Regular Expressions 101

Pro

^start of line

Negative Lookahead(?!.*\b(?:admin|alfred)\b)

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

\ban ASCII word boundary

Non-Capturing Group(?:admin|alfred)

1st Alternativeadmin

adminthe literal text admin (case sensitive)

2nd Alternativealfred

alfredthe literal text alfred (case sensitive)

\ban ASCII word boundary

Character Class[a-zA-Z\d]+

+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)

\da digit

Non-Capturing Group(?: [a-zA-Z\d]+)+

+repeats the group contents below at least once:

the literal (32₁₀ / 40₈ / 20₁₆)

Character Class[a-zA-Z\d]+

+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)

\da digit

$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

^(?!.*\b(?:admin|alfred)\b)[a-zA-Z\d]+(?: [a-zA-Z\d]+)+$

New

admin may not be used
it may not be used by admin
admin
username
username here