regex101: IP v4 format validation

^start of line

Group 1([01][0-9][0-9]\.|2[0-4][0-9]\.|[0-9][0-9]\.|25[0-5]\.|[0-9]\.)

1st Alternative[01][0-9][0-9]\.

Character Class[01]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-9]

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

Character Class[0-9]

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

2nd 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)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

3rd Alternative[0-9][0-9]\.

Character Class[0-9]

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

Character Class[0-9]

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

4th Alternative25[0-5]\.

25the literal text 25

Character Class[0-5]

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

5th Alternative[0-9]\.

Character Class[0-9]

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Group 2([01][0-9][0-9]\.|2[0-4][0-9]\.|[0-9][0-9]\.|25[0-5]\.|[0-9]\.)

1st Alternative[01][0-9][0-9]\.

Character Class[01]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-9]

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

Character Class[0-9]

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

2nd 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)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

3rd Alternative[0-9][0-9]\.

Character Class[0-9]

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

Character Class[0-9]

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

4th Alternative25[0-5]\.

5th Alternative[0-9]\.

Group 3([01][0-9][0-9]\.|2[0-4][0-9]\.|[0-9][0-9]\.|25[0-5]\.|[0-9]\.)

Group 4([01][0-9][0-9]|2[0-4][0-9]|25[0-5]|[0-9][0-9]|[0-9])

$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

25 tokens

Regular Expression

^([01][0-9][0-9]\.|2[0-4][0-9]\.|[0-9][0-9]\.|25[0-5]\.|[0-9]\.)([01][0-9][0-9]\.|2[0-4][0-9]\.|[0-9][0-9]\.|25[0-5]\.|[0-9]\.)([01][0-9][0-9]\.|2[0-4][0-9]\.|[0-9][0-9]\.|25[0-5]\.|[0-9]\.)([01][0-9][0-9]|2[0-4][0-9]|25[0-5]|[0-9][0-9]|[0-9])$

New

0.0.0.0
1.1.1.1
101.101.101.101
255.255.255.255

Regular Expressions 101

Regular Expression

Substitution