Problem: The Filter Drop-down List Does Not Populate Unique Values in ArcGIS Online or Por

Description

ArcGIS Online and Portal for ArcGIS map viewers allow users to configure filters for layers based on a value, field, or unique values. Filtering based on unique values provides a drop-down list of all unique values returned by the server where the service is hosted. In some cases, when configuring filters for layers, the drop-down list is not populated.

Cause

When applying a filter, ArcGIS Online queries the server hosting the service to obtain all its necessary information. The responses from the server for the queries are based on the maxRecordCount parameter defined at the service level when publishing. By default, the maxRecordCount is set to 1000.

In some cases, the data may contain more unique values than the maxRecordCount defined in the service properties.

For example, if a service contains 3000 unique values and the maxRecordCount is not defined by the user, only the first 1000 unique values are returned.

Solution or Workaround

To resolve this issue, update the maximum record count for the affected feature services. Refer to: How To: Update the maximum record count for feature services in ArcGIS Online

Additionally, if publishing from ArcMap, the maxRecordCount can be modified in the Service Editor of ArcMap prior to publishing.

Open the Service Editor window. To access the Service Editor, refer to ArcGIS Help: Edit service properties in ArcMap.
In the Service Editor window, navigate to Parameters > Properties > Maximum number of records returned by the server.
Change the value to match the maximum number of unique values in the service.