Regular Expressions 101

Explanation

Pro

Negative Lookahead(?![\d.]+)

Character Class[\d.]+

+matches at least one character from the set below:

\da digit

.the literal . (46₁₀ / 56₈ / 2E₁₆)

Group 1((?!-))

Negative Lookahead(?!-)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Group 2(xn--)?

?repeats the group contents below at most once:

xn--the literal text xn-- (case sensitive)

Character Class[a-z0-9]

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

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

Character Class[a-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)

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

-the literal - (45₁₀ / 55₈ / 2D₁₆)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

Character Class[a-z0-9]{0,1}

{0,1}matches at most one character 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 . (46₁₀ / 56₈ / 2E₁₆)

Group 3(xn--)?

?repeats the group contents below at most once:

xn--the literal text xn-- (case sensitive)

Group 4([a-z0-9\._-]{1,61}|[a-z0-9-]{1,30})

1st Alternative[a-z0-9\._-]{1,61}

Character Class[a-z0-9\._-]{1,61}

{1,61}matches between 1 and 61 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 . (46₁₀ / 56₈ / 2E₁₆)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

2nd Alternative[a-z0-9-]{1,30}

Character Class[a-z0-9-]{1,30}

{1,30}matches between 1 and 30 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 - (45₁₀ / 55₈ / 2D₁₆)

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

(?![\d.]+)((?!-))(xn--)?[a-z0-9][a-z0-9-_]{0,61}[a-z0-9]{0,1}\.(xn--)?([a-z0-9\._-]{1,61}|[a-z0-9-]{1,30})

New

www.example.com
subdomain.example.com
subdomain.example.co.uk

192.168.0.0
127.0.0.1

Lucia told me about www.example.com. However, whenever I visit the site the IP 127.0.0.1  shows up.

Extraction

www.example.com
subdomain.example.com
subdomain.example.co.uk

192.168.0.0
127.0.0.1

Lucia told me about www.example.com. However, whenever I visit the site the IP 127.0.0.1  shows up.