Class App

reflex/app.py:312–1531

The main Reflex app that encapsulates the backend and frontend. Every Reflex app needs an app defined in its main module. ```python # app.py import reflex as rx # Define state and pages ... app = rx.App( # Set global level style. style={...}, #

@dataclasses.dataclass()
class App(MiddlewareMixin, LifespanMixin):
    """The main Reflex app that encapsulates the backend and frontend.

    Every Reflex app needs an app defined in its main module.

    ```python
    # app.py
    import reflex as rx

    # Define state and pages
    ...

    app = rx.App(
        # Set global level style.
        style={...},
        # Deprecated legacy shortcut for the Radix Themes plugin.
        theme=rx.theme(accent_color="blue"),
    )
    ```

    Attributes:
        theme: Deprecated legacy shortcut for configuring the app-level Radix [theme](https://reflex.dev/docs/styling/theming/).
        style: The [global style](https://reflex.dev/docs/styling/overview/#global-styles) for the app.
        stylesheets: A list of URLs to [stylesheets](https://reflex.dev/docs/styling/custom-stylesheets/) to include in the app.
        reset_style: Whether to include CSS reset for margin and padding. Defaults to True.
        app_wraps: App wraps to be applied to the whole app. Expected to be a dictionary of (order, name) to a function that takes whether the state is enabled and optionally returns a component.
        extra_app_wraps: Extra app wraps to be applied to the whole app.
        head_components: Components to add to the head of every page.
        sio: The Socket.IO AsyncServer instance.
        html_lang: The language to add to the html root tag of every page.
        html_custom_attrs: Attributes to add to the html root tag of every page.
        enable_state: Whether to enable [state](https://reflex.dev/docs/state/overview/) for the app. If False, the app will not use state.
        admin_dash: Admin dashboard to view and manage the database.
        frontend_exception_handler: Frontend [error handler](https://reflex.dev/docs/utility-methods/exception-handlers/) function.
        backend_exception_handler: Backend [error handler](https://reflex.dev/docs/utility-methods/exception-handlers/) function.
        toaster: Put the [toast](https://reflex.dev/docs/library/overlay/toast/) provider in the app wrap.
        api_transformer: One or more transforms applied to the backend ASGI app before it runs — mount a FastAPI/Starlette app or wrap it in ASGI middleware. See the [API Transformer docs](https://reflex.dev/docs/api-routes/overview/) for examples.
    """

    theme: Component | None = dataclasses.field(default=None)

    style: ComponentStyle = dataclasses.field(default_factory=dict)

    stylesheets: list[str] = dataclasses.field(default_factory=list)

    reset_style: bool = dataclasses.field(default=True)

    app_wraps: dict[tuple[int, str], Callable[[bool], Component | None]] = (
        dataclasses.field(
            default_factory=lambda: {
                (55, "ErrorBoundary"): (
                    lambda stateful: default_error_boundary(
                        **({"on_error": noop()} if not stateful else {})
                    )
                ),
                (5, "Overlay"): (
                    lambda stateful: default_overlay_component() if stateful else None
                ),