Regular Expressions 101

Pro

^start of line

Positive Lookahead(?=.{6,16}$)

.{6,16}any character (except for line terminators), repeated between 6 and 16 times

$end of line

Character Class[a-zA-Z]

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

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Character Class[a-zA-Z0-9]*

*matches any number of characters from the set below:

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

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Non-Capturing Group(?:-[a-zA-Z0-9]+)?

?repeats the group contents below at most once:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-zA-Z0-9]+

+matches at least one character from the set below:

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

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

$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.

25 tokens

^(?=.{6,16}$)[a-zA-Z][a-zA-Z0-9]*(?:-[a-zA-Z0-9]+)?$

New

a-aaaa
aaaaaa
Aaaaaaaaaaaaaaaa
A-dddddddddddddd

A-a-aaaaaaaaaaaa
a-aaaaaaaaaa-
-aaaaaaaaaa

a-aaaa
aaaaaa
Aaaaaaaaaaaaaaaa
A-dddddddddddddd

A-a-aaaaaaaaaaaa
a-aaaaaaaaaa-
-aaaaaaaaaa