M-values for line features do not display in ArcGIS Online pop-ups

Description

In ArcGIS Pro, clicking along an m-aware line feature displays measured values (m-values) in the pop-up. However, after the layer is published to ArcGIS Online, m-values do not appear when the feature is selected.

The ArcGIS Pro pop-up below displays the m-value when the line feature is selected.

The ArcGIS Online pop-up below does not display the m-value when the line feature is selected.

When an m-aware line layer is shared as a web layer, the following warning message is returned during publishing: 

Warning:   
24138: Layer's pop-up definition includes one or more measurement fields that are not supported online: <feature layer>

Cause

ArcGIS Online does not support measurement (m-values) stored in feature geometries. When an m-aware line layer is published as a web layer, measurement fields in the pop-up definition are not supported, and warning 24138 is returned. As a result, although the layer publishes successfully, m-values are not retained for display in ArcGIS Online pop-ups.

Solution or Workaround

Convert line feature vertices to points with X, Y, Z, and M fields before publishing

1. In ArcGIS Pro, open the project.
2. On the Analysis tab, in the Geoprocessing group, click Tools.
3. In the Geoprocessing pane, search for and select the Feature Vertices To Points (Data Management Tools) tool.
4. In the Feature Vertices To Points pane, configure the parameters as follows:
   1. For Input Features, select the line layer from the drop-down list. In this example, road_layer2 is selected.
   2. For Output Feature Class, specify the output name.
   3. For Point Type, ensure the default All vertices option is selected from the drop-down list.

4. Click Run. The output is a point feature class containing points at all vertices of the line feature.

5. In the Feature Vertices To Points pane, click Back.
6. In the Geoprocessing pane, search for and select the Add XY Coordinates (Data Management Tools) tool.
7. Use the Add XY Coordinates tool on the newly created point feature class to add the m-values for each vertex to the POINT_M field.

8. Share the layer as a web layer to ArcGIS Online. Refer to ArcGIS Pro: Publish data for more information.

Note:
Ignore the warning message and continue publishing the layer to ArcGIS Online.

9. In ArcGIS Online, navigate to Content > My content. Select the hosted feature layer to open the item details page.
10. Click the Visualization tab.
11. Click any point feature along the line feature on the map.

The pop-up below displays the m-value stored in the POINT_M field.