zitadel/apps/docs/content/sdk-examples/flask.mdx

---
title: Flask
description: "Integrate ZITADEL authentication into Flask applications using the OAuth 2.0 PKCE flow."
sidebar_label: Flask
framework_url: https://flask.palletsprojects.com
auth_library: "Authlib"
auth_library_url: https://authlib.org
example_repo: https://github.com/zitadel/example-auth-flask
auth_flow: pkce
status: stable
---

## Overview

[Flask](https://flask.palletsprojects.com) is a lightweight WSGI web application framework for Python. It's designed to make getting started quick and easy, with the ability to scale up to complex applications. This example demonstrates how to integrate **Zitadel** using the **[OAuth 2.0 PKCE flow](https://oauth.net/2/pkce/)** to authenticate users securely and maintain sessions across your application.

#### Auth library

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

---

## What this example demonstrates

This example shows a complete authentication implementation using [Flask](https://flask.palletsprojects.com) with [Zitadel](https://zitadel.com/docs). 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](https://zitadel.com/docs/apis/openidoauth/claims) after successful authentication.

The application implements server-side session management with Flask's built-in session handling, storing authentication state securely in encrypted cookies. Protected routes use the `@require_auth` decorator 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](https://zitadel.com/docs/apis/openidoauth/claims) and [session metadata](https://zitadel.com/docs/apis/openidoauth/endpoints#token_endpoint).

The application demonstrates proper **[federated logout](https://zitadel.com/docs/guides/integrate/login/oidc/logout)** by terminating sessions both locally and with Zitadel's [end-session endpoint](https://zitadel.com/docs/guides/integrate/login/oidc/logout), complete with CSRF protection using state parameters. Additionally, it includes automatic [token refresh](https://zitadel.com/docs/apis/openidoauth/endpoints) using [refresh tokens](https://zitadel.com/docs/apis/openidoauth/grant-types#refresh-token) to maintain long-lived sessions without requiring users to re-authenticate. The example uses [Zitadel-specific scopes](https://zitadel.com/docs/apis/openidoauth/scopes) 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)](https://zitadel.com/docs/guides/manage/console/roles).

---

## Getting started

### Prerequisites

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

1. Create a new Web application in your [Zitadel project](https://zitadel.com/docs/guides/manage/console/projects-overview)
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](https://zitadel.com/docs/apis/openidoauth/grant-types#refresh-token) in Token Settings for long-lived sessions

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

### Run the example

Once you have your [Zitadel application](https://zitadel.com/docs/guides/manage/console/applications-overview) configured:

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

---

## Learn more and resources

* [PKCE concept](https://oauth.net/2/pkce/)
* [Federated logout](https://zitadel.com/docs/guides/integrate/login/oidc/logout)
* [OIDC integration guide](https://zitadel.com/docs/guides/integrate/login/oidc/login-users)
* [Flask documentation](https://flask.palletsprojects.com)
* [Authlib documentation](https://authlib.org)
* [Example repository](https://github.com/zitadel/example-auth-flask)