> ## Documentation Index
> Fetch the complete documentation index at: https://docs.meridian.study/llms.txt
> Use this file to discover all available pages before exploring further.

# Event Check-in & Anonymous Identifiers

> Check-in system, anonymous registration, and identifier handling for events

# Event Check-in & Anonymous Identifiers

This document describes the event check-in system, anonymous registration flows, and how anonymous identifiers are used across the platform.

## Check-in System Overview

The check-in system supports three primary flows:

<CardGroup cols={3}>
  <Card title="Logged-in self check-in" icon="user-check">
    Users with accounts check in from the event page or via token link
  </Card>

  <Card title="Token-based check-in" icon="key">
    Anyone with a valid check-in token (QR code or link) can access check-in
  </Card>

  <Card title="Anonymous pick-your-registration" icon="user-circle">
    Unauthenticated users with a token search and select their registration to check in
  </Card>
</CardGroup>

### Check-in Settings

Events can configure check-in behavior via `checkInSettings`:

| Setting                 | Description                                                    |
| ----------------------- | -------------------------------------------------------------- |
| `allowEarlyCheckIn`     | Allow check-in before event start time                         |
| `allowAnonymousCheckIn` | Enable anonymous (FormResponse) registrations in check-in list |
| `allowOnPageCheckIn`    | Allow check-in from the event page (vs. token link only)       |
| `requireRegistration`   | Require registration before check-in (logged-in users)         |
| `autoCheckIn`           | Automatically check in when conditions are met                 |

### Check-in Token

Each event with check-in enabled has a `checkInToken` — a secret hex string used to gate check-in access. The token is:

* **Included in QR codes and check-in links** (e.g. `/check-in/:eventId/:token`)
* **Required for anonymous flows** — self-registrations and anonymous check-in endpoints validate the token
* **Not exposed** to unauthenticated users except via the check-in URL (e.g. from QR scan)

***

## Check-in Flows

### 1. Logged-in Self Check-in (no token)

**Route:** Event page → Check In button\
**Endpoint:** `POST /events/:eventId/check-in/self`\
**Auth:** Required (`verifyToken`)

* User must be logged in
* No token needed
* Uses `req.user.userId` to find/create attendee
* Validates event time and `requireRegistration` if set

### 2. Logged-in Token Check-in

**Route:** `/check-in/:eventId/:token`\
**Endpoint:** `POST /events/:eventId/check-in`\
**Body:** `{ token }`\
**Auth:** Optional (`verifyTokenOptional`)

* User is logged in and has the token in the URL
* Token validates access
* Same logic as self check-in but with token validation

### 3. Anonymous Pick-Your-Registration

**Route:** `/check-in/:eventId/:token` (user not logged in)\
**Endpoints:**

* `GET /events/:eventId/check-in/self-registrations?token=xxx` — list registrations
* `GET /events/:eventId/check-in/registration/:formResponseId?token=xxx` — form details
* `POST /events/:eventId/check-in/anonymous` — check in by `userId` or `formResponseId`\
  **Auth:** None (token validates)

Flow:

1. User opens check-in link (from QR or event page) with token
2. Frontend fetches registrations via `self-registrations`
3. User searches by name/email and selects their registration
4. User can "View details" to see their full registration form (anonymous only)
5. User clicks "Check In" → `POST /events/:eventId/check-in/anonymous` with `{ token, formResponseId }` or `{ token, userId }`

<Note>
  Anonymous check-in is **not** locked to the browser. Users can register on one device and check in on another — they only need the token and to find their name in the list.
</Note>

### 4. Manual Check-in (Organizer)

**Endpoints:**

* `POST /events/:eventId/check-in/:userId` — check in logged-in attendee
* `POST /events/:eventId/check-in/by-form-response/:responseId` — check in anonymous attendee

**Auth:** Required (`verifyToken`) + event management permission

Organizers use the Event Dashboard Check-in tab to search and manually check in attendees.

***

## Anonymous Registration

### FormResponse Model

Anonymous registrations are stored as `FormResponse` documents with `submittedBy: null`:

```javascript theme={null}
{
  form: ObjectId,
  event: ObjectId,
  formSnapshot: Object,  // Form as it was when submitted
  submittedBy: null,    // null = anonymous
  guestName: String,
  guestEmail: String,
  answers: [ ... ],
  submittedAt: Date
}
```

### Browser localStorage (anonymousRegistrationStorage)

The frontend uses `meridian-anonymous-registrations` in localStorage to track when the **current browser** has registered for an event without an account.

**Purpose:**

* Show "You are registered" on the event page
* Verify with server that registration still exists (`GET /events/:eventId/check-anonymous-registration?guestEmail=...`)
* Support "Add another registration" — allow multiple anonymous registrations per event from the same browser

**Storage shape:**

```javascript theme={null}
{
  [eventId]: {
    guestName: string,
    guestEmail: string,  // normalized (trim + lowercase)
    registeredAt: string,  // ISO date
    _v: number
  }
}
```

**Key functions:**

* `hasAnonymousRegistration(eventId)` — whether this browser has a stored registration
* `getAnonymousRegistration(eventId)` — get stored details
* `saveAnonymousRegistration(eventId, { guestName, guestEmail })` — save after successful registration
* `removeAnonymousRegistration(eventId)` — clear when server says registration no longer exists
* `getAllAnonymousRegistrations()` — for claim API

<Warning>
  localStorage is **browser-scoped**. It does not gate check-in. Users can check in from any device with the token — the list comes from the server, not localStorage.
</Warning>

### Claim Anonymous Registrations

When a user signs up or logs in, the frontend calls `POST /claim-anonymous-registrations` with `{ registrations: [ { eventId, guestEmail } ] }`. For each matching anonymous FormResponse (same event, `submittedBy: null`, email match), the backend:

1. Sets `submittedBy` to the user's ID
2. Updates `guestName`/`guestEmail` from the user account if the form collects them
3. Adds the user to `event.attendees` if not already present

This links previously anonymous registrations to the new account.

***

## Anonymous Identifiers (Analytics)

Separate from event registration, the **analytics platform** uses an `anonymous_id` for tracking events before and after login:

| Concept                       | Purpose                                                   | Storage                                  |
| ----------------------------- | --------------------------------------------------------- | ---------------------------------------- |
| **Analytics `anonymous_id`**  | Device-scoped persistent ID for analytics events (no PII) | Client (e.g. AsyncStorage, localStorage) |
| **Anonymous FormResponse**    | Event registration without account (`submittedBy: null`)  | Server (MongoDB)                         |
| **localStorage registration** | "This browser registered for this event"                  | Client (localStorage)                    |

See [Analytics Platform](/backend/analytics-platform) for the analytics envelope and `anonymous_id` usage.

***

## API Reference

### Public Check-in (token required, no auth)

| Method | Endpoint                                                           | Description                                                           |
| ------ | ------------------------------------------------------------------ | --------------------------------------------------------------------- |
| GET    | `/events/:eventId/check-in/self-registrations?token=xxx`           | List registrations (logged-in + anonymous) for pick-your-registration |
| GET    | `/events/:eventId/check-in/registration/:formResponseId?token=xxx` | Get form snapshot + answers for an anonymous registration             |
| POST   | `/events/:eventId/check-in/anonymous`                              | Check in by `{ token, formResponseId }` or `{ token, userId }`        |

### Authenticated Check-in

| Method | Endpoint                         | Description                         |
| ------ | -------------------------------- | ----------------------------------- |
| POST   | `/events/:eventId/check-in/self` | Self check-in (logged-in, no token) |
| POST   | `/events/:eventId/check-in`      | Token check-in (body: `{ token }`)  |
| POST   | `/events/:eventId/check-out`     | Remove own check-in                 |

### Organizer / Management

| Method | Endpoint                                                 | Description                 |
| ------ | -------------------------------------------------------- | --------------------------- |
| POST   | `/events/:eventId/check-in/enable`                       | Enable check-in             |
| POST   | `/events/:eventId/check-in/disable`                      | Disable check-in            |
| PUT    | `/events/:eventId/check-in/settings`                     | Update check-in settings    |
| GET    | `/events/:eventId/check-in/qr`                           | Get QR code for check-in    |
| GET    | `/events/:eventId/check-in/link`                         | Get check-in URL            |
| GET    | `/events/:eventId/check-in/attendees`                    | List checked-in attendees   |
| POST   | `/events/:eventId/check-in/:userId`                      | Manual check-in (logged-in) |
| POST   | `/events/:eventId/check-in/by-form-response/:responseId` | Manual check-in (anonymous) |

### Anonymous Registration Verification

| Method | Endpoint                                                       | Description                                                                                          |
| ------ | -------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------- |
| GET    | `/events/:eventId/check-anonymous-registration?guestEmail=xxx` | Check if anonymous registration exists (for localStorage sync)                                       |
| POST   | `/claim-anonymous-registrations`                               | Claim anonymous registrations after sign-up (body: `{ registrations: [ { eventId, guestEmail } ] }`) |

***

## Frontend Components

| Component                    | Location                                              | Purpose                                                                                    |
| ---------------------------- | ----------------------------------------------------- | ------------------------------------------------------------------------------------------ |
| `EventCheckInButton`         | `Meridian/frontend/src/components/EventCheckInButton` | Check-in button on event page; navigates with token for anonymous                          |
| `CheckInConfirmation`        | `Meridian/frontend/src/pages/CheckIn`                 | Check-in page; handles token validation, anonymous pick UI, form details modal             |
| `ManualCheckInModal`         | `Meridian/frontend/.../EventCheckInTab`               | Organizer manual check-in (search + select)                                                |
| `RSVPButton` / `RSVPSection` | `Meridian/frontend/src/components`                    | Registration; uses `anonymousRegistrationStorage` for "registered" state and "Add another" |

***

## Related pages

<CardGroup cols={2}>
  <Card title="Event dashboard" icon="table-columns" href="/atlas/event-dashboard">
    Event management, readiness, and organizer tooling around the same events.
  </Card>

  <Card title="Event management API" icon="calendar" href="/api-reference/event-management">
    REST paths for RSVPs, agendas, and org-event operations used by check-in flows.
  </Card>

  <Card title="Beacon events" icon="calendar" href="/beacon/events">
    Event lifecycle, approvals, and RSVP from the Beacon product lens.
  </Card>

  <Card title="Platform analytics" icon="chart-column" href="/backend/analytics-platform">
    Event pipeline, envelope schema, and `anonymous_id`–friendly tracking.
  </Card>

  <Card title="Analytics collected events" icon="list" href="/backend/analytics-collected-events">
    Named events and properties emitted by web and mobile clients.
  </Card>

  <Card title="Atlas messaging" icon="mail" href="/atlas/messaging">
    Announcements and anonymous recipients tied to event outreach.
  </Card>
</CardGroup>