Regular Expressions 101

^start of line

Negative Lookahead(?!0+\.0+\.0+\.0+$)

0+the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

0+the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

0+the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

0+the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated at least once

$end of line

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

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

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

Non-Capturing Group(?:^|\.)

1st Alternative^

^start of line

2nd Alternative\.

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

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

1st Alternative\d

\da digit

2nd Alternative[1-9]\d

Character Class[1-9]

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

\da digit

3rd Alternative1\d{2}

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

\d{2}a digit, repeated exactly 2 times

4th Alternative2[-4]\d

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[-4]

-the literal - (45₁₀ / 55₈ / 2D₁₆)

4the literal 4 (52₁₀ / 64₈ / 34₁₆)

\da digit

5th Alternative25[0-5]

25the literal text 25

Character Class[0-5]

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

$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.

Search reference

Regular Expression

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

New

123.23.21.21
0.0.0.0
127.0.0.1