Regular Expressions 101

^start of line

Negative Lookahead(?!\-)

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

Non-Capturing Group(?:(?:[a-zA-Z\d][a-zA-Z\d\-]{0,61})?[a-zA-Z\d]\.){1,126}

{1,126}repeats the group contents below between 1 and 126 times:

Non-Capturing Group(?:[a-zA-Z\d][a-zA-Z\d\-]{0,61})?

?repeats the group contents below at most once:

Character Class[a-zA-Z\d]

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

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

\da digit

Character Class[a-zA-Z\d\-]{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)

\da digit

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-zA-Z\d]

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

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

\da digit

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Negative Lookahead(?!\d+)

\d+a digit, repeated at least once

Character Class[a-zA-Z\d]{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)

\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.

Search reference

Regular Expression

^(?!\-)(?:(?:[a-zA-Z\d][a-zA-Z\d\-]{0,61})?[a-zA-Z\d]\.){1,126}(?!\d+)[a-zA-Z\d]{1,63}$

New

invalid-.domains
-domain.com
domain--.com
-domain-.-.com
domain.000
.domain.net
domain.net.
sub.-domain.com
sub.domain-.com
sub-.domain.com
-sub.domain.com

valid.domains.below
schools.k12
newTLD.clothing
good.photography
x.a-b.com
x-y.a-b.net
x-y.a-b-c.co.uk
x.0ac.com
schools.k12
newTLD.clothing
good.photography
0-1-2.3-4.co
a-----b.com

Regular Expression

Extraction