Multi-accounting: recognise one person behind many accounts

The threat

The second account is usually made in another browser, on a phone, or in your app. A system that only compares email addresses sees five customers.

What we stop

• Another claim from the same device, or from another browser on the same computer and network.
• Claims from devices on the same home network, including a phone that was on the home Wi-Fi and now uses mobile data.
• Claims split between your website and your apps, when the projects share a claim group.

Found later, flagged

A device that claimed before anything tied it to a household is flagged when it later shows up on that network. Your backend polls for flags and decides what to do. Nothing is revoked automatically, because shared networks such as an office or a café also exist and the call is yours.

Poll for related claims

let after = lastSeenFlagId; // store the last flagId you processed
for (;;) {
  const url = `https://api.fpchecker.com/v1/claims/flags?limit=100${after ? `&after=${after}` : ''}`;
  const r = await (await fetch(url, { headers: { 'X-Secret-Key': process.env.FPCHECKER_SECRET_KEY } })).json();
  if (!r.ok) throw new Error(r.reason); // never read an error as "nothing flagged"
  for (const f of r.flags) await reviewClaim(f.claimId, f.relatedClaimId, f.kind, f.reason); // your code
  if (!r.next) break;
  after = r.next;
}

Frequently asked questions