Regular Expressions 101

^start of line

Group 1([a-z0-9]+((?=\..+@.+\..+)[a-z0-9.]*@[a-z0-9]*\.[a-z0-9]*))

Character Class[a-z0-9]+

+matches at least one character from the set below:

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

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

Group 2((?=\..+@.+\..+)[a-z0-9.]*@[a-z0-9]*\.[a-z0-9]*)

Positive Lookahead(?=\..+@.+\..+)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

.+any character (except for line terminators), repeated at least once

@the literal @ (64₁₀ / 100₈ / 40₁₆)

.+any character (except for line terminators), repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

.+any character (except for line terminators), repeated at least once

Character Class[a-z0-9.]*

*matches any number of characters from the set below:

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

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

.the literal . (46₁₀ / 56₈ / 2E₁₆)

@the literal @ (64₁₀ / 100₈ / 40₁₆)

Character Class[a-z0-9]*

*matches any number of characters from the set below:

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

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Character Class[a-z0-9]*

*matches any number of characters from the set below:

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

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

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

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Search reference

Regular Expression

^([a-z0-9]+((?=\..+@.+\..+)[a-z0-9.]*@[a-z0-9]*\.[a-z0-9]*))$

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