Regular Expressions 101

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

Detailed match information will be displayed here automatically.

Search reference

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