Regular Expressions 101

Group 1((^|\.)((25[0-5])|(2[0-4]\d)|(1\d\d)|([1-9]?\d))){4}

{4}repeats the group contents below exactly 4 times:

Group 2(^|\.)

1st Alternative^

^start of line

2nd Alternative\.

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Group 3((25[0-5])|(2[0-4]\d)|(1\d\d)|([1-9]?\d))

1st Alternative(25[0-5])

Group 4(25[0-5])

25the literal text 25

Character Class[0-5]

0-5one character from 0 (48₁₀) to 5 (53₁₀)

2nd Alternative(2[0-4]\d)

Group 5(2[0-4]\d)

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-4]

0-4one character from 0 (48₁₀) to 4 (52₁₀)

\da Unicode decimal digit

3rd Alternative(1\d\d)

Group 6(1\d\d)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

\da Unicode decimal digit

4th Alternative([1-9]?\d)

Group 7([1-9]?\d)

Character Class[1-9]?

?matches at most one character from the set below:

1-9one character from 1 (49₁₀) to 9 (57₁₀)

\da Unicode decimal digit

/the literal / (47₁₀ / 57₈ / 2F₁₆)

Non-Capturing Group(?:\d|[12]\d|3[01])

1st Alternative\d

\da Unicode decimal digit

2nd Alternative[12]\d

Character Class[12]

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

\da Unicode decimal digit

3rd Alternative3[01]

3the literal 3 (51₁₀ / 63₈ / 33₁₆)

Character Class[01]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

$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.

25 tokens

Regular Expression

((^|\.)((25[0-5])|(2[0-4]\d)|(1\d\d)|([1-9]?\d))){4}/(?:\d|[12]\d|3[01])$

New

10.120.15.30/28
172.181.30.0/24
107.8.109.110/24