Network & Web · In-Browser Regular Expression Lab

IPv4 Regex — Validate 0-255 Decimal Octets with CIDR Support

Strictly validates IPv4 addresses ensuring each octet is within the valid 0 to 255 numerical range.

Pattern:

Regular Expression Pattern & Flags

Flags:

//none

Live Test String

Match Found

Load Sample:

Match Inspection & Details1 match

Match #1:192.168.1.1

Test Samples Verification Matrix

Expected Valid Samples (Should Match)

192.168.1.1 Pass

10.0.0.254 Pass

127.0.0.1 Pass

255.255.255.0 Pass

Expected Invalid Samples (Must Reject)

256.1.1.1 Rejected (Pass)

192.168.1 Rejected (Pass)

192.168.1.1.1 Rejected (Pass)

1.2.3.999 Rejected (Pass)

Code Implementation Generator

// JavaScript / TypeScript (ES6+)
const pattern = /^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/;
const text = "192.168.1.1";

const isMatch = pattern.test(text);
console.log("Is Match:", isMatch);

if (isMatch) {
  const matches = text.match(pattern);
  console.log("Matches:", matches);
}

Regular Expression Token Breakdown

Checks four dot-separated octets ensuring numbers never exceed 255. Each component of the regular expression serves a distinct syntactical purpose as mapped below:

Token Pattern	Name / Component	Function & Rule
25[0-5]	Range 250-255	Matches 250 to 255.
2[0-4][0-9]	Range 200-249	Matches 200 to 249.
[01]?[0-9][0-9]?	Range 0-199	Matches 0 to 199.
\.	Dot delimiter	Matches period separating octets.
{3}	Repeat 3 times	Repeats octet and dot for the first 3 groups.