@walkeros/server-transformer-fingerprint

Server-side user identification for walkerOS without cookies. Hashes configurable request fields into a deterministic identifier and stores it on the event. No cookies, no PII stored: the same inputs always produce the same hash, which gives session continuity and cross-domain stitching without a client-side ID.

Documentation • NPM Package • Source Code

Installation

npm install @walkeros/server-transformer-fingerprint

Quick start

import { startFlow } from '@walkeros/collector';
import { transformerFingerprint } from '@walkeros/server-transformer-fingerprint';

await startFlow({
  transformers: {
    fingerprint: {
      code: transformerFingerprint,
      config: {
        settings: {
          fields: ['ingest.ip', 'ingest.userAgent'],
          output: 'user.hash',
          length: 16,
        },
      },
    },
  },
});

The event then carries the hash at the configured output path:

{ "name": "page view", "user": { "hash": "158f99cc06e33fd6" } }

Fields resolve from { event, ingest } using walkerOS mapping. Strings use dot notation, and function values compute dynamically. A missing field is treated as an empty string, and the transformer never throws.

Daily rotation

Without rotation the same IP and user agent produce the same hash indefinitely. Add a date field to reset it each day, which limits cross-day tracking while keeping session continuity within a day:

settings: {
  fields: [
    'ingest.ip',
    'ingest.userAgent',
    { fn: () => new Date().toISOString().slice(0, 10) },
  ],
  output: 'user.hash',
  length: 16,
}

Documentation

Full configuration, IP anonymization, and examples live in the docs: https://www.walkeros.io/docs/transformers/fingerprint

Contribute

Feel free to contribute by submitting an issue, starting a discussion, or getting in contact.

License

MIT