I am interested in labeling features in AGO.
Is this option only available for data hosted in AGO?
I do not have the option for data within a map service or a feature service?
You can create labels for features in hosted feature layers, ArcGIS Server feature service layers, individual layers from ArcGIS Server map service layers, CSV on the web, and layers from files in the web map as outlined in this documentation: Create labels—ArcGIS Online Help | ArcGIS
You can also set labelling properties during the authouring process when building map services (cached and dynamic) outlined in this documentation. Map authoring considerations—Documentation | ArcGIS for Server
Feel free to post the web map if you are having any issues labelling a specific layer.
I must be missing something, I don't have the option to label features
It looks like this layer has been added as a map service. There are two options to get the option to have labels display for this layer:
1. Add this layer at the layer level instead of map service level. For example, add the url with the layer number: https://sampleserver6.arcgisonline.com/arcgis/rest/services/Recreation/MapServer/0 instead of https://sampleserver6.arcgisonline.com/arcgis/rest/services/Recreation/MapServer. This would then be an individual layer from ArcGIS Server map service layer and would support labels.
2. Add the labels prior to publishing the map service so that the labels can be generated by the server.
With the first option, am I able to build a cache on just the layer?
For some of our most busy maps, we need the cache for the quicker display time.
How does option 2 work with a cache?
If it is a cached map service, then you will need to use option 2, as the tiles must be created with the labels.
This documentation will help explain the authoring considerations for including labels prior to publishing/tile creation: Map authoring considerations—Documentation | ArcGIS for Server
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