# FastAPI

## [Overview](/content/docs/sdk-examples/fastapi#overview/index.html)

[FastAPI](https://fastapi.tiangolo.com/) is a modern, fast (high-performance) web framework for building APIs with Python based on standard Python type hints. This example demonstrates how to integrate **[Zitadel](/content/docs/index.html)** using the **[OAuth 2.0 PKCE flow](https://oauth.net/2/pkce/)** to authenticate users securely and maintain sessions across your application.

#### [Auth library](/content/docs/sdk-examples/fastapi#auth-library/index.html)

This example uses **[Authlib](https://authlib.org/)**, the standard authentication library for Python web frameworks. Authlib implements the [OpenID Connect (OIDC)](/content/docs/apis/openidoauth/endpoints/index.html) flow, manages [PKCE](https://oauth.net/2/pkce/), performs secure token exchange, and provides session management helpers. The integration uses Authlib's Starlette client which seamlessly handles OAuth 2.0 flows within FastAPI applications built on [Starlette](https://www.starlette.io/).

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## [What this example demonstrates](/content/docs/sdk-examples/fastapi#what-this-example-demonstrates/index.html)

This example shows a complete authentication implementation using [FastAPI](https://fastapi.tiangolo.com/) with [Zitadel](/content/docs/index.html). Users start on a public landing page, click a login button to authenticate with Zitadel using the secure [PKCE flow](https://oauth.net/2/pkce/), and are redirected to a protected profile page displaying their [user information](/content/docs/apis/openidoauth/claims/index.html) after successful authentication.

The application implements server-side session management with Starlette's session middleware, storing authentication state securely in encrypted cookies. Protected routes use the `require_auth` dependency to automatically redirect unauthenticated users to the sign-in flow, ensuring only authenticated users can access sensitive areas. The profile page displays comprehensive user information including [OIDC claims](/content/docs/apis/openidoauth/claims/index.html) and [session metadata](/content/docs/apis/openidoauth/endpoints#token_endpoint/index.html).

The application demonstrates proper **[federated logout](/content/docs/guides/integrate/login/oidc/logout/index.html)** by terminating sessions both locally and with Zitadel's [end-session endpoint](/content/docs/guides/integrate/login/oidc/logout/index.html), complete with CSRF protection using state parameters. Additionally, it includes automatic [token refresh](/content/docs/apis/openidoauth/endpoints/index.html) using [refresh tokens](/content/docs/apis/openidoauth/grant-types#refresh-token/index.html) to maintain long-lived sessions without requiring users to re-authenticate. The example uses [Zitadel-specific scopes](/content/docs/apis/openidoauth/scopes/index.html) like `urn:zitadel:iam:user:metadata` and `urn:zitadel:iam:org:projects:roles` to access extended user attributes and role information for implementing [role-based access control (RBAC)](/content/docs/guides/manage/console/roles/index.html).

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## [Getting started](/content/docs/sdk-examples/fastapi#getting-started/index.html)

### [Prerequisites](/content/docs/sdk-examples/fastapi#prerequisites/index.html)

Before running this example, you need to create and configure a PKCE application in the [ZITADEL Management Console](/content/docs/guides/manage/console/console-overview/index.html). Follow the PKCE application setup guide to:

1. Create a new Web application in your [Zitadel project](/content/docs/guides/manage/console/projects-overview/index.html)
2. Configure it to use the PKCE authentication method
3. Set up your redirect URIs (e.g., `http://localhost:3000/auth/callback` for development)
4. Configure post-logout redirect URIs (e.g., `http://localhost:3000/auth/logout/callback`)
5. Copy your **Client ID** for use in the next steps
6. Optionally enable [refresh tokens](/content/docs/apis/openidoauth/grant-types#refresh-token/index.html) in Token Settings for long-lived sessions

> **Note:** Make sure to enable **Dev Mode** in the [ZITADEL Management Console](/content/docs/guides/manage/console/console-overview/index.html) if you're using HTTP URLs during local development. For production, always use HTTPS URLs and disable Dev Mode.

### [Run the example](/content/docs/sdk-examples/fastapi#run-the-example/index.html)

Once you have your [Zitadel application](/content/docs/guides/manage/console/applications-overview/index.html) configured:

1. Clone the [repository](https://github.com/zitadel/example-auth-fastapi).
2. Create a `.env` file (copy from `.env.example`) and configure it with the values from your [Zitadel application](/content/docs/guides/manage/console/applications-overview/index.html). **Use these exact environment variable names:**

```bash
PY_ENV=development
PORT=3000
SESSION_SECRET=your-very-secret-and-strong-session-key
ZITADEL_DOMAIN=https://your-zitadel-domain
ZITADEL_CLIENT_ID=your-zitadel-application-client-id
ZITADEL_CLIENT_SECRET=your-randomly-generated-client-secret
ZITADEL_CALLBACK_URL=http://localhost:3000/auth/callback
ZITADEL_POST_LOGIN_URL=/profile
ZITADEL_POST_LOGOUT_URL=http://localhost:3000/auth/logout/callback
```

Replace these values with:
   - Your actual [Zitadel instance URL](/content/docs/guides/manage/console/default-settings/index.html) for `ZITADEL_DOMAIN` (the issuer)
   - The **Client ID** you copied when creating the application for `ZITADEL_CLIENT_ID`
   - The **redirect URI** you configured in the PKCE setup for `ZITADEL_CALLBACK_URL` (must match exactly)
   - The **post-logout redirect URI** for `ZITADEL_POST_LOGOUT_URL`
   - A strong random string for `SESSION_SECRET` (generate using: `python -c "import secrets; print(secrets.token_hex(32))"`)
   - A randomly generated string for `ZITADEL_CLIENT_SECRET` (generate using: `python -c "import secrets; print(secrets.token_hex(32))"`)
3. Install dependencies using [Poetry](https://python-poetry.org/) with `poetry install` and start the development server with `poetry run python run.py` to verify the authentication flow end-to-end.

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## [Learn more and resources](/content/docs/sdk-examples/fastapi#learn-more-and-resources/index.html)

- [PKCE concept](https://oauth.net/2/pkce/)
- [Federated logout](/content/docs/guides/integrate/login/oidc/logout/index.html)
- [OIDC integration guide](/content/docs/guides/integrate/login/oidc/login-users/index.html)
- [FastAPI documentation](https://fastapi.tiangolo.com/)
- [Authlib documentation](https://authlib.org/)
- [Example repository](https://github.com/zitadel/example-auth-fastapi)