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Lesson 2 of 3 · Cross-platform identity

How identity works

This is the map, not the manual. By the end you'll be able to answer three questions: which tier you are, whether cross-platform stitching applies to you, and the one rule that makes it work.

3 min Concepts

When you're done: you can name your tier and know whether you need to do anything to make identity follow your users.

1 The anchor rule

Crossdeck binds a person to the most durable anchor you provide

Everything about identity follows from one idea: Crossdeck attaches a person to the most durable anchor your setup gives it — an anonymous handle, a Stripe customer, or your own app's user ID. The more durable the anchor, the more Crossdeck can do. So where you sit isn't a setting you pick; it's a consequence of what your app already has.

2 The three tiers

Find yourself on the ladder

There are three tiers, climbing from least to most durable. Most apps know their tier in one read:

  • Tier 1 — no backend, no payment. Anonymous visitors, journey analytics only. There's no money and no entitlements, so there's no durable identity to anchor to and nothing to stitch. You read what people did; you don't carry who they are.
  • Tier 2 — Stripe, no backend. The Stripe customer is the anchor; revenue is tracked against them. It's a single surface, so there's no cross-platform stitch — because there's no app identity to bridge to. This is a complete, valid mode, not a degraded one.
  • Tier 3 — backend present. Your authenticated app UID is the anchor — the passport. Identity persists across web and iOS, the Stripe subscription attaches to the UID, and entitlements follow the human across platforms. This is the only tier where stitching applies.
3 The cross-platform stitch & the one rule

The same UID on web and mobile is the same human

On Tier 3, the whole mechanism is this: you hand Crossdeck the same UID on web and on mobile. The web subscription attaches to that UID; the mobile install's anonymous handle aliases into it — so Pro resolves on the phone too. You assert the identity; Crossdeck doesn't guess, fingerprint, or match on email.

And the one rule that makes it work, the one to never get wrong:

  • The UID is what stitches — never the email. Apple Private Relay alone guarantees the iOS email won't match the web one, so email can't be the key.
  • The device handle is throwaway. The SDK-minted handle is anonymous — it gets attached to the UID; it is not the identity.
  • Skip identify() in the mobile app and your paying web customer sees free. That's the failure this rule prevents.
4 Which way from here

You know your tier — now you know what to do

If you're Tier 1 or Tier 2, you're done — cross-platform identity doesn't apply to you, and that's fine. If you're Tier 3 with real accounts on web and mobile, there's exactly one thing to do: call identify() with the same UID on both platforms. The next lesson wires that to your auth provider.

app.cross-deck.com · people
one person, two platforms

On Tier 3, user_847 is one record — web subscription attached, mobile handle aliased in, Pro live on both. The UID is the passport.

Next: wire your auth provider

Crossdeck anchors to the most durable thing you provide. Tier 1 and 2 have nothing to stitch. Tier 3's anchor is your app UID — and the one rule is that the same UID on web and mobile is the same human. Never email, never the device handle. Next, you wire it.