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

# Choosing an Authentication Method

> Decide whether your integration should use a bearer token or OAuth

Choose your authentication method based on who owns the thanks.io account and where the integration runs.

## Use a Bearer Token If

* You are building an internal integration for a single thanks.io account.
* Your server will send API requests on behalf of your own business.
* You want the fastest path to testing and production.

This is the simplest option and the right default for most direct API integrations.

## Use OAuth If

* You are building a SaaS or partner integration that connects multiple customer accounts.
* Your users need to authorize your application to access their own thanks.io account.
* You need to store per-customer access and refresh tokens.

OAuth is the right choice when your application connects many thanks.io accounts and each user must explicitly grant access.

## Quick Decision Guide

| If your integration needs to...                              | Use                                          |
| ------------------------------------------------------------ | -------------------------------------------- |
| Send mail from one thanks.io account you control             | [Bearer Token](/authentication/bearer-token) |
| Let each customer connect their own thanks.io account        | [OAuth](/authentication/oauth)               |
| Get a first request working quickly                          | [Bearer Token](/authentication/bearer-token) |
| Support account connection, authorization, and token refresh | [OAuth](/authentication/oauth)               |

## Next Steps

* For the fastest first request, continue to [Bearer Token](/authentication/bearer-token) and [Quickstart](/quickstart).
* For multi-account integrations, continue to [OAuth](/authentication/oauth).