IP Address Regex Javascript Validator

IP Address Regex JavaScript Validator

What is IP Address Regex?

An IP address is a unique string that identifies a device on a network. It comes in two forms: IPv4 and IPv6. Validating IP addresses using regular expressions (regex) in JavaScript helps ensure accurate and secure input for forms, APIs, and configuration settings.

Regex is especially useful in frontend validation where preventing malformed IP entries can reduce backend errors and security issues.

What is the Bit Size of an IPv4 Address?

An IPv4 address is made up of 32 bits. These bits are typically displayed as four decimal numbers (ranging from 0 to 255), separated by dots—for example, 192.168.0.1. Each number corresponds to 8 bits, often called an "octet," making IPv4 addresses both compact and easy to represent in text form. This 32-bit structure enables approximately 4.3 billion unique addresses, which is the main reason for the eventual shift toward IPv6 as the internet expanded.

Regex Patterns for IP Address Validation

1. IPv4 Address

IPv4 consists of four groups of 1 to 3 digits (0–255), separated by dots. This means IPv4 addresses occupy the range from to , covering the full spectrum of possible values for each segment.

Common Regex Syntax Cheatsheet
In regular expressions, certain syntax elements have specific meanings. Square brackets [] are used to match any character inside them. The symbol \d matches any single digit. The + symbol means one or more of the preceding element, * means zero or more, and ? indicates that the preceding element is optional (zero or one occurrence). The caret ^ represents the start of a string, while the dollar sign $ represents the end. For example, the expression (hello)+ would match the string "hellohellohellohello". If you want to match a literal dot character, you use \. instead of just . which matches any character.

Regex Pattern (IPv4):

^((25[0-5]|2[0-4]\d|1\d{2}|[1-9]?\d)\.){3}(25[0-5]|2[0-4]\d|1\d{2}|[1-9]?\d

Matches: 192.168.1.1, 127.0.0.1, 255.255.255.255

Invalid: 300.168.1.1, 192.168.1, abcd.123.0.1

2. IPv6 Address

IPv6 is a longer hexadecimal-based format, typically written in 8 groups separated by colons.

Regex Pattern (IPv6 - simplified):

^([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}$

Matches: 2001:0db8:85a3:0000:0000:8a2e:0370:7334

Invalid: 2001:db8:85a3::8a2e:370g:7334

⚠️ Note: There are more advanced patterns to match IPv6 shorthand and mixed forms; the above works for the full, expanded format.

Use these regex patterns as building blocks for your validation logic, and refer back to the cheatsheet above for quick reminders on core regex components. This foundation helps ensure your IP address validation is both accurate and maintainable.

How to Validate IP Address in JavaScript Using Regex

function isValidIPv4(ip) {
  const ipv4Regex = /^((25[0-5]|2[0-4]\d|1\d{2}|[1-9]?\d)\.){3}(25[0-5]|2[0-4]\d|1\d{2}|[1-9]?\d)$/;
  return ipv4Regex.test(ip);
}

function isValidIPv6(ip) {
  const ipv6Regex = /^([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}$/;
  return ipv6Regex.test(ip);
}

// Example usage
console.log(isValidIPv4("192.168.0.1"));    // true
console.log(isValidIPv6("2001:0db8:85a3:0000:0000:8a2e:0370:7334")); // true

Use Cases

• Web Forms: Validate IP address inputs before submission.

• Network Monitoring Apps: Match valid device IPs using JavaScript Regex Tester.

• APIs and Admin Panels: Ensure safe backend routing or configuration using validated IPs.

• Log Analysis: Extract IP addresses from server logs using the String Extractor.

Pro Tips

• Always use anchors (^ and $) to ensure the entire string matches the pattern.

• IPv6 has many valid shorthand notations; if you need to support them, consider libraries or advanced regex.

• Use trim() on inputs before testing to avoid whitespace mismatches.

• For bulk validation or testing multiple formats, combine this tool with the JavaScript Regex Tester.