Regex Explainer (Explain a Regular Expression)
Paste a regular expression and get a plain-English, token-by-token explanation — character classes, groups, lookarounds, quantifiers, anchors and flags. Works with JavaScript and PCRE-style syntax. No AI, instant.
How to use
- 1Paste a pattern, with or without /slashes/flags.
- 2Read the explanation line by line — indented lines are inside a group.
- 3Test it on real text with our Regex Tester.
Frequently asked questions
Which regex flavours are supported?
JavaScript syntax, which covers most of what PCRE, Python and Java use (groups, lookarounds, classes, quantifiers, named groups, Unicode properties). Flavour-specific features like recursion or conditionals aren't explained.
Why does it say my regex is invalid?
The pattern is checked with your browser's regex engine first. Common causes are unbalanced parentheses or brackets, or a quantifier with nothing before it.
Is there a cron explainer too?
Yes — see our Cron Expression Explainer for crontab schedules.