Map the login dependency before you rely on or remove it
A “Continue with Google” or “Sign in with Apple” button can reduce the number of passwords you manage, but it also makes the companion-app account depend on a relationship between an identity provider and the app. That relationship is not the same as permission to read optional account data, an active app session, the app's own stored conversations, or account deletion. Draw a dependency triangle with the identity provider, the companion app, and the recovery mailbox or trusted device. Then complete a before-disconnect matrix: how you sign in now, which identifier the app uses, whether another login exists, what optional data access was granted, which sessions remain, and what the app says will happen after unlinking. The main risk is not “third parties” in general; it is losing track of which party controls each step.
Separate authentication from optional data access
Federated sign-in lets an identity provider send an identity or authentication assertion to a relying app. NIST SP 800-63C describes these as distinct roles in a federation. The app may receive a stable identifier and selected attributes needed to establish the account. A neighboring consent screen can also request authorization to access other data, but authorization and authentication are not interchangeable. RFC 9700 addresses protections around OAuth authorization flows, clients, redirects and tokens. For a consumer audit, record separate rows for sign-in identity, basic attributes, optional data grants, account linking and app sessions. Do not infer that a login button grants every permission, or that revoking one permission destroys the login relationship.
Check the identifier and duplicate-account boundary
Write down which identifier the companion app displays: an email address, a private relay address, a provider-specific account label, or something else. Do not publish the identifier in your checklist. If you previously registered with a password and later choose a provider button, confirm through current app documentation whether it links the same account or creates another one. Similar email text does not prove the records are merged. A duplicate can leave purchases, saved conversations, settings or deletion controls split between accounts. Test only with your own account and stop before confirming a merge you do not understand. If support is needed, use the developer contact shown in the official app listing and provide non-sensitive account references rather than conversation content.
Audit the dependency triangle and recovery chain
The identity-provider account may itself depend on a mailbox, phone, authenticator, security key or trusted device. The companion app can have a separate recovery or support path. Record which route restores the provider, which route restores the app, and which devices currently hold sessions. Consider ordinary events: changing the provider email, losing a trusted device, closing a mailbox, an organization-managed identity ending, or the provider sign-in being temporarily unavailable. The practical response is redundancy you have verified, not a prediction about outages. If the app offers an independent password or another sign-in method, add it only from a trusted signed-in session, confirm it works, and keep recovery secrets out of chats and ordinary notes.
Use a before-disconnect matrix
Before removing a connection, fill five rows: verified alternative sign-in, current provider identifier, optional data permissions, active app sessions, and app-owned data or subscription. Google's current help distinguishes Sign in with Google, linked accounts and access to Google Account data, and states that removing a connection does not delete data already held by the other service. Apple similarly lets users inspect apps using Sign in with Apple and stop using that connection, while later app access depends on the app. Therefore, do not use a provider's disconnect button as a substitute for the companion app's deletion, export, subscription or session controls. Capture only setting names and dates, not tokens, codes or private content.
Disconnect in a recoverable order and verify the result
First confirm a working alternative login or obtain the app's documented account-transition instructions. Next export only what you need through an official route and review subscriptions separately. Sign out obsolete companion-app sessions, then change or remove the provider connection from the documented screen. Reopen the app in a fresh browser profile or another device you control and test the intended login path. Check whether the old button is refused, whether an existing app session continues, and whether the same account—not an empty duplicate—opens. If you intend to leave entirely, use the app's account-deletion process as its own step. Record observed results and unresolved cells; do not repeatedly attempt unknown account-link operations.
Choose based on control ownership, not a universal winner
Third-party login may be practical when the provider account is well maintained, its recovery route is stable, the app explains account linking, and an alternative transition is available. A separate app password may be preferable when you want less dependency on one provider, but it adds another credential and recovery path to maintain. Neither option automatically determines how the app stores conversations or shares data. Review those in the app's privacy and data-sharing controls. Revisit the triangle after changing the provider account, recovery address, managed organization, main device or app login method. A short event-based review is more useful than assuming every external identity service is identical or continually checking it without a trigger.
Common questions
Does disconnecting third-party login delete my companion-app account?
Usually these are separate actions. Verify the app's own deletion process and the provider's current connection description.
Is signing in with a provider the same as granting access to all provider data?
No. Authentication and optional data authorization are separate rows, even if one interface presents both.
What should I do before stopping a provider login?
Verify an alternative sign-in or documented transition, identify the exact app account, review sessions and data controls, then test the result.