Map image layers come from dynamic or cached map services and can be viewed in maps and scenes. Following are some common tasks for working with map image layers.
Map image layer structure
Map image layers are added to the Contents pane as composite layers. Composite layers are expandable, so you can expand a map image layer to see its sublayers.
However, you cannot add or remove sublayers to the map image layer in the Contents pane. Since the layer is based on a map, you can view the layer's organization in the source map, but this order can't be changed. For example, you cannot insert a layer into the composite layer or divide the map image layer into its constituent sublayers. If the service includes a table, you cannot remove the table.
Get information about a map image layer
In the layer's properties, the Source tab displays information such as the map extent, server name or URL, service capabilities, cache status, and the native coordinate system of the service.
Map image layer attributions
The data source credits or attributions for an ArcGIS Server map image layer are available to display in the printed or exported map. In a map view, click the button 
located in the lower corner of the map to open a window that lists source information for all web layers currently turned on in the map. Once you export the map or create a layout, the button is replaced with the text of the web layer attributions. You cannot move or change this text.
Explore map image sublayers
Map image layers can contain one or more sublayers. The sublayer of a map service may have additional features that allow you to interact with and analyze its data.
Work with tables
If the administrator of the map service has granted permission, you can view the attribute table of a map service sublayer. Right-click a sublayer in the Contents pane and choose Attribute Table 
, or press Ctrl+T.
Map image layers can include stand-alone tables, and these tables are visible in the Contents pane. Right-click the table and choose Open to view them.
When the table is the active view, you can use the Table tab on the ribbon to perform the following tasks:
- Filter by extent
- Zoom and pan to features
- Select by attribute or location
- Create summary statistics
- Export all or a subset of features
Select attribute table and feature data
If the query capability is turned on for the map image layer, you can use the Select tool to choose multiple rows in an attribute table at a time. Selected features are highlighted in the map or scene.
In map views, creating selections on sublayer features is unchecked by default. After checking to allow selection on the Selection tab of the Contents pane, you can use selection tools to interactively select features on a map.
Note:
To see selected features, the map image layer must be published from an ArcGIS Enterprise 11.4 or later server. Earlier versions show the count of selected features but cannot draw the selection on the map. The maximum number of selected features cannot exceed the limit set by the service administrator.
View map image sublayer pop-ups
You can click map image sublayer features to open and view pop-ups. Use the Explore tool to click a feature and view its attribute information. You can only click a single feature at a time, but you can use the pop-up to zoom and pan to features. The pop-up cannot be customized, but any custom pop-ups stored with portal items in the layer are honored.
If the map image layer is configured to allow data properties, you can view the related records of the feature in the pop-up, as well.
Note:
The Flash command 
cannot be used to highlight map image layer features.
Filter features from a sublayer
If the map image sublayer is a feature layer, you can build and apply a definition query to draw a subset of features.
Right-click the feature sublayer in the Contents pane, and choose Properties 
. On the Layer Properties dialog box, click the Definition Query tab to construct a new query, set the active query, or modify an existing query.
Note:
You cannot add a spatial clause to a definition query as they are not supported.
Symbolize map image sublayers
If dynamic layers are enabled on a map service, you can modify a map image sublayer's symbology. The service must be published from ArcGIS Pro to ArcGIS Enterprise 10.9.1 or later, and must not be a cached service.
To change symbology, right-click the sublayer in the Contents pane and choose Symbology 
to open the Symbology pane. In the pane, click Modify symbology.
Similar to feature layer symbology, you can choose from a selection of primary symbology methods to change the way the data is represented. To learn how to use the Symbology pane to choose your symbology methods and settings, see Symbolize feature layers. You can also vary the sublayer's symbology by attribute to symbolize additional attributes in the data.
Note:
You cannot symbolize a map image sublayer with bivariate colors, unclassed colors, heat map, dot density, or chart symbology.
Changes to a sublayer's symbology settings are saved to the project. To return the symbology to its default (service) settings, in the Symbology pane, click the menu button and click Reset symbology to service default.
Change the display of map image layers
The Display tab in the layer's properties allows you to change the following:
- Background transparency for the web layer
- The image format used for delivering map service displays
Background transparency
All image-based services have a background. The background is any part of the image layer in which no map features are drawn. If the image type received from the server supports transparency, ArcGIS Pro makes the background transparent by default. A transparent background is particularly useful for using the layer in mash-ups (such as for point and line web layers).
To make the background color transparent, uncheck the check box in the map image layer's Display settings.
Set layer transparency
Adding transparency allows you to see map features under the layer. This adds information to the map and can add depth to your cartography. You can only add transparency to the layer, not to sublayers.
Change the web layer's image format
Many web layers can be served in a selected image format. By default, ArcGIS Pro requests images in PNG32. This format returns a high-quality image and supports transparency. However, its data size can be much larger than other formats. You can use smaller-sized formats, such as JPG; however, layer transparency is not supported for JPG.
To choose an available image format, use the Image format drop-down menu. This menu displays the format options supported by the service.
Save a map file
When you save the map or scene containing a web layer or a layer file, the web layer connection information and the state of the web layer are saved as part of the map or scene. When you reopen the map, ArcGIS Pro automatically reconnects to the server and sends an appropriate request based on the initial spatial reference, map extent, and saved state of the map layers. For example, if you turn off the visibility for a particular server layer (or its sublayers) and save the map, the layer remains turned off the next time you open the map.