Regular Expressions 101

Explanation

Pro

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

^start of line

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

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

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

1st Alternative1?\d{1,2}

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

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

2nd Alternative2([0-4]\d|5[0-5])

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Group 3([0-4]\d|5[0-5])

1st Alternative[0-4]\d

Character Class[0-4]

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

\da digit

2nd Alternative5[0-5]

5the literal 5 (53₁₀ / 65₈ / 35₁₆)

Character Class[0-5]

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

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

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

1st Alternative1?\d{1,2}

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

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

2nd Alternative2([0-4]\d|5[0-5])

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Group 5([0-4]\d|5[0-5])

1st Alternative[0-4]\d

Character Class[0-4]

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

\da digit

2nd Alternative5[0-5]

5the literal 5 (53₁₀ / 65₈ / 35₁₆)

Character Class[0-5]

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

$end of line

2nd Alternative^$

^start of line

$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

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

25 tokens

Regular Expression

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

New

192.168.1.1

192.168.255.255

8.8.8.8

10.10.1.1

021.8.8.8

8.021.021.8

0.0.0.0

1.0.0.0

100.10.1.1

20.200.2.2

255.255.255.254

266.274.255.0

200.249.255.8

0.0.0.0

1.0.0.0

Substitution

192.168.1.1

192.168.255.255

8.8.8.8

10.10.1.1

021.8.8.8

8.021.021.8

0.0.0.0

1.0.0.0

100.10.1.1

20.200.2.2

255.255.255.254

266.274.255.0

200.249.255.8

0.0.0.0

1.0.0.0