Fingerprint

A fingerprint is a compact, deterministic identifier derived by hashing a set of attributes that together describe something uniquely. The same inputs always produce the same fingerprint; different inputs produce a different one.

In the context of HTTP request idempotency, a request fingerprint is computed from the method, route, query string, payload, and content type. It is stored alongside the idempotency key so that retried requests carrying the same key but a different payload can be detected and rejected.

More broadly, fingerprinting is used for cache keying, change detection, file integrity checks, and browser device identification.

<?php

$fingerprint = hash('sha256', implode('|', [
    $request->method(),
    $request->path(),
    $request->getQueryString() ?? '',
    $request->getContent(),
    $request->header('Content-Type', ''),
]));

?>

See also How to generate a browser fingerprint with PHP.

Related : hash() Function, Idempotent, Deduplication, Cache, Checksum, Payload