Private attributes

Mark attributes as private so they're used for targeting but never persisted or sent to the events store.

Production readyOn this page · 3 min readUpdated · June 19, 2026Works with · @shipeasy/sdk · server + client

Some attributes you target on are sensitive — an email, a customer tier, a national ID. You still want to evaluate against them (target email endsWith "@acme.com"), but you don't want them leaving the process or landing in the events store. privateAttributes does exactly that.

Declare them once

privateAttributes is an Engine construction option — list the attribute names when you build the engine (or pass them to configure(...), which builds the shared engine for the bound-client flow). They're used locally for evaluation and stripped from every event the SDK emits:

import { configure } from "@shipeasy/sdk/server";

configure({
  apiKey: process.env.SHIPEASY_SERVER_KEY!,
  attributes: (u) => ({ user_id: u.id, email: u.email, plan: u.plan }),
  privateAttributes: ["email", "ssn"],
});

// signature
privateAttributes?: string[];

The same option is available when you construct an Engine directly:

import { Engine } from "@shipeasy/sdk/server";

const engine = new Engine({
  apiKey: process.env.SHIPEASY_SERVER_KEY!,
  privateAttributes: ["email", "ssn"],
});

Now a rule can target email, but email and ssn are removed before any exposure or track event is sent to /collect. With the bound flow, the attributes come from your transform:

const flags = new Client(currentUser); // email is in the attribute map…
flags.getFlag("beta_program");
// …used for targeting, but never serialized into the exposure event

Evaluate locally, transmit nothing

Evaluation runs in your process against the in-memory rule set, so a private attribute never has to travel anywhere to be targeted on. Private attributes only ever affect what the SDK sends — the matching itself is unchanged.

What stays and what goes

	Targeting / evaluation	Sent to events store
Normal attribute	✅ used	✅ included
Private attribute	✅ used	❌ stripped

Use it for anything you wouldn't want in analytics: PII, billing identifiers, security-sensitive flags.

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