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**✨ Performant, customizable web apps in pure Python. Deploy in seconds. ✨**

[!NOTE] 🚀 Try Reflex Build – our AI-powered app builder that generates full-stack Reflex applications in seconds.

Introduction

Reflex is a library to build full-stack web apps in pure Python.

Key features:

• Pure Python - Write your app's frontend and backend all in Python, no need to learn Javascript.
• Full Flexibility - Reflex is easy to get started with, but can also scale to complex apps.
• Deploy Instantly - After building, deploy your app with a single command or host it on your own server.

See our architecture page to learn how Reflex works under the hood.

⚙️ Installation

Important: We strongly recommend using a virtual environment to ensure the reflex command is available in your PATH.

🥳 Create your first app

1. Create the project directory

Replace my_app_name with your project name:

mkdir my_app_name
cd my_app_name

2. Install uv

Reflex recommends uv for managing your project environment and dependencies. See the uv installation docs for your platform.

# macOS/Linux
curl -LsSf https://astral.sh/uv/install.sh | sh

# Windows (PowerShell)
powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

3. Initialize the Python project

uv init

4. Add Reflex

Reflex requires Python 3.10+:

uv add reflex

5. Initialize the project

This command initializes a template app in your new directory:

uv run reflex init

6. Run the app

You can run this app in development mode:

uv run reflex run

You should see your app running at http://localhost:3000.

Now you can modify the source code in my_app_name/my_app_name.py. Reflex has fast refreshes so you can see your changes instantly when you save your code.

Troubleshooting

If the reflex command is not on your PATH, run it through uv instead: uv run reflex init and uv run reflex run

🫧 Example App

Let's go over an example: creating an image generation UI around DALL·E. For simplicity, we just call the OpenAI API, but you could replace this with an ML model run locally.

Here is the complete code to create this. This is all done in one Python file!

import reflex as rx
import openai

openai_client = openai.OpenAI()


class State(rx.State):
    """The app state."""

    prompt = ""
    image_url = ""
    processing = False
    complete = False

    def get_image(self):
        """Get the image from the prompt."""
        if self.prompt == "":
            return rx.window_alert("Prompt Empty")

        self.processing, self.complete = True, False
        yield
        response = openai_client.images.generate(
            prompt=self.prompt, n=1, size="1024x1024"
        )
        self.image_url = response.data[0].url
        self.processing, self.complete = False, True


def index():
    return rx.center(
        rx.vstack(
            rx.heading("DALL-E", font_size="1.5em"),
            rx.input(
                placeholder="Enter a prompt..",
                on_blur=State.set_prompt,
                width="25em",
            ),
            rx.button(
                "Generate Image",
                on_click=State.get_image,
                width="25em",
                loading=State.processing,
            ),
            rx.cond(
                State.complete,
                rx.image(src=State.image_url, width="20em"),
            ),
            align="center",
        ),
        width="100%",
        height="100vh",
    )


# Add state and page to the app.
app = rx.App()
app.add_page(index, title="Reflex:DALL-E")

Let's break this down.

**Reflex UI**

Let's start with the UI.

def index():
    return rx.center(...)

This index function defines the frontend of the app.

We use different components such as center, vstack, input, and button to build the frontend. Components can be nested within each other to create complex layouts. And you can use keyword args to style them with the full power of CSS.

Reflex comes with 60+ built-in components to help you get started. We are actively adding more components, and it's easy to create your own components.

**State**

Reflex represents your UI as a function of your state.

class State(rx.State):
    """The app state."""

    prompt = ""
    image_url = ""
    processing = False
    complete = False

The state defines all the variables (called vars) in an app that can change and the functions that change them.

Here the state is comprised of a prompt and image_url. There are also the booleans processing and complete to indicate when to disable the button (during image generation) and when to show the resulting image.

**Event Handlers**

def get_image(self):
    """Get the image from the prompt."""
    if self.prompt == "":
        return rx.window_alert("Prompt Empty")

    self.processing, self.complete = True, False
    yield
    response = openai_client.images.generate(prompt=self.prompt, n=1, size="1024x1024")
    self.image_url = response.data[0].url
    self.processing, self.complete = False, True

Within the state, we define functions called event handlers that change the state vars. Event handlers are the way that we can modify the state in Reflex. They can be called in response to user actions, such as clicking a button or typing in a text box. These actions are called events.

Our DALL·E app has an event handler, get_image which gets this image from the OpenAI API. Using yield in the middle of an event handler will cause the UI to update. Otherwise the UI will update at the end of the event handler.

**Routing**

Finally, we define our app.

app = rx.App()

We add a page from the root of the app to the index component. We also add a title that will show up in the page preview/browser tab.

app.add_page(index, title="DALL-E")

You can create a multi-page app by adding more pages.

📑 Resources

✅ Status

Reflex launched in December 2022 with the name Pynecone.

🚀 Introducing Reflex Build — Our AI-Powered Builder Reflex Build uses AI to generate complete full-stack Python applications. It helps you quickly create, customize, and refine your Reflex apps — from frontend components to backend logic — so you can focus on your ideas instead of boilerplate code. Whether you’re prototyping or scaling, Reflex Build accelerates development by intelligently scaffolding and optimizing your app’s entire stack.

Alongside this, Reflex Cloud launched in 2025 to offer the best hosting experience for your Reflex apps. We’re continuously improving the platform with new features and capabilities.

Reflex has new releases and features coming every week! Make sure to :star: star and :eyes: watch this repository to stay up to date.

Contributing

We welcome contributions of any size! Below are some good ways to get started in the Reflex community.

• Join Our Discord: Our Discord is the best place to get help on your Reflex project and to discuss how you can contribute.
• GitHub Discussions: A great way to talk about features you want added or things that are confusing/need clarification.
• GitHub Issues: Issues are an excellent way to report bugs. Additionally, you can try and solve an existing issue and submit a PR.

We are actively looking for contributors, no matter your skill level or experience. To contribute check out CONTRIBUTING.md

All Thanks To Our Contributors:

License

Reflex is open-source and licensed under the Apache License 2.0.