Regular Expressions 101

Pro

^start of line

Negative Lookahead(?!\d)

\da digit

Negative Lookahead(?!.*-.*-)

.*any character (except for line terminators), repeated any number of times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

.*any character (except for line terminators), repeated any number of times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Negative Lookahead(?!.*-$)

.*any character (except for line terminators), repeated any number of times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

$end of line

Negative Lookahead(?!-)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-zA-Z0-9-]{6,20}

{6,20}matches between 6 and 20 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)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

$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.

26 tokens

Regular Expression

^(?!\d)(?!.*-.*-)(?!.*-$)(?!-)[a-zA-Z0-9-]{6,20}$

New

abc123
abc-123

ab12
-abc123
abc123-
ab-12-c3
123abc

The username can contain English letters, numbers and one hyphen (-).

The username cannot be started with hyphen (-).

The username cannot be finished with hyphen (-).

The username cannot be started with numbers.

The username cannot contain more than one hyphen (-).

Minimum is 6 and Maximum 20.