm that yours says what you meant.

Runs in your browser
Privacy
Runs entirely in your browser — nothing is uploaded
Cost
Free, unlimited, no sign-up

Frequently asked questions

Why is my regex so slow?

Usually catastrophic backtracking — nested quantifiers such as (a+)+ force the engine to try exponentially many ways to match a failing string. A pattern that runs instantly on valid input can hang for minutes on a slightly malformed one.

Should I use a regex to parse HTML?

No. HTML is nested and context-dependent, which a regular expression cannot express. Use a parser. Regexes are right for tokens with a fixed shape — a postcode, a timestamp, a hex colour.

How to use the regex explainer

  1. 1Enter or paste your pattern.
  2. 2Enter or paste your flags.
  3. 3The result appears immediately — copy or download it.

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