Validate domain

Check a domain name’s ASCII labels and DNS length limits.

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ToolDomain Validator
Input
Output
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Preview

How it works

The lowercased value is split at dots, checked against 253-character whole-name and 63-character label limits, and each label must start and end with a letter or digit while allowing internal hyphens. A two-label minimum is required by this check.

  • The 63/253 limits follow DNS constraints.
  • Lowercasing makes the result stable for case-insensitive names.

Worked example

Valid Domain
Validate a standard domain name
Input
											example.com
Output
												Valid domain: example.com

When to use this

DNS editors, TLS requests, and web-crawler input checks validate domains.

Edge cases

  • Underscores are rejected even though some service-discovery names use them.
  • A trailing fully qualified-name dot is rejected by this presentation rule.
  • Raw Unicode IDNs need punycode normalization before ASCII validation.

References