How to replace default map?

[Terramoto]

Hello,

How i can replace mapbox with openstreetmap as the default map?

[vcoppe]

As a user, you can simply switch between map layers and the last one used will be remembered and used by default when you come back to the website.
If your question is related to your own deployment, you can check in js/button.js where the addTo method is used to add the default map layer to the map and do it for the OSM layer instead.