Regex Cheatsheet for 2026

Regex is the Swiss Army knife of string processing. The syntax is dense; this cheatsheet covers what you reach for daily.

Character Classes

PatternMatches

|---------|---------|

\ddigit \Dnon-digit \wword char (a-z, A-Z, 0-9, _) \Wnon-word \swhitespace \Snon-whitespace .any char (no newline by default) [abc]a, b, or c [^abc]anything except a, b, c [a-z]range

Quantifiers

PatternMeaning

|---------|---------|

*0 or more +1 or more ?0 or 1 {n}exactly n {n,}n or more {n,m}between n and m +?, *?non-greedy

Anchors

^ — start of string (or line with m flag)
$ — end of string (or line with m flag)
\b — word boundary
\B — non-word boundary

Groups and References

(abc) — capture group
(?:abc) — non-capturing
(?abc) — named capture
\1 — backreference to group 1
\k — backreference to named group

Lookarounds

(?=foo) — positive lookahead
(?!foo) — negative lookahead
(?<=foo) — positive lookbehind
(? — negative lookbehind


Common Patterns
Email:        ^[\w.+-]+@[\w-]+\.[\w.-]+$
URL (basic):  https?://[\w.-]+(?:/[\w./?=&%-]*)?
IPv4:         ^(?:(?:25[0-5]|2[0-4]\d|[01]?\d?\d)\.){3}(?:25[0-5]|2[0-4]\d|[01]?\d?\d)$
ISO date:     ^\d{4}-\d{2}-\d{2}$
UUID v4:      ^[a-f0-9]{8}-[a-f0-9]{4}-4[a-f0-9]{3}-[89ab][a-f0-9]{3}-[a-f0-9]{12}$
Slug:         ^[a-z0-9]+(?:-[a-z0-9]+)*$
FlagsFlagEffect
|------|--------|
gglobal
icase-insensitive
mmultiline
sdotall
uunicode
vunicode set notation
ystickyTips
Test patterns interactively before deploying.
Catastrophic backtracking is real: avoid (a+)+.
Email regex perfection is impossible; validate by sending a confirmation.

Try patterns interactively in the [Regex Tester](https://sdk.is/regex-tester).