Regular Expressions 101

Explanation

Pro

^start of line

Positive Lookahead(?=@?[A-Za-z0-9])

@?optionally matches the literal @ (64₁₀ / 100₈ / 40₁₆)

Character Class[A-Za-z0-9]

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

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

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

Character Class[A-Za-z0-9]*

*matches any number of characters from the set below:

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

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

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

@?optionally matches the literal @ (64₁₀ / 100₈ / 40₁₆)

Character Class[A-Za-z0-9]*

*matches any number of characters from the set below:

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

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

^(?=@?[A-Za-z0-9])[A-Za-z0-9]*@?[A-Za-z0-9]*$

New

Ab01@
Ab0@1
@Ab01
Ab01
@ff@
@

Ab01@
Ab0@1
@Ab01
Ab01
@ff@
@