HTTP API

One domain with no account through POST /api/lookup, and the SVG badge at GET /api/badge/{domain}.

Two endpoints, both usable with no account.

POST /api/lookup

One domain, no account, 10 requests a minute per IP.

curl -s https://domduck.com/api/lookup \
  -H "content-type: application/json" \
  -d '{"domain":"stripe.com"}'

{
  "domain": "stripe.com",
  "domainRating": 95,
  "fetchedAt": "2026-08-03T06:59:19.000Z",
  "rank": 236,
  "backfilled": 0,
  "registration": {
    "registeredAt": "1995-09-12T04:00:00Z",
    "ageDays": 11283,
    "registrar": "SafeNames Ltd."
  },
  "tls": { "valid": true, "issuer": "DigiCert Inc", "daysRemaining": 101 },
  "series": {
    "dr": [{ "t": "2026-08-03", "v": 95 }],
    "rank": [{ "t": "2026-07-28", "v": 236 }]
  }
}

This is the one endpoint that may go upstream. It answers from the store when the stored Domain Rating is under twelve hours old, and fetches only on a miss. Everything else Domduck exposes reads the store and nothing else.

Deliberately one domain per request. A bulk lookup is an account feature.

Field	Notes
`domainRating`	Ahrefs Domain Rating, 0-100, higher is better.
`rank`	Tranco rank inside the top 1M. Lower is better. `null` outside it.
`backfilled`	Rank points written on this call. `0` on a cached answer, because nothing was written.
`registration`, `tls`	Best effort. `null` when a slow registry or a failed handshake would otherwise have cost you the rating.
`series`	Up to 90 days, oldest first, one point per reading. `v` may be `null`.

Failures: 400 for something that is not a domain, 429 when you or the upstream are rate limited, 502 when no rating could be read.

GET /api/badge/{domain}

An SVG badge for embedding on another site.

<a href="https://domduck.com/domain/stripe.com?utm_source=example.com" target="_blank">
  <img src="https://domduck.com/api/badge/stripe.com"
       alt="Monitor your Domain Rating with Domduck"
       width="138" height="24">
</a>

The badge never talks to Ahrefs. It reads Domduck's store, so a domain nobody has looked up renders a dash rather than triggering a fetch.

Height is always 24. Width is computed from the text: 135 for a one-digit rating, 138 for two digits, 147 for 100, 135 for an unknown domain. Two digits is almost everything, which is why the snippet says 138. An img whose attributes disagree with the SVG scales rather than crops, so if you generate the snippet, generate the width too, or omit both attributes and accept the layout shift.

What is not here

There is no bulk endpoint and no domain list endpoint, on purpose. An open endpoint that returns a rating for any name you hand it is a free dataset, and the Ahrefs licence Domduck reads Domain Rating under forbids compiling one. Every public surface reads what a real person already asked for.