Hostname Validator

Validate hostnames and domain names for proper syntax, length, and character compliance with RFC standards.

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About This Tool

This hostname validator tool allows you to check if domain names, hostnames, and URLs are valid according to internet standards (RFC 1123, RFC 952). It validates syntax, length restrictions, allowed characters, label structure, and top-level domain (TLD) validity. The tool provides detailed feedback on what's wrong with invalid hostnames and offers suggestions for correction. Perfect for developers, system administrators, and anyone working with domain registration or network configuration.

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How to Use

Enter a hostname, domain name, or URL in the input field
Select validation options (strict RFC 952 mode or modern RFC 1123 mode)
Click the 'Validate Hostname' button
View detailed validation results including syntax checks, length validation, character validation, and TLD verification
For invalid hostnames, see specific error messages and suggested corrections

Frequently Asked Questions

Find Quick Answers

What standards does this hostname validator follow?

The tool validates against RFC 1123 (modern standard) by default, with an option for strict RFC 952 validation. It checks hostname length (max 253 characters), label length (max 63 characters), allowed characters (letters, digits, hyphens), label start/end rules, and TLD validity.

Does this tool check if a domain is actually registered?

No, this is a syntax validator only. It checks if a hostname follows the proper format standards, but does not verify domain registration, DNS records, or website availability. For that, you would need a domain availability checker tool.

What's the difference between RFC 952 and RFC 1123 validation?

RFC 952 is the original 1985 standard that only allows letters, digits, and hyphens (no underscores). RFC 1123 (1989) is more permissive, allowing hostnames to start/end with digits and be more flexible. Most modern systems use RFC 1123, but some legacy systems may require RFC 952 compliance.

Can I validate URLs with this tool?

Yes, the tool automatically extracts the hostname portion from URLs (removing http://, https://, and paths). Just paste a full URL and it will validate the domain/hostname part.

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