Regular Expressions 101

Explanation

Pro

Group 1(([a-zA-Z0-9]{1,63}|[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9])\.){0,3}

{0,3}repeats the group contents below between 0 and 3 times:

Group 2([a-zA-Z0-9]{1,63}|[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9])

1st Alternative[a-zA-Z0-9]{1,63}

Character Class[a-zA-Z0-9]{1,63}

{1,63}matches between 1 and 63 characters 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)

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

2nd Alternative[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9]

Character Class[a-zA-Z0-9]

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

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

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

Character Class[a-zA-Z0-9-]{0,61}

{0,61}matches between 0 and 61 characters 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)

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

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-zA-Z0-9]

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

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

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Character Class[a-zA-Z]{2,63}

{2,63}matches between 2 and 63 characters 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)

\ban ASCII word boundary

Negative Lookahead(?!\.)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

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

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

25 tokens

Regular Expression

(([a-zA-Z0-9]{1,63}|[a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9])\.){0,3}[a-zA-Z]{2,63}\b(?!\.)

New

site.com 1.site.com 2.1.site.com 3.2.1.site.com  4.3.2.1.site.com, 5.4.3.2.1.site.com

Extraction

site.com 1.site.com 2.1.site.com 3.2.1.site.com  4.3.2.1.site.com, 5.4.3.2.1.site.com