Current capabilities of 4.4

• Displaying maps in both 2D and 3D
• Load web maps in 2D applications, see FAQ for more info.
• Easily use web scenes in 3D applications
• Map rotation
• Support for specifying basemaps by name, like streets, including the new vector tile basemaps
• Support for many different layer types: ElevationLayer, FeatureLayer, ImageryLayer, MapImageLayer , TileLayer, VectorTileLayer, GeoRSSLayer, GraphicsLayer, OpenStreetMapLayer, SceneLayer, StreamLayer and WebTileLayer. Note that some layer types don't yet have all the capabilites of the same layer in 3.x.
• Ability to group layers using the new GroupLayer class
• Renderers and symbols to create great visualizations in 2D and 3D
• Client-side geometry engine
• Several widgets
  • Attribution
  • BasemapToggle
  • Compass
  • Home
  • Legend - only supports FeatureLayer at 4.0
  • Locate
  • Search
  • Track
  • Zoom
• Working directly with network analyst related tasks for routing ClosestFacilityTask, Locator, RouteTask and ServiceAreaTask.
• Querying ArcGIS Server using FindTask, GeometryService, IdentifyTask, ImageServiceIdentifyTask and QueryTask.
• Support for execting geoprocessing tasks

For more details, please refer to the 4.4 API Reference.

Planned capabilities for 4.x releases

This is functionality that is planned for upcoming versions of 4.x, but that are not part of the 4.4 release.

• Editing
• Draw and edit tools
• Temporal awareness: rendering and filtering
• Writing web maps
• GeoEnrichment
• Extensions for Operations dashboard
• DataReviewer tasks
• More layer types: KMLLayer, WMSLayer and WMTSLayer
• More renderers: dot density, heatmaps, scale dependent and temporal
• More widgets: Directions, FeatureTable, OverviewMap, analysis widgets etc.
• Legend widget: support for all layer types

See also system requirements for supported browsers.