> ## Documentation Index > Fetch the complete documentation index at: https://docs.clearline.me/llms.txt > Use this file to discover all available pages before exploring further. # Get Access Token > Exchange authorization code for access token, or obtain access token using client credentials. **Supported Grant Types:** - `authorization_code`: Exchange authorization code from login flow (requires Basic Auth with client_id:client_secret) - `client_credentials`: Server-to-server authentication for POS systems (requires Basic Auth) - `refresh_token`: Refresh an expired access token **Authentication:** All token requests require HTTP Basic Authentication with base64-encoded `client_id:client_secret` in the Authorization header. ## OpenAPI ````yaml /authentication.openapi.yaml post /connect/token openapi: 3.0.1 info: title: ClearLine Authentication API description: >- OAuth2 authentication endpoints for ClearLine Marketing Platform. Supports both Client Credentials flow (for POS server-to-server) and Authorization Code flow with PKCE (for user authentication). version: v1 servers: - url: https://logintest.clearline.me description: Test Environment - Identity Server - url: https://logindemo.clearline.me description: Demo Environment - Identity Server - url: https://login.clearline.me description: Production Environment - Identity Server security: [] paths: /connect/token: post: tags: - Authentication summary: Get Access Token description: > Exchange authorization code for access token, or obtain access token using client credentials. **Supported Grant Types:** - `authorization_code`: Exchange authorization code from login flow (requires Basic Auth with client_id:client_secret) - `client_credentials`: Server-to-server authentication for POS systems (requires Basic Auth) - `refresh_token`: Refresh an expired access token **Authentication:** All token requests require HTTP Basic Authentication with base64-encoded `client_id:client_secret` in the Authorization header. operationId: OAuth2_Token parameters: - name: Authorization in: header required: true description: >- Basic authentication header: "Basic {Base64(client_id:client_secret)}" schema: type: string example: Basic Y2xvdmVyLWNtYy1tb2JpbGU6Y2xpZW50U2VjcmV0IQ== requestBody: required: true content: application/x-www-form-urlencoded: schema: oneOf: - $ref: '#/components/schemas/AuthorizationCodeTokenRequest' - $ref: '#/components/schemas/ClientCredentialsTokenRequest' - $ref: '#/components/schemas/RefreshTokenRequest' examples: authorizationCode: summary: Authorization Code Exchange (Mobile/PKCE) value: grant_type: authorization_code code: authorization_code_from_callback redirect_uri: clover://auth-callback code_verifier: original_code_verifier_string clientCredentials: summary: Client Credentials (POS Integration) value: grant_type: client_credentials scope: pos_integration refreshToken: summary: Refresh Token value: grant_type: refresh_token refresh_token: your_refresh_token responses: '200': description: Successful token response content: application/json: schema: $ref: '#/components/schemas/TokenResponse' examples: authCodeSuccess: summary: Authorization Code Success value: access_token: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9... token_type: Bearer expires_in: 3600 refresh_token: df8a2f3e... scope: clearline_api clientCredsSuccess: summary: Client Credentials Success value: access_token: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9... token_type: Bearer expires_in: 3600 scope: pos_integration '400': description: Bad request - invalid grant or parameters content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '401': description: Unauthorized - invalid client credentials in Basic Auth header content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' components: schemas: AuthorizationCodeTokenRequest: type: object required: - grant_type - code - redirect_uri - code_verifier properties: grant_type: type: string enum: - authorization_code description: Must be "authorization_code" code: type: string description: The authorization code received from the callback redirect_uri: type: string description: The same redirect_uri used in the authorization request example: clover://auth-callback code_verifier: type: string description: >- The original code_verifier string used to generate code_challenge (43-128 characters) description: >- Token request for Authorization Code flow with PKCE. Requires Basic Auth header with client_id:client_secret. ClientCredentialsTokenRequest: type: object required: - grant_type properties: grant_type: type: string enum: - client_credentials description: Must be "client_credentials" scope: type: string description: Requested scopes - typically "pos_integration" for POS systems example: pos_integration description: >- Token request for Client Credentials flow (POS server-to-server). Requires Basic Auth header with client_id:client_secret. RefreshTokenRequest: type: object required: - grant_type - refresh_token properties: grant_type: type: string enum: - refresh_token description: Must be "refresh_token" refresh_token: type: string description: The refresh token from previous token response description: >- Token request to refresh an expired access token. Requires Basic Auth header with client_id:client_secret. TokenResponse: type: object properties: access_token: type: string description: >- The JWT access token to use in API requests via "Authorization Bearer {token}" header example: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9... token_type: type: string description: Token type - always "Bearer" example: Bearer expires_in: type: integer description: Token lifetime in seconds (typically 3600 = 1 hour) example: 3600 refresh_token: type: string description: >- Refresh token to obtain new access token when current expires (not provided for client_credentials grant) nullable: true example: df8a2f3e... scope: type: string description: The scopes granted by this token example: clearline_api ErrorResponse: type: object properties: error: type: string description: Error code (e.g., invalid_grant, invalid_client, invalid_request) example: invalid_grant error_description: type: string description: Human-readable error description example: The authorization code is invalid or expired ````