Glossary
Salted visitor hash
An identifier computed on the server from a visitor’s address and browser, plus a value that changes, so that it expires by itself. Pseudonymous, not anonymous.
A salted visitor hash is an identifier a server computes from what each request already carries, usually the address and user agent, combined with the site and a changing value called a salt. Nothing is stored in the browser, and when the salt changes, the same person gets a new value.
In Trailic it’s sha256(salt, site, address, user agent), with a salt derived per UTC day from TRAILIC_SECRET. The address isn’t stored.
Its error goes both ways: people sharing an address and browser merge, and anyone who changes network or device counts twice. It also isn’t anonymisation, since whoever holds the secret and knows someone’s address and browser can compute their hash. The full walkthrough, with code, is in how to count visitors without cookies.