Regular Expressions 101

Explanation

Pro

^start of line

Group 1([a-z][a-z0-9]{1,13}[_.\-]?[a-z0-9]{1,13})

Character Class[a-z]

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

Character Class[a-z0-9]{1,13}

{1,13}matches between 1 and 13 characters from the set below:

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

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

Character Class[_.\-]?

?matches at most one character from the set below:

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

.the literal . (46₁₀ / 56₈ / 2E₁₆)

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-z0-9]{1,13}

{1,13}matches between 1 and 13 characters from the set below:

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

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

@the literal @ (64₁₀ / 100₈ / 40₁₆)

Group 2((([0-9]{1,3})([.]{1})([0-9]{1,3})([.]{1})([0-9]{1,3})([.]{1})([0-9]{1,3}))|([a-z0-9]{1,10}[\-]?[a-z0-9]{1,10}[.]?[a-z0-9-]{1,10}[.]{1}[a-z]{2,4}))

1st Alternative(([0-9]{1,3})([.]{1})([0-9]{1,3})([.]{1})([0-9]{1,3})([.]{1})([0-9]{1,3}))

Group 3(([0-9]{1,3})([.]{1})([0-9]{1,3})([.]{1})([0-9]{1,3})([.]{1})([0-9]{1,3}))

Group 4([0-9]{1,3})

Character Class[0-9]{1,3}

{1,3}matches between 1 and 3 characters from the set below:

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

Group 5([.]{1})

Character Class[.]{1}

{1}matches one character from the set below:

.the literal . (46₁₀ / 56₈ / 2E₁₆)

Group 6([0-9]{1,3})

Character Class[0-9]{1,3}

{1,3}matches between 1 and 3 characters from the set below:

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

Group 7([.]{1})

Character Class[.]{1}

{1}matches one character from the set below:

.the literal . (46₁₀ / 56₈ / 2E₁₆)

Group 8([0-9]{1,3})

Character Class[0-9]{1,3}

{1,3}matches between 1 and 3 characters from the set below:

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

Group 9([.]{1})

Character Class[.]{1}

{1}matches one character from the set below:

.the literal . (46₁₀ / 56₈ / 2E₁₆)

Group 10([0-9]{1,3})

Character Class[0-9]{1,3}

{1,3}matches between 1 and 3 characters from the set below:

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

2nd Alternative([a-z0-9]{1,10}[\-]?[a-z0-9]{1,10}[.]?[a-z0-9-]{1,10}[.]{1}[a-z]{2,4})

Group 11([a-z0-9]{1,10}[\-]?[a-z0-9]{1,10}[.]?[a-z0-9-]{1,10}[.]{1}[a-z]{2,4})

Character Class[a-z0-9]{1,10}

{1,10}matches between 1 and 10 characters from the set below:

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

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

Character Class[\-]?

Character Class[a-z0-9]{1,10}

Character Class[.]?

Character Class[a-z0-9-]{1,10}

Character Class[.]{1}

Character Class[a-z]{2,4}

$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

Unit Test Summary

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Quick Reference

26 tokens

Regular Expression

^([a-z][a-z0-9]{1,13}[_.\-]?[a-z0-9]{1,13})@((([0-9]{1,3})([.]{1})([0-9]{1,3})([.]{1})([0-9]{1,3})([.]{1})([0-9]{1,3}))|([a-z0-9]{1,10}[\-]?[a-z0-9]{1,10}[.]?[a-z0-9-]{1,10}[.]{1}[a-z]{2,4}))$

Unit Tests

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