Regular Expressions 101

(?im)applies the following effective flags to the remainder of the pattern: gmi

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

^start of line

Positive Lookahead(?=\*|.+\*$)

1st Alternative\*

\*the literal * (42₁₀ / 52₈ / 2A₁₆)

2nd Alternative.+\*$

.+any character (except for line terminators), repeated at least once

\*the literal * (42₁₀ / 52₈ / 2A₁₆)

$end of line

Non-Capturing Group(?:\*[.-]?)?

?repeats the group contents below at most once:

\*the literal * (42₁₀ / 52₈ / 2A₁₆)

Character Class[.-]?

?matches at most one character from the set below:

.the literal . (46₁₀ / 56₈ / 2E₁₆)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-z0-9]

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

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

Non-Capturing Group(?:[a-z0-9-]*[a-z0-9])?

?repeats the group contents below at most once:

Character Class[a-z0-9-]*

*matches any number of characters from the set below:

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

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

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-z0-9]

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

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

Non-Capturing Group(?:\.[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)*

*repeats the group contents below any number of times:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Character Class[a-z0-9]

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

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

Non-Capturing Group(?:[a-z0-9-]*[a-z0-9])?

?repeats the group contents below at most once:

Character Class[a-z0-9-]*

*matches any number of characters from the set below:

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

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

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-z0-9]

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

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

Non-Capturing Group(?:[.-]?\*)?

?repeats the group contents below at most once:

Character Class[.-]?

?matches at most one character from the set below:

.the literal . (46₁₀ / 56₈ / 2E₁₆)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\*the literal * (42₁₀ / 52₈ / 2A₁₆)

$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

(?im)^(?=\*|.+\*$)(?:\*[.-]?)?[a-z0-9](?:[a-z0-9-]*[a-z0-9])?(?:\.[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)*(?:[.-]?\*)?$

New

*test.com
*.test.com
*test
test.*
test*
*test*

Substitution