Regular Expressions 101

^start of line

Negative Lookahead(?!.{31})

.{31}any character (except for line terminators), repeated exactly 31 times

Character Class[a-z]+

+matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

Non-Capturing Group(?:-[a-z]+)*

*repeats the group contents below any number of times:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-z]+

+matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^(?!.{31})[a-z]+(?:-[a-z]+)*$

New

TRUE
a-b
ab-cd
abc
a-b-c

FALSE
a-
-a
a--b