Regular Expressions 101

^start of line

Group 1((([a-z\d](-?[a-z\d]){0,62})\.)*(([a-z\d](-?[a-z\d]){0,62})\.)([a-z](-?[a-z\d]){1,62})|((\d{1,3}\.){3}\d{1,3}))

1st Alternative(([a-z\d](-?[a-z\d]){0,62})\.)*(([a-z\d](-?[a-z\d]){0,62})\.)([a-z](-?[a-z\d]){1,62})

Group 2(([a-z\d](-?[a-z\d]){0,62})\.)*

*repeats the group contents below any number of times:

Group 3([a-z\d](-?[a-z\d]){0,62})

Character Class[a-z\d]

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

\da Unicode decimal digit

Group 4(-?[a-z\d]){0,62}

{0,62}repeats the group contents below between 0 and 62 times:

-?optionally matches the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-z\d]

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

\da Unicode decimal digit

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Group 5(([a-z\d](-?[a-z\d]){0,62})\.)

Group 6([a-z\d](-?[a-z\d]){0,62})

Character Class[a-z\d]

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

\da Unicode decimal digit

Group 7(-?[a-z\d]){0,62}

{0,62}repeats the group contents below between 0 and 62 times:

-?optionally matches the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-z\d]

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

\da Unicode decimal digit

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Group 8([a-z](-?[a-z\d]){1,62})

Character Class[a-z]

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

Group 9(-?[a-z\d]){1,62}

{1,62}repeats the group contents below between 1 and 62 times:

-?optionally matches the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-z\d]

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

\da Unicode decimal digit

2nd Alternative((\d{1,3}\.){3}\d{1,3})

Group 10((\d{1,3}\.){3}\d{1,3})

Group 11(\d{1,3}\.){3}

{3}repeats the group contents below exactly 3 times:

\d{1,3}a Unicode decimal digit, repeated between 1 and 3 times

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a Unicode decimal digit, repeated between 1 and 3 times

$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-z\d](-?[a-z\d]){0,62})\.)*(([a-z\d](-?[a-z\d]){0,62})\.)([a-z](-?[a-z\d]){1,62})|((\d{1,3}\.){3}\d{1,3}))$

Test String
New

// Valid
a-a.domain.com
1a.domain.com
a1.domain.com
a.domain.com
domain.com
10.10.10.11
// Invalid
-a.domain.com
a-.domain.com

// Valid
cname.do-main.com
cname.1domain.com
cname.domain1.com
// Invalid
cname.-domain.com
cname.domain-.com

// Valid
cname.domain.tld
cname.domain.co
cname.domain.tld1
cname.domain.tld-1
// Invalid
cname.domain.1tld
cname.domain.tld-
cname.domain.-tld

Substitution
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