What is hashed email matching?

The rule is fixed and public: trim the address, lowercase it, take the SHA-256 hash, and write it as 64 lowercase hex characters. The same address always produces the same hash, so hashes from different sources match; but a hash cannot be turned back into the address.

CoverClicks only ever stores and matches hashes. A buyer uploads hashes (or lets a connected ATS send emails that are hashed in memory the instant they arrive and discarded). Publishers send hashes from their own pages. Every signal returned is keyed by the hash plus the buyer's own record id, so the buyer resolves it to a person on their own side.

Hashing is not anonymization on its own, which is why the signals returned are deliberately coarse: no site names, no visit dates, no job titles viewed. The buyer learns that a person it already knows is active and roughly how, nothing more.

Does it handle Gmail dots and plus addresses?

No. The rule hashes the address as written, with only trimming and lowercasing, so that every party produces identical hashes. Normalize on your side if you want to.

Can I send plain emails instead?

A connected ATS sends them to our server, where they are hashed before anything is stored. File uploads accept an email column and hash it on arrival the same way. The address is never written to disk.

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