> For the complete documentation index, see [llms.txt](https://docs.tryterra.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tryterra.co/unified-api/user-authentication.md).

# User authentication

User authentication allows Terra to accessing your users' health and fitness data and is essential to using the Unified API.

Authentication allows your end-users to grant your application permission to retrieve data from their wearables or fitness platforms (like Fitbit, Garmin, Oura, etc.). Once a user is successfully authenticated, Terra automatically pushes their health data events to your configured destination.

***

## Implementation guides

{% stepper %}
{% step %}
[**Authentication flow overview**](/unified-api/user-authentication/authentication-flow.md)

Get an overview of the user authentication process, from the initial user action in your app to receiving their Terra User ID.
{% endstep %}

{% step %}
[**Authenticating with the Terra widget**](/unified-api/user-authentication/implementation-terra-widget.md)

The quickest way to get started. Learn how to integrate Terra's pre-built, customisable UI to handle the provider selection and authentication process with a single API call.
{% endstep %}

{% step %}
[**Handling authentication events**](/unified-api/user-authentication/handling-authentication-events.md)

Understand the different types of authentication events Terra sends (success, failure, deauthorisation) and how to process their payloads effectively.
{% endstep %}
{% endstepper %}

***

## Configuration

[**Customising authentication redirects**](/unified-api/user-authentication/customising-authentication-redirects.md)

* Learn how to customise the <mark style="color:green;">success</mark> or <mark style="color:red;">failure</mark> screen that users see after they complete the authentication flow but before they are redirected back to your app.

[**Authenticating with your own UI**](/unified-api/user-authentication/implementation-custom-ui.md)

* For maximum control over the user experience. This guide details how to build your own device connection screen and use Terra's API to authenticate users with specific providers.

{% hint style="info" %}
💡 **Pro-Tip:** Start with the widget because it’s the:

1. **Fastest way to go live:** no need to build or maintain your own auth UI
2. **Easiest to implement:** just one backend call to generate the link
3. **Optimized UX:** designed and tested for high end-user completion rates across devices and platforms
   {% endhint %}

***

## ✅ Checklist

{% hint style="success" %}

### Implementing the User Authentication in your App

1. **API**:
   1. **Credentials:** Did you find your Terra API Keys and Dev-ID in your Terra Dashboard?
   2. **Endpoint**: Did you make a **successful** **request** from your backend to one of the /auth endpoints?
      1. <mark style="color:orange;">`POST`</mark> `/auth/generateWidgetSession`
      2. <mark style="color:orange;">`POST`</mark> `/auth/authenticateUser?resource=oura`
   3. **Response**: Did you get a **200 response** and parse the authentication url? Either:
      1. `"url"`: the widget screen (via the widget endpoint)
      2. `"auth_url"` : the provider's login screen (via the authenticateUser endpoint)
   4. **End-user:** Was your end-user redirected to an **Auth** **Success** **Screen**?
2. **Event**: Did you receive an **Success "Authentication Event"** to your destination?
3. **Database**: Did you save this user in your Database using `user_id` ?
   {% endhint %}