Regular Expressions 101

^start of string

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

Negative Lookahead(?![0.]+$)

Character Class[0.]+

+matches at least one character from the set below:

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

.the literal . (46₁₀ / 56₈ / 2E₁₆)

$end of string, or before its final line terminator

Non-Capturing Group(?: (?:^|\.) (?: \d|[1-9][0-9]|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 string

2nd Alternative\.

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

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

1st Alternative \d

\da digit

2nd Alternative[1-9][0-9]

Character Class[1-9]

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

Character Class[0-9]

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

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 string, or before its final line terminator

Global pattern flags

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

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

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