> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/supertokens/supertokens-core/llms.txt
> Use this file to discover all available pages before exploring further.

# Get User by ID

> Retrieve user information by user ID

## GET /user/id

Retrieve detailed information about a user by their user ID.

## Query Parameters

* **userId** (string, required): The user ID to retrieve. Can be either a SuperTokens user ID or an external user ID (if user ID mapping is configured)

## Response

### Success Response

```json theme={null}
{
  "status": "OK",
  "user": {
    "id": "string",
    "timeJoined": "number",
    "isPrimaryUser": "boolean",
    "emails": ["string"],
    "phoneNumbers": ["string"],
    "thirdParty": [],
    "loginMethods": [
      {
        "recipeId": "string",
        "recipeUserId": "string",
        "timeJoined": "number",
        "verified": "boolean",
        "email": "string (optional)",
        "phoneNumber": "string (optional)",
        "thirdParty": {
          "id": "string",
          "userId": "string"
        } (optional)
      }
    ],
    "tenantIds": ["string"]
  }
}
```

### User Not Found Response

```json theme={null}
{
  "status": "UNKNOWN_USER_ID_ERROR"
}
```

## Response Fields

* **status** (string): "OK" for success, "UNKNOWN\_USER\_ID\_ERROR" if user not found
* **user** (object): User information
  * **id** (string): User's unique identifier
  * **timeJoined** (number): Unix timestamp when user was created
  * **isPrimaryUser** (boolean): Whether this is a primary user (for account linking)
  * **emails** (array): All email addresses associated with this user
  * **phoneNumbers** (array): All phone numbers associated with this user
  * **thirdParty** (array): Third-party provider information
  * **loginMethods** (array): All authentication methods available for this user
    * **recipeId** (string): Authentication recipe ("emailpassword", "passwordless", "thirdparty")
    * **recipeUserId** (string): User ID specific to this login method
    * **timeJoined** (number): When this login method was added
    * **verified** (boolean): Whether this login method is verified
    * **email** (string, optional): Email for this login method
    * **phoneNumber** (string, optional): Phone number for this login method
    * **thirdParty** (object, optional): Third-party provider details
  * **tenantIds** (array): List of tenant IDs this user belongs to

## Example Usage

### Get User by SuperTokens ID

```bash theme={null}
curl -X GET "https://your-api-domain.com/user/id?userId=fa3b62b4-b06e-44bf-9f6e-e2b45d6c4c1a"
```

### Get User by External ID

If you have user ID mapping configured:

```bash theme={null}
curl -X GET "https://your-api-domain.com/user/id?userId=external-user-123"
```

### Response Example

```json theme={null}
{
  "status": "OK",
  "user": {
    "id": "fa3b62b4-b06e-44bf-9f6e-e2b45d6c4c1a",
    "timeJoined": 1699564800000,
    "isPrimaryUser": true,
    "emails": ["user@example.com"],
    "phoneNumbers": [],
    "thirdParty": [],
    "loginMethods": [
      {
        "recipeId": "emailpassword",
        "recipeUserId": "fa3b62b4-b06e-44bf-9f6e-e2b45d6c4c1a",
        "timeJoined": 1699564800000,
        "verified": true,
        "email": "user@example.com"
      },
      {
        "recipeId": "thirdparty",
        "recipeUserId": "a8c73e91-7b2f-4d9e-8f1a-3c5e7d9b1f2e",
        "timeJoined": 1699651200000,
        "verified": true,
        "email": "user@example.com",
        "thirdParty": {
          "id": "google",
          "userId": "102934812345678901234"
        }
      }
    ],
    "tenantIds": ["public"]
  }
}
```

## Implementation Details

* Located in: `src/main/java/io/supertokens/webserver/api/core/GetUserByIdAPI.java:40`
* This is an app-specific API
* The API enforces public tenant access for app-specific queries
* Supports user ID mapping: you can query using either SuperTokens user ID or external user ID
* If a user ID mapping exists, the response contains the external user ID
* User information includes all linked login methods (for account linking feature)

## User ID Mapping

If you've configured user ID mapping (to use your own user IDs), this endpoint:

1. Accepts both SuperTokens IDs and external IDs as input
2. Automatically resolves the mapping
3. Returns the external ID in the response when a mapping exists

## Account Linking

This endpoint returns all login methods for a user when account linking is enabled:

* **isPrimaryUser**: `true` if this is the primary user in an account link
* **loginMethods**: Array of all linked authentication methods
* Each login method has its own `recipeUserId`
* Primary user ID is returned as the main user `id`

## Use Cases

* **User Profile Page**: Fetch complete user information for display
* **Admin Dashboard**: Look up users by ID for support
* **Account Management**: Retrieve user data before updates
* **Multi-factor Authentication**: Check available authentication methods
* **Tenant Verification**: Check which tenants a user belongs to

## Error Handling

### Unknown User ID

If the user ID doesn't exist:

```json theme={null}
{
  "status": "UNKNOWN_USER_ID_ERROR"
}
```

### Invalid Request

If the userId parameter is missing, a 400 Bad Request error is returned.

## Related Endpoints

* [List Users](/api/users/list) - Get a paginated list of users
* [Delete User](/api/users/delete) - Delete a user by ID