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

> Initialize a login with Webauthn.

# Initialize WebAuthn login

<Warning>
  Deprecated. Please use the [Flow API](/api-reference/flow/registration) instead. [What's the Flow API?](/using-the-api/understanding-the-flow-api).
</Warning>

Returns a JSON representation of CredentialRequestOptions for use
with the Webauthn API's `navigator.credentials.get()`.

Omitting the optional request body or using an empty JSON object results in generation of request options for a
login using a [discoverable credential](https://www.w3.org/TR/webauthn-2/#client-side-discoverable-public-key-credential-source)
(i.e. they will not contain
[allowCredentials](https://www.w3.org/TR/webauthn-2/#dom-publickeycredentialrequestoptions-allowcredentials)).

<Note>
  The Webauthn API uses binary data represented by ArrayBuffers for certain input/output values.
  The Hanko API returns these values as base64url-encoded, so they must be converted to ArrayBuffers
  when passed to the Webauthn API. Similarly, Webauthn API output must be converted to base64url-encoded values
  when passed to the Hanko API (e.g. using the [webauthn-json](https://github.com/github/webauthn-json) library).
</Note>


## OpenAPI

````yaml openapi-public post /webauthn/login/initialize
openapi: 3.0.0
info:
  version: 1.2.0
  title: Hanko Public API
  description: >
    ## Introduction


    This is the OpenAPI specification for the [Hanko Public
    API](https://github.com/teamhanko/hanko/blob/main/backend/README.md#basic-usage).


    ## Authentication


    The API uses [JSON Web Tokens](https://www.rfc-editor.org/rfc/rfc7519.html)
    (JWTs) for authentication.

    JWTs are verified using [JSON Web
    Keys](https://www.rfc-editor.org/rfc/rfc7517) (JWK).

    JWKs can be
    [configured](https://github.com/teamhanko/hanko/blob/main/backend/docs/Config.md#all-available-config-options)

    through the `secrets.keys` options. The API also publishes public
    cryptographic keys as a

    [JWK set](https://www.rfc-editor.org/rfc/rfc7517#section-2) through the
    `.well-known/jwks.json` endpoint

    to enable clients to verify token signatures.

    JWTs must be provided on requests to protected endpoints using one of the
    following schemes:


    ### CookieAuth


    **Security Scheme Type**: `API Key`


    **Cookie parameter name**: `hanko`


    The JWT must be provided in a Cookie with the name `hanko`.


    ### BearerTokenAuth


    **Security Scheme Type**: `http`


    **HTTP Authorization Scheme**: `Bearer`


    **Bearer format**: `JWT`


    The JWT must be provided in an HTTP Authorization header with bearer type:
    `Authorization: Bearer <JWT>`.


    ## Cross-Origin Resource Sharing

    Cross-Origin Resource Sharing (CORS) can be currently

    [configured](https://github.com/teamhanko/hanko/blob/main/backend/docs/Config.md#all-available-config-options)

    for public endpoints via the `server.public.cors` options.


    ---
  contact:
    email: developers@hanko.io
  license:
    name: AGPL-3.0-or-later
    url: https://www.gnu.org/licenses/agpl-3.0.txt
servers:
  - url: https://{tenant_id}.hanko.io
    variables:
      tenant_id:
        default: ''
        description: The (UU)ID of a tenant. Replace the default value with your tenant ID.
security: []
externalDocs:
  description: More about Hanko
  url: https://github.com/teamhanko/hanko
paths:
  /webauthn/login/initialize:
    post:
      tags:
        - WebAuthn
      summary: Initialize WebAuthn login
      description: >
        Initialize a login with Webauthn. Returns a JSON representation of
        CredentialRequestOptions for use

        with the Webauthn API's `navigator.credentials.get()`.


        Omitting the optional request body or using an empty JSON object results
        in generation of request options for a

        login using a [discoverable
        credential](https://www.w3.org/TR/webauthn-2/#client-side-discoverable-public-key-credential-source)

        (i.e. they will not contain

        [allowCredentials](https://www.w3.org/TR/webauthn-2/#dom-publickeycredentialrequestoptions-allowcredentials)).


        *Note*: The Webauthn API uses binary data represented by ArrayBuffers
        for certain input/output values.

        The Hanko API returns these values as base64url-encoded, so they must be
        converted to ArrayBuffers

        when passed to the Webauthn API. Similarly, Webauthn API output must be
        converted to base64url-encoded values

        when passed to the Hanko API (e.g. using the
        [webauthn-json](https://github.com/github/webauthn-json) library).
      operationId: webauthnLoginInit
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                user_id:
                  description: >-
                    The ID of the user on whose behalf WebAuthn login should be
                    performed
                  allOf:
                    - $ref: '#/components/schemas/UUID4'
      responses:
        '200':
          description: Successful initialization
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CredentialRequestOptions'
              examples:
                non-disco:
                  summary: Non-Discoverable credentials
                  value:
                    publicKey:
                      challenge: qgOI+0KpGnl9NOqaT6dfsYvi96R87LgpErnvePeOgSU=
                      timeout: 60000
                      rpId: localhost
                      allowCredentials:
                        - type: public-key
                          id: Mepptysj5ZZrTlg0qiLbsZ068OtQMeGVAikVy2n1hvvG...
                      userVerification: required
                disco:
                  summary: Discoverable credentials
                  value:
                    challenge: qgOI+0KpGnl9NOqaT6dfsYvi96R87LgpErnvePeOgSU=
                    timeout: 60000
                    rpId: localhost
                    userVerification: required
        '400':
          $ref: '#/components/responses/BadRequest'
        '500':
          $ref: '#/components/responses/InternalServerError'
      deprecated: true
components:
  schemas:
    UUID4:
      type: string
      format: uuid4
      example: c339547d-e17d-4ba7-8a1d-b3d5a4d17c1c
    CredentialRequestOptions:
      description: Options for assertion generation with the WebAuthn API
      externalDocs:
        url: https://www.w3.org/TR/webauthn-2/#dictionary-assertion-options
      type: object
      properties:
        publicKey:
          type: object
          properties:
            challenge:
              type: string
              format: base64url
              example: qgOI+0KpGnl9NOqaT6dfsYvi96R87LgpErnvePeOgSU=
            timeout:
              type: integer
              format: int64
              example: 60000
            rpId:
              type: string
              example: localhost
            allowCredentials:
              type: array
              items:
                type: object
                properties:
                  type:
                    type: string
                    enum:
                      - public-key
                    example: public-key
                  id:
                    type: string
                    format: base64url
                    example: Mepptysj5ZZrTlg0qiLbsZ068OtQMeGVAikVy2n1hvvG...
            userVerification:
              type: string
              enum:
                - required
                - preferred
                - discouraged
              example: required
    Error:
      type: object
      required:
        - code
        - message
      properties:
        code:
          type: integer
          format: int32
        message:
          type: string
  responses:
    BadRequest:
      description: Bad Request
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
          example:
            code: 400
            message: Bad Request
    InternalServerError:
      description: Internal server error
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
          example:
            code: 500
            message: Internal Server Error

````