default value

[OussamaMerhi]

Is there any way to change the default value for a numeric field from null to zero within an existing hosted feature service?

[IsmaelChivite]

Yes. In Survey123 Connect: use the default XLSForm column. In Survey123 web designer: Select your question in the preview and set the default property in the right panel. In ArcGIS.com: You can set the default value when you create the field but not later).