Skip to content

Layer item vs. Layer

When publishing a service, it is possible to include multiple layers into that single service. That service will have a single configuration that applies to all the layers. The service will be referenced in the portal by a layer item. A single layer item might therefore reference multiple individual layers.

Confusingly, people sometimes say “layer” when they mean “layer item”. A layer item is like a container for layers. Layers are also called sublayers to help differentiate them from the layer item they are contained within. You can think of a layer item like a group layer in ArcGIS Pro. In fact, if you add a layer item to ArcGIS Pro, it will come into the map as a group layer.

In the portal, layers do not have their own Item ID, and you do not manage access to them individually. Sharing, tags, and categories apply to the layer item, not the layers within it. You do have control over the representation of individual layers by separately configuring their symbology, filters, and popups.

Even though layers do not have an Item ID in the portal, they do have a unique Layer ID. This Layer ID allows each layer to reference its own unique REST endpoint, with the Layer ID at the end of the general service URL. This unique REST endpoint means that layers can be added individually to a map, separate from other layers in the same layer item. If the Layer ID for a layer ever changes, maps and apps that reference the layer’s previous URL will break. Layer ID stability is why you must allow assignment of unique numeric IDs in an ArcGIS Pro map before publishing layers from that map.  

Exercise: Investigate a layer

  1. Open the Item Details page for the RainGaugeSites item you created earlier
  2. Click on the first layer in the Layers section
  3. Copy the URL for the REST endpoint of this layer and paste it into a private/incognito browser tab
  4. Answer these questions:
    1. How many layers does this layer item have?
    2. How does the REST endpoint URL referenced by the layer item compare to the REST endpoint referenced by first layer within that item?
    3. What is the Layer ID of the first layer?
    4. How would you prevent people from viewing the first layer without logging in?

Summary

Layer item Layer
Item ID ✔️ ❌
Layer ID ❌ ✔️
References a unique REST endpoint URL ✔️ ✔️
Sometimes called a layer ✔️ ✔️
Sometimes called a sublayer ❌ ✔️