Idna domain diagnose

idna-domain-diagnose · version 1.0.0 · URLs & IP addresses · free, no key needed

Validate each dot-separated IDNA2008 label and the 253-octet DNS wire length.

Use when you need to: diagnose an idna2008 domain · check every label in a domain name · idna domain wire octet length.

Decide before calling

Read the versioned contract and the supported scope below. Reuse idna-domain-diagnose@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use idna-domain-diagnose@1.0.0 for diagnose an idna2008 domain. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• diagnose an idna2008 domain
• check every label in a domain name
• idna domain wire octet length
• trailing dot fully qualified domain check
• registration profile for a whole domain
• which label breaks this idna domain
• אבחון שם מתחם לפי תוויות

Not supported

• resolve DNS records for this name
• convert the name with UTS 46 mapping
• treat ideographic full stops as label separators

Behavior

• The domain is split only on U+002E FULL STOP. Every other dot stays inside a label and is judged there.
• One trailing U+002E is a fully-qualified marker: trailing_dot is true and it is not an empty label. A domain that is only that dot is empty_domain.
• Each remaining label uses idna-label-validate rules: registration rejects a non-lowercase A-label as alabel_not_lowercase, while lookup may lowercase it. An empty label between dots is empty_label.
• The first invalid label sets reason, reason_label, reason_index, and cp. wire is null when any label is invalid.
• When every label is valid, wire is the ASCII alabels joined by dots, excluding a stripped trailing dot. Longer than 253 octets is dns_domain_length. wire is still returned when it fits in 4096 characters.
• There is no extra whole-domain Bidi Rule. No DNS query is performed. Results are not a homograph, phishing, or authenticity verdict.
• A domain over 1023 bytes, a label over 252 bytes, or more than 127 labels is limit_exceeded rather than valid:false.

Input

• domain (string, required): min length 1; max length 1023
• profile (one of "registration", "lookup", required)

Output

• valid (boolean, required)
• reason (one of null, "disallowed", "unassigned", "contextj", "contexto", "not_nfc", "leading_combining_mark", "hyphen_position", "bidi_rule", "punycode_decode", "punycode_roundtrip", "alabel_not_lowercase", "punycode_encode", "ace_all_ascii", "dns_label_length", "not_ldh", "empty_label", "empty_domain", "dns_domain_length", required)
• reason_label (integer or null, required): min 0; max 126
• reason_index (integer or null, required): min 0; max 251
• cp (integer or null, required): min 0; max 1114111
• trailing_dot (boolean, required)
• label_count (integer, required): min 0; max 127
• wire (string or null, required): min length 1; max length 4096
• labels (array of object, required): max items 127
• data_version (constant "idna2008-rfc5892-unicode-15.1.0", required)

Limits

• max domain bytes: 1023
• max label bytes: 252
• max labels: 127
• max output bytes: 65536

Example

Request input:

{
  "domain": "a.",
  "profile": "lookup"
}

Response:

{
  "result": {
    "valid": true,
    "reason": null,
    "reason_label": null,
    "reason_index": null,
    "cp": null,
    "trailing_dot": true,
    "label_count": 1,
    "wire": "a",
    "labels": [
      {
        "label": "a",
        "valid": true,
        "reason": null,
        "reason_index": null,
        "cp": null,
        "form": "nr-ldh",
        "ulabel": "a",
        "alabel": "a",
        "direction": "none",
        "bidi_condition": null
      }
    ],
    "data_version": "idna2008-rfc5892-unicode-15.1.0"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "idna-domain-diagnose",
  "version": "1.0.0",
  "input": {
    "domain": "a.",
    "profile": "lookup"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/idna-domain-diagnose/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"domain":"a.","profile":"lookup"}'

The machine-readable contract is at /v1/tools/idna-domain-diagnose/versions/1.0.0.

CLI

node cli.mjs run idna-domain-diagnose 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Idna label validate: Validate one already-mapped IDNA2008 label for registration or lookup.
• Idna domain to ascii: Convert a domain to DNS ASCII with UTS #46 ToASCII, STD3, and DNS lengths.
• Idna domain map: Map a domain with the Unicode 17 UTS #46 table, steps 1 and 2 only.
• Idna domain to unicode: Convert a domain to Unicode with UTS #46 ToUnicode and decode A-labels.
• IPv4 prefix set subtract: Subtract one IPv4 prefix set from another into sorted minimal disjoint CIDRs.
• IPv4 in CIDR: Test whether a canonical IPv4 address lies in a CIDR prefix whose host bits are zero.