Regular expressions reference

Tokens and patterns you reach for during validation and log searches.

Basics

.: Any character except newline (flavor-dependent).
\d \w \s: Digit, word char, whitespace.
^ $: Start / end of string (or line with /m).
*: Zero or more of the previous atom.
+: One or more.
?: Optional (zero or one).

Groups and classes

[abc]: One of a, b, or c.
[^0-9]: Not a digit.
(…): Capturing group.
(?:…): Non-capturing group.
a|b: Alternation.

Useful patterns

^[^@\s]+@[^@\s]+\.[^@\s]+$: Loose email shape (not RFC-perfect).
https?://\S+: HTTP(S) URL-ish token in text.
\b\d{1,3}(?:\.\d{1,3}){3}\b: IPv4-looking address.

← All reference pages · Courses