Regular Expressions 101

Explanation

Pro

^start of line

Non-Capturing Group(?:0*(?:25[0-5]|2[0-4]\d|1?\d{1,2})\.){3}

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

0*the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated any number of times

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

1st Alternative25[0-5]

25the literal text 25

Character Class[0-5]

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

2nd 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

3rd Alternative1?\d{1,2}

1?optionally matches the literal 1 (49₁₀ / 61₈ / 31₁₆)

\d{1,2}a digit, repeated between 1 and 2 times

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

0*the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated any number of times

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

1st Alternative25[0-5]

25the literal text 25

Character Class[0-5]

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

2nd 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

3rd Alternative1?\d{1,2}

1?optionally matches the literal 1 (49₁₀ / 61₈ / 31₁₆)

\d{1,2}a digit, repeated between 1 and 2 times

$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

Unit Test Summary

Ready to run

Quick Reference

25 tokens

Regular Expression

^(?:0*(?:25[0-5]|2[0-4]\d|1?\d{1,2})\.){3}0*(?:25[0-5]|2[0-4]\d|1?\d{1,2})$

Unit Tests