feature request: How to implement anonymous user login?

[a523]

What problem did you meet?

How to implement anonymous user login?
My product aims to provide unregistered users with a trial option, which typically requires the backend to generate an anonymous user.
I'm not sure how Logto achieves this.

Describe what you'd like Logto to have

support anonymous user login

[xiaoyijun]

Hi @a523 , Logto currently doesn’t provide a built-in “anonymous user / anonymous login” flow (i.e., obtaining an OIDC session/token without user interaction). However, you can achieve the same “guest → registered user” experience by handling the guest identity in your application backend and merging data after the user signs up/signs in.

The flow may look like this:

sequenceDiagram
  autonumber
  participant U as User
  participant FE as Frontend (App)
  participant BE as Your Backend
  participant L as Logto (OIDC)

  Note over FE,BE: Guest phase (no Logto user yet)
  U->>FE: Use app without signing up
  FE->>BE: POST /guest (or /session)
  BE-->>FE: guestId (set-cookie / jwt / localStorage)
  FE->>BE: Use guestId to save draft/cart/etc.
  BE-->>FE: OK (data stored under guestId)

  Note over FE,L: Sign-up / Sign-in phase (OIDC)
  U->>FE: Click "Sign up / Sign in"
  FE->>L: OIDC authorize (redirect)
  L-->>FE: Redirect back with code
  FE->>BE: Exchange code (backend) / validate tokens
  BE-->>FE: Logged-in session (userId/sub available)

  Note over FE,BE: Merge phase (business-owned)
  FE->>BE: POST /merge-guest { guestId }
  BE->>BE: Merge guest data -> userId (sub)
  BE-->>FE: 200 OK (guest merged & invalidated)

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