regex101: JavaScript Match Workspace

^start of line

Group 1(((1?[1-9]?|10|2[0-4])\d|25[0-5])($|\.(?!$))){4}

{4}repeats the group contents below exactly 4 times:

Group 2((1?[1-9]?|10|2[0-4])\d|25[0-5])

1st Alternative(1?[1-9]?|10|2[0-4])\d

Group 3(1?[1-9]?|10|2[0-4])

1st Alternative1?[1-9]?

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

Character Class[1-9]?

?matches at most one character from the set below:

1-9one character from 1 (49₁₀) to 9 (57₁₀)

2nd Alternative10

10the literal text 10

3rd Alternative2[0-4]

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-4]

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

\da digit

2nd Alternative25[0-5]

25the literal text 25

Character Class[0-5]

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

Group 4($|\.(?!$))

1st Alternative$

$end of line

2nd Alternative\.(?!$)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Negative Lookahead(?!$)

$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

26 tokens

Regular Expression

^(((1?[1-9]?|10|2[0-4])\d|25[0-5])($|\.(?!$))){4}$

New

validates:
192.68.35.35
0.0.0.0
255.0.0.0
192.168.1.0
192.168.0.1
255.255.255.0
1.1.1.1
255.255.255.255
249.249.249.249
200.200.200.200
199.199.199.199
100.100.100.100
99.99.99.99
0.0.0.0
9.9.9.9
10.10.10.10
99.99.99.99
100.100.100.100
109.109.109.109
110.110.110.110
199.199.199.199
200.200.200.200
249.249.249.249
250.250.250.250
255.255.255.255

should not validate:
256.256.256.260
192.168.0.0/24
192.168..1
192.168.1
1
1.
1.1
1.1.
1.1.1
1.1.1.
1.1.1.1.
1.1.1.1.1
.1.1.1.1
01.01.01.01
09.09.09.09
1.0.0.1.0
010.1.1.1
123456
123123123123
.127.0.0.1

Regular Expressions 101

Regular Expression

Substitution