SignupSieve API docs

Catch fake signups, not just bad emails.

SignupSieve tells you whether a real, unique person is behind an email address. One call returns:

a human_score from 0 to 100,
a verdict: allow, review or block,
the reasons behind it.

It never contacts mail servers, answers in milliseconds, and learns from the outcomes you report.

Get an API key

Open SignupSieve on RapidAPI and sign in (free).
Subscribe to the Basic plan: 1,000 checks a month, no card needed.
Copy your key and host from the Code Snippets panel.

Keep your RapidAPI key on your server. Never put it in browser or mobile app code.

Quick start (first call in 2 minutes)

Send the address in a POST body. Add the user's IP if you have it; this is optional but catches more bots.

curl -X POST "https://signupsieve.p.rapidapi.com/v1/check" \
  -H "Content-Type: application/json" \
  -H "X-RapidAPI-Key: YOUR_RAPIDAPI_KEY" \
  -H "X-RapidAPI-Host: signupsieve.p.rapidapi.com" \
  -d '{"email": "maria.santos@gmail.com", "ip": "203.177.10.10"}'

{
  "email": "maria.santos@gmail.com",
  "canonical": "mariasantos@gmail.com",
  "account_type": "free",
  "role_account": false,
  "disposable": false,
  "relay": false,
  "deliverable_domain": true,
  "mail_provider": "google",
  "human_score": 94,
  "verdict": "allow",
  "reasons": ["natural_name", "dotted_gmail"],
  "ip": { "tor": false, "signups_from_ip": 1 },
  "check_id": "chk_AXDmekmC35NL1mpGtCtC...",
  "model": "baseline"
}

Use the exact host and key shown in the Code Snippets panel on our RapidAPI listing. The host above is an example.

Privacy

Email and IP addresses are analyzed, then forgotten. Never stored, never sold.
We never send email or contact mail servers, so checks are silent and your IP is never blacklisted.
We store only domain-level data (mail servers, outcome counts) and one-way hashes that cannot be turned back into addresses.
For labelled checks, we store the signal numbers and the outcome, not the address.
To allow feedback by email, we keep your latest check of each inbox for 14 days, under a one-way hash of the address.

Next steps

Use the verdict: what to do with allow, review and block.
Endpoints: single, bulk, feedback and model stats.
Code examples: Node.js, Python, PHP, Next.js, Express and Laravel.
Pricing: from $0 a month.
Download the OpenAPI spec or the Postman collection.