Regular Expressions 101

Explanation

Pro

^start of line

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

?repeats the group contents below at most once:

Character Class[a-z]

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

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])*

*repeats the group contents below any number of times:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

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)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

$end of line

Global pattern flags

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

g modifier: global. Finds all matches instead of stopping after the first

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

25 tokens

Regular Expression

^(?:[a-z](?:[a-z0-9-]*[a-z0-9])?(?:\.[a-z0-9-]*[a-z0-9])*)?\.$

New

.
a.
a-9.
abc.
abc.a-c.abc.

a.-.
 -.
-a.
a-.
a
abc.-bc
ab-.abc
abc.a-@c
..



a.b.c--d.
.
a.bb.cc.
a.b.ccc-d-e-f.
a-bB.


.a.
a--b
a..b.
.a
a.bb.cc
a.b.ccc-d-e-f
a-bB
a
..

Extraction

.
a.
a-9.
abc.
abc.a-c.abc.

a.-.
 -.
-a.
a-.
a
abc.-bc
ab-.abc
abc.a-@c
..



a.b.c--d.
.
a.bb.cc.
a.b.ccc-d-e-f.
a-bB.


.a.
a--b
a..b.
.a
a.bb.cc
a.b.ccc-d-e-f
a-bB
a
..