Explain a regular expression in English

Explain each token, group, quantifier, and assertion in a JavaScript regular expression.

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ToolRegex Explainer
Input
Output
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How it works

The expression is tokenized into literals, character classes, groups, quantifiers, assertions, and alternations; each token is described with its matching scope. The explanation follows JavaScript syntax and does not execute replacement code.

  • JavaScript syntax is a common browser baseline.
  • Flags are shown separately because they alter matching behavior.

Worked example

Explain email validation regex in plain English
Get a plain English explanation of an email validation regex
Input
											^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$
Output
												Pattern: /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/

This regex matches: at the start of the string, then any character in [a-zA-Z0-9._%+-], then repeated one or more times, then the character '@', then any character in [a-zA-Z0-9.-], then repeated one or more times, then the literal character '.', then any character in [a-zA-Z], then repeated 2 or more times, then at the end of the string

When to use this

Validation docs, code reviews, and support debugging explain regex tokens.

Edge cases

  • A greedy quantifier can consume text needed by a later group.
  • A hyphen in a character class changes meaning by position.
  • Escapes differ between regex literals and string constructors.

References