# Authentication methods All requests to the CARTO APIs (and therefore all developments using CARTO) must be authenticated. When starting a project or building an application, we recommend choosing one between these three strategies: * **Authentication via API Access Tokens:** These types of permanent tokens are simple, easy to generate, restrictive, and not tied to specific users. You can use them directly to authenticate your requests. [Read more about API Access Tokens](/carto-for-developers/key-concepts/authentication-methods/api-access-tokens.md). * **Authentication via Single Page OAuth Client:** Authenticate each user separately by presenting them a login where they need to introduce their CARTO credentials — or their SSO credentials if configured. Once set up, your app will obtain and use [*OAuth Access Tokens*](/carto-for-developers/key-concepts/authentication-methods/oauth-access-tokens.md) for each user independently. [Read more about Single Page Applications](/carto-for-developers/key-concepts/authentication-methods/applications.md#single-page-application-spa). * **Authentication via Machine-to-Machine OAuth Client:** Obtain an [*OAuth Access Token*](/carto-for-developers/key-concepts/authentication-methods/oauth-access-tokens.md) on demand (using a backend application) without the user having to log in and use it to authenticate all your requests. [Read more about Machine-to-Machine Applications](/carto-for-developers/key-concepts/authentication-methods/applications.md#machine-to-machine-authentication-m2m). --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.carto.com/carto-for-developers/key-concepts/authentication-methods.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.