The short answer to 'is Sign in with Apple private?' is: it is more privacy-preserving than many login flows, but it is not invisibility. Apple's design can hide your actual email address with a relay address, and that is a real improvement over handing every merchant the same inbox. It also gives you a way to avoid password reuse on a new shopping site. But the merchant still gets a stable account relationship, and that relationship is often enough to link orders, support tickets, returns, and marketing messages over time.
That matters because login is not just authentication. It is a data handoff. When a shopper signs in, the site can attach purchases, wish lists, shipping details, saved payment methods, device signals, and customer support history to one profile. Apple's own material frames Sign in with Apple as a way to keep your Apple ID private while sharing what is necessary to create an account. The privacy win is real, but the login still turns a one-time visit into a durable identity path that merchants can use again later.
Apple's Hide My Email feature reduces address exposure, but it does not erase the account itself. A forwarding alias can keep your primary inbox out of the merchant's database, which helps if that retailer gets breached or sold data to a marketing vendor. Yet the alias still routes to you, the merchant still knows the alias belongs to a repeat shopper, and the account can still accumulate behavioral history. For shopping, that means the question is not whether the email is hidden. The question is what else the retailer learns once the login is accepted.
The FTC's guidance on protecting personal information is useful here because it reminds businesses to limit collection, control access, and dispose of data when it is no longer needed. A login provider should not turn a simple account creation step into a broad profiling package. If a merchant only needs a receipt channel, it should not demand a phone number, birthday, or the user's main inbox on top of the Apple relay. If a site can let someone check out as a guest, it should also explain why an account is required at all.
NIST's federation guidance helps explain the deeper tradeoff. Federation can make sign-in easier and safer, but it also centralizes identity at the account provider. That can be good for security and bad for over-linking if the same identity handle gets reused everywhere. A shopper who uses Sign in with Apple across many merchants may reduce password fatigue but also create a wide trail of linked accounts that are easy for the stores to recognize as belonging to the same person, even if each store only sees the relay address.
The practical shopper rule is simple: use Sign in with Apple when you want a cleaner address trail and stronger password hygiene, but do not treat it like a disposable guest pass. For low-stakes purchases, guest checkout may still be the better privacy choice. For repeat accounts that need receipts, returns, or warranty access, Sign in with Apple can be a reasonable compromise if you understand the tradeoff: less email exposure, more account durability. That is a good defense, but it is still a profile.
cloak should read this as a login-risk signal, not just a convenience feature. If a site steers you toward account creation while also asking for unnecessary profile fields, it is using the promise of privacy to encourage a long-lived identity. The anti-exploitation stance is to make that tradeoff visible: masked email yes, unnecessary identity expansion no. Shopping should not require handing every merchant a permanent handle on your future behavior just to see the total.
There is also a recovery-story angle that users often miss. Even when the merchant only sees a relay address, the account may still be recoverable through the upstream Apple identity and whatever trust signals the platform uses to verify ownership. That is good for account rescue but bad if you expected a throwaway shopping alias. If the merchant offers account deletion, ask whether the removal covers profile history, billing records, support transcripts, and marketing segments, not just the visible login name.