Regular Expressions 101

\ban ASCII word boundary

Non-Capturing Group(?:(?:0?[0-9]?[0-9]|1?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])\.??\b){4}

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

Non-Capturing Group(?:0?[0-9]?[0-9]|1?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])

1st Alternative0?[0-9]?[0-9]

0?optionally matches the literal 0 (48₁₀ / 60₈ / 30₁₆)

Character Class[0-9]?

?matches at most one character from the set below:

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

Character Class[0-9]

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

2nd Alternative1?[0-9]?[0-9]

1?optionally matches the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-9]?

?matches at most one character from the set below:

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

Character Class[0-9]

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

3rd Alternative2[0-4][0-9]

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-4]

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

Character Class[0-9]

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

4th Alternative25[0-5]

25the literal text 25

Character Class[0-5]

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

\.??optionally matches the literal . (46₁₀ / 56₈ / 2E₁₆)

\ban ASCII word boundary

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

\b(?:(?:0?[0-9]?[0-9]|1?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])\.??\b){4}

Test String
New

Should Match:
204.131.100.104
255.255.005.055
192.168.10.1
172.16.1.1
10.10.10.1
1.2.3.4
255.255.255.255
001.02.3.004
123.145.254.189:8080
1.2.3.4-4.3.20.1
4.3.2.1.9.8.7.6
Shouldnt match:
255.256.255.255
172.999.2.3
this is a string1.2.3.4
this is another 1.2.3.4string
144.109.279.255
v1.2.3.4