Is it possible to publish a joined layer to ArcGIS Online?

Answer

No, it is not possible to publish a joined layer to ArcGIS Online as it is not a permanent layer. The joined layer is saved with the feature layer in the map document or map file but it is not saved in the data source of the layer.

When attempting to publish the joined layer from ArcMap to ArcGIS Online, fields created from the joined layer are not displayed in the attribute table of its hosted feature layer. In ArcGIS Pro, attempting to publish a joined layer to ArcGIS Online returns an error message, '00226: In-memory joins and relates are not supported.'

However, the joined layer can be exported as a database feature class in ArcGIS Pro or ArcMap, and published to ArcGIS Online. The following are steps to export the joined layer and publish it to ArcGIS Online.

In ArcGIS Pro

1. Launch ArcGIS Pro and log in to ArcGIS Online with privileges to create content and publish hosted feature layers.
2. Open the project containing the joined layer.
3. In the Contents pane, browse to and export the joined layer as a database feature class. Refer to ArcGIS Pro: Export feature classes for more information. The new feature class created is automatically added to the map.
4. Publish the layer as a hosted feature layer to ArcGIS Online. Refer to ArcGIS Pro: Share a web feature layer using the default configuration for steps to do this.

In ArcMap

1. Launch ArcMap and log in to ArcGIS Online.
2. Open the project containing the joined layer.
3. In the Table Of Contents pane, browse to and export the joined layer as a database feature class. Refer to ArcMap: Exporting features for more information.
4. When prompted, click Yes.

5. Publish the layer as a hosted feature layer to ArcGIS Online. Refer to ArcMap: Publish hosted web layers for steps to do this.

Alternatively, use the Join Features tool in ArcGIS Online Map Viewer to create a new joined layer between the feature layers. Refer to FAQ: Does ArcGIS Online support joins and relates? for more information.