Regular Expressions 101

Explanation

Pro

^start of line

Non-Capturing Group(?:(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}

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

Non-Capturing Group(?:25[0-5]|2[0-4]\d|[01]?\d\d?)

1st Alternative25[0-5]

25the literal text 25

Character Class[0-5]

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

2nd Alternative2[0-4]\d

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-4]

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

\da digit

3rd Alternative[01]?\d\d?

Character Class[01]?

?matches at most one character from the set below:

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

\da digit

\d?optionally matches a digit

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?:25[0-5]|2[0-4]\d|[01]?\d\d?)

1st Alternative25[0-5]

25the literal text 25

Character Class[0-5]

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

2nd Alternative2[0-4]\d

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-4]

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

\da digit

3rd Alternative[01]?\d\d?

Character Class[01]?

?matches at most one character from the set below:

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

\da digit

\d?optionally matches a digit

$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

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

25 tokens

Regular Expression

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

New

127.0.0.1
192.168.1.1
192.168.1.255
255.255.255.255
0.0.0.0
1.1.1.01

30.168.1.255.1
127.1
192.168.1.256
-1.2.3.4
3...3

Extraction

127.0.0.1
192.168.1.1
192.168.1.255
255.255.255.255
0.0.0.0
1.1.1.01

30.168.1.255.1
127.1
192.168.1.256
-1.2.3.4
3...3