Regular Expressions 101

Non-Capturing Group(?:[12]?\d{1,2}\.){3}

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

Character Class[12]?

?matches at most one character from the set below:

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

\d{1,2}a digit, repeated between 1 and 2 times

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Character Class[12]?

?matches at most one character from the set below:

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

\d{1,2}a digit, repeated between 1 and 2 times

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

(?:[12]?\d{1,2}\.){3}[12]?\d{1,2}

New

127.0.0.1
192.168.101.100
255.255.0.0

....
1..0.1