Guide · 6 min read ·
How to detect duplicate signups without blocking real users
A practical checklist for finding repeat accounts: mailbox normalization, device signals, network clustering and signup timing.
1. Normalize the mailbox
Lowercase the address, remove dots and plus tags for providers that ignore them, then compare. This alone catches many repeat trials.
2. Recognize the device
A device fingerprint links signups even after cookies are cleared. Identical hardware is common in offices, so combine it with network and time windows instead of merging people blindly.
3. Cluster by network
Several signups from the same /24 subnet in a short window is a useful but weak signal. Treat it as evidence for review, not proof.
4. Measure signup timing
Humans need time to read and type. A signup completed in a few seconds points to automation.
5. Explain every decision
Show which signals fired and how many points each added. Your team can then review borderline cases instead of guessing.
See how much farming costs you
Upload past signup emails and Unfarm groups the repeat accounts with a clear reason for each.
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