I have a geotiff on my web server where the app is stored which I would like to integrate into a webmap as basemap. Is that possible without publishing the geotiff as a service?
Frieda,
There is the MapImageLayer that allows for adding a geoTiff to the map but I don't think you can set that as the basemap:
MapImageLayer | API Reference | ArcGIS API for JavaScript
So yes you will need to publish a service.