mounted events require the `mounted` feature on dioxus-web

Error message

mounted events require the `mounted` feature on dioxus-web

What it means

A mounted event handler was registered on wasm but the dioxus-web crate was built without its `mounted` feature, so MountedData cannot be constructed. The cfg-gated conversion arm is absent and the fallback error fires when a mounted event arrives.

Source

Thrown at packages/web/src/events/mod.rs:150

                ))
            };
            convert_keyboard_data(KeyboardData) => web_sys::KeyboardEvent;
            convert_media_data(MediaData) => web_sys::Event;
            convert_mounted_data(MountedData) => web_sys::Element => |event| {
                #[cfg(feature = "mounted")]
                {
                    Synthetic::new(
                        event
                            .downcast::<web_sys::Element>()
                            .expect("event should be a web_sys::Element")
                            .clone(),
                    )
                    .into()
                }
                #[cfg(not(feature = "mounted"))]
                {
                    let _ = event;
                    panic!("mounted events require the `mounted` feature on dioxus-web")
                }
            };
            convert_mouse_data(MouseData) => web_sys::MouseEvent;
            convert_pointer_data(PointerData) => web_sys::PointerEvent;
            convert_resize_data(ResizeData) => web_sys::CustomEvent => |event| {
                Synthetic::<web_sys::ResizeObserverEntry>::from(downcast_event(event).raw.clone()).into()
            };
            convert_scroll_data(ScrollData) => web_sys::Event;
            convert_selection_data(SelectionData) => web_sys::Event;
            convert_toggle_data(ToggleData) => web_sys::Event;
            convert_touch_data(TouchData) => web_sys::TouchEvent;
            convert_transition_data(TransitionData) => web_sys::TransitionEvent;
            convert_visible_data(VisibleData) => web_sys::CustomEvent => |event| {
                Synthetic::<web_sys::IntersectionObserverEntry>::from(downcast_event(event).raw.clone()).into()
            };
            convert_wheel_data(WheelData) => web_sys::WheelEvent;
        }
    };

View on GitHub (pinned to 24f6a829df)

Solutions

Enable the mounted feature on dioxus-web to use mounted events.

Defensive patterns

Strategy: validation

When it happens

Trigger: Thrown at packages/web/src/events/mod.rs:150 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of DioxusLabs/dioxus@24f6a829df (2026-08-23). Data as JSON: /api/errors/41a3bec7898e8bd3. Report an issue: GitHub.