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

# Get passkey assertion options for sign-in

> First half of the passkey second factor. Exchanges the pre-auth token for WebAuthn authentication options (from @simplewebauthn/server) covering every passkey on the account, and stores the challenge server-side for /v1/auth/2fa/verify. Pass `data` straight to `startAuthentication()`. Not rate-limited.



## OpenAPI

````yaml /api-reference/openapi.yaml post /v1/auth/2fa/options
openapi: 3.1.0
info:
  title: Server.Express API
  version: 1.0.0
  description: >-
    The customer-facing Server.Express API: auth, billing, tickets, cloud and
    dedicated servers, hosting, reselling and account management. Every response
    uses the `{ success, data | error }` envelope.
  contact:
    name: Server.Express
    url: https://server.express
servers:
  - url: https://my.server.express/api
    description: Production
security:
  - bearerAuth: []
  - apiToken: []
tags:
  - name: API Tokens
  - name: Account
  - name: Auth
  - name: Cloud
  - name: Coupons
  - name: Credits
  - name: Dashboard
  - name: Dedicated
  - name: Health
  - name: Hosting
  - name: Integrations
  - name: Invoices
  - name: Livechat
  - name: Notifications
  - name: Passkeys
  - name: Payments
  - name: Products
  - name: Public
  - name: Public Invoices
  - name: Public Tools
  - name: Reseller
  - name: SSH Keys
  - name: Services
  - name: Tasks
  - name: Teams
  - name: Tickets
  - name: Web Hosting
  - name: Webhooks
paths:
  /v1/auth/2fa/options:
    post:
      tags:
        - Auth
      summary: Get passkey assertion options for sign-in
      description: >-
        First half of the passkey second factor. Exchanges the pre-auth token
        for WebAuthn authentication options (from @simplewebauthn/server)
        covering every passkey on the account, and stores the challenge
        server-side for /v1/auth/2fa/verify. Pass `data` straight to
        `startAuthentication()`. Not rate-limited.
      operationId: publicAuthTwoFactorPasskeyOptions
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - preAuthToken
              properties:
                preAuthToken:
                  type: string
      responses:
        '200':
          description: WebAuthn request options.
          content:
            application/json:
              schema:
                type: object
                required:
                  - success
                  - data
                properties:
                  success:
                    type: boolean
                    const: true
                  data:
                    $ref: '#/components/schemas/PublicAuthPasskeyRequestOptions'
        '400':
          $ref: '#/components/responses/BadRequest'
        '500':
          $ref: '#/components/responses/ServerError'
      security: []
components:
  schemas:
    PublicAuthPasskeyRequestOptions:
      type: object
      description: >-
        WebAuthn PublicKeyCredentialRequestOptionsJSON, as produced by
        @simplewebauthn/server.
      required:
        - challenge
      properties:
        challenge:
          type: string
          description: Base64url challenge. Single use.
        timeout:
          type: integer
        rpId:
          type: string
        allowCredentials:
          type: array
          items:
            type: object
            required:
              - id
              - type
            properties:
              id:
                type: string
                description: Base64url credential id.
              type:
                type: string
                const: public-key
              transports:
                type: array
                items:
                  type: string
        userVerification:
          type: string
          const: preferred
        extensions:
          type: object
      additionalProperties: true
    ErrorResponse:
      type: object
      required:
        - success
        - error
      properties:
        success:
          type: boolean
          const: false
        error:
          type: string
          description: Human-readable error message.
      additionalProperties: true
  responses:
    BadRequest:
      description: Validation failed or the request is malformed.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorResponse'
    ServerError:
      description: Unexpected server error.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorResponse'
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT
      description: >-
        Session access token (JWT) from POST /v1/auth/login or /v1/auth/refresh.
        A session satisfies every API scope.
    apiToken:
      type: http
      scheme: bearer
      bearerFormat: se_live_<prefix>_<secret>
      description: >-
        Personal API token created under Settings → API tokens. Only routes
        guarded by verifyApiAuth accept it, and the token must carry the scope
        named in the operation's x-required-scope.

````

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