Regular Expressions 101

Pro

^start of line

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

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

?repeats the group contents below at most once:

the literal (32₁₀ / 40₈ / 20₁₆)

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

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

$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

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

New

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

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