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IPv4 AddressRegex — Pattern, Examples & Code

^((25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)$

What it matches / doesn't match

Matches ✅Does not match ❌
●192.168.1.1●256.1.1.1
●10.0.0.0●192.168.1
●255.255.255.0●1.2.3.4.5

How it works

Each of the four octets is matched by a branch that accepts 250–255, 200–249, or 0–199 (with optional leading zero for single and double digit values). The pattern ensures each octet stays within the valid 0–255 range without relying on post-match numeric comparison. Leading zeros like 192.168.01.1 are permitted by this pattern.

Code Usage

JavaScript

const regex = /^((25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)$/;
regex.test("192.168.1.1"); // true

Python

import re
pattern = re.compile(r'^((25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)$')
bool(pattern.match("192.168.1.1"))  # True

Go

import "regexp"
r := regexp.MustCompile(`^((25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)$`)
r.MatchString("192.168.1.1") // true

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FAQ

What does the IPv4 Address regex pattern match?

Each of the four octets is matched by a branch that accepts 250–255, 200–249, or 0–199 (with optional leading zero for single and double digit values). The pattern ensures each octet stays within the valid 0–255 range without relying on post-match numeric comparison. Leading zeros like 192.168.01.1 are permitted by this pattern.

How do I use the IPv4 Address regex in JavaScript?

const regex = /^((25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)$/; regex.test("192.168.1.1"); // true

Can I use the IPv4 Address regex in Python?

Yes. import re pattern = re.compile(r'^((25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)$') bool(pattern.match("192.168.1.1")) # True