Hi @baobob, the “x unified” hovermode does not work (yet) across subplots. We have an open issue for this which you can subscribe to https://github.com/plotly/plotly.js/issues/4755. If you’re only interested in the spike line extended to the other subplots you can do this with
fig.update_traces(xaxis='x1')
(imposing that there is only one xaxis)
but this will just give you the extended spike line, not the hover information of all subplots.