Regular Expressions 101

Negative Lookbehind(?<!\S)

\Sany non-whitespace character

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

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

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

1st Alternative[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 digit

2nd Alternative1\d\d

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

\da digit

3rd 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

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

Negative Lookahead(?!\S)

\Sany non-whitespace character

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

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

New

IP-salata 1555.2655.3255.1594 0.0.0.0 256.1.2.3 1.2.3.4 255.0.0.1 tomata