regex101: IP Address

^start of line

Group 1((?:[01][0-9]{0,2}|(?:2(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1}))|[3-9][0-9]{0,1})\.){3}

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

Non-Capturing Group(?:[01][0-9]{0,2}|(?:2(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1}))|[3-9][0-9]{0,1})

1st Alternative[01][0-9]{0,2}

Character Class[01]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-9]{0,2}

{0,2}matches between 0 and 2 characters from the set below:

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

2nd Alternative(?:2(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1}))

Non-Capturing Group(?:2(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1}))

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Non-Capturing Group(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1})

1st Alternative5[0-5]{0,1}

5the literal 5 (53₁₀ / 65₈ / 35₁₆)

Character Class[0-5]{0,1}

{0,1}matches at most one character from the set below:

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

2nd Alternative[0-4][0-9]{0,1}

Character Class[0-4]

0-4one character from 0 (48₁₀) to 4 (52₁₀)

Character Class[0-9]{0,1}

{0,1}matches at most one character from the set below:

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

3rd Alternative[6-9]{0,1}

Character Class[6-9]{0,1}

{0,1}matches at most one character from the set below:

6-9one character from 6 (54₁₀) to 9 (57₁₀)

3rd Alternative[3-9][0-9]{0,1}

Character Class[3-9]

3-9one character from 3 (51₁₀) to 9 (57₁₀)

Character Class[0-9]{0,1}

{0,1}matches at most one character from the set below:

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?:[01][0-9]{0,2}|(?:2(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1}))|[3-9][0-9]{0,1})

1st Alternative[01][0-9]{0,2}

Character Class[01]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-9]{0,2}

{0,2}matches between 0 and 2 characters from the set below:

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

2nd Alternative(?:2(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1}))

Non-Capturing Group(?:2(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1}))

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Non-Capturing Group(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1})

1st Alternative5[0-5]{0,1}

2nd Alternative[0-4][0-9]{0,1}

3rd Alternative[6-9]{0,1}

3rd Alternative[3-9][0-9]{0,1}

$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

Search reference

Regular Expression

^((?:[01][0-9]{0,2}|(?:2(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1}))|[3-9][0-9]{0,1})\.){3}(?:[01][0-9]{0,2}|(?:2(?:5[0-5]{0,1}|[0-4][0-9]{0,1}|[6-9]{0,1}))|[3-9][0-9]{0,1})$

Unit Tests

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