regex101: Match RFC1918 And Localhost

Explanation

Pro

^start of line

Non-Capturing Group(?:(?:10\.\d{1,3}\.\d{1,3}\.\d{1,3}|172\.(?:(?:1[6-9])|(?:2[0-9])|(?:3[0-1]))\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|127\.\d{1,3}\.\d{1,3}\.\d{1,3})(?::\d{1,5})?)

Non-Capturing Group(?:10\.\d{1,3}\.\d{1,3}\.\d{1,3}|172\.(?:(?:1[6-9])|(?:2[0-9])|(?:3[0-1]))\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|127\.\d{1,3}\.\d{1,3}\.\d{1,3})

1st Alternative10\.\d{1,3}\.\d{1,3}\.\d{1,3}

10the literal text 10

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

2nd Alternative172\.(?:(?:1[6-9])|(?:2[0-9])|(?:3[0-1]))\.\d{1,3}\.\d{1,3}

172the literal text 172

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Non-Capturing Group(?:(?:1[6-9])|(?:2[0-9])|(?:3[0-1]))

1st Alternative(?:1[6-9])

Non-Capturing Group(?:1[6-9])

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[6-9]

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

2nd Alternative(?:2[0-9])

Non-Capturing Group(?:2[0-9])

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Character Class[0-9]

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

3rd Alternative(?:3[0-1])

Non-Capturing Group(?:3[0-1])

3the literal 3 (51₁₀ / 63₈ / 33₁₆)

Character Class[0-1]

0-1one character from 0 (48₁₀) to 1 (49₁₀)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

3rd Alternative192\.168\.\d{1,3}\.\d{1,3}

192the literal text 192

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

168the literal text 168

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

4th Alternative127\.\d{1,3}\.\d{1,3}\.\d{1,3}

127the literal text 127

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

Non-Capturing Group(?::\d{1,5})?

?repeats the group contents below at most once:

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\d{1,5}a digit, repeated between 1 and 5 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

Quick Reference

25 tokens

Regular Expression

^(?:(?:10\.\d{1,3}\.\d{1,3}\.\d{1,3}|172\.(?:(?:1[6-9])|(?:2[0-9])|(?:3[0-1]))\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|127\.\d{1,3}\.\d{1,3}\.\d{1,3})(?::\d{1,5})?)$

New

127.0.0.1
127.255.255.255
127.0.0.1:3000
10.0.0.1
10.0.0.2
10.0.1.1
10.0.1.2:443
172.16.0.1
172.16.0.2
172.16.1.1
172.16.1.2
192.168.0.1
192.168.0.2
192.168.1.1
192.168.1.2
10.10.10.1
10.10.10.2
172.31.255.1
172.31.255.2
192.168.100.1
192.168.100.2
10.255.255.1
10.255.255.2
8.8.8.8:80
1.1.1.1
1.0.0.1
198.41.0.4
64.233.160.0
208.67.222.222:8080