How to create a Dash Callback without an output?

Question

It is required for an output to have a callback in Dash, but what if you want to trigger events in the backend without having anything output on the frontend?

Answer 1

Create an empty dummy html.div and set the Output to this div

@callback(
    Output('dummy_div', 'children', allow_duplicate = True),
    ...
)...

Answer 2

Callbacks without output have long been requested from the community and are available from dash version 2.17.0 (2024-05-03) see changelog with fixes in version 2.17.1.