diff --git a/api/proto/board/board_commands.proto b/api/proto/board/board_commands.proto
index 04ad03b2aa..bb5df9f425 100644
--- a/api/proto/board/board_commands.proto
+++ b/api/proto/board/board_commands.proto
@@ -24,6 +24,7 @@ package kiapi.board.commands;
 
 import "common/types/base_types.proto";
 import "common/types/enums.proto";
+import "common/types/project_settings.proto";
 import "board/board.proto";
 import "board/board_types.proto";
 
@@ -104,6 +105,22 @@ message GetItemsByNetClass
   repeated string net_classes = 3;
 }
 
+// A net may be part of multiple classes that have a priority ordering, which will result in a
+// composite "effective" netclass containing the merged/overridden properties of all the constituent
+// netclasses it contains.  This message retrieves this effective netclass for a net or list of
+// nets.
+// Returns NetClassForNetsResponse
+message GetNetClassForNets
+{
+  repeated kiapi.board.types.Net net = 1;
+}
+
+message NetClassForNetsResponse
+{
+  // Map of net name to netclass info
+  map<string, kiapi.common.project.NetClass> classes = 1;
+}
+
 /*
  * Blocking operations
  */
diff --git a/api/proto/common/types/project_settings.proto b/api/proto/common/types/project_settings.proto
index ba2796a6b2..5af1320464 100644
--- a/api/proto/common/types/project_settings.proto
+++ b/api/proto/common/types/project_settings.proto
@@ -59,15 +59,30 @@ message NetClassSchematicSettings
   optional kiapi.common.types.StrokeLineStyle line_style = 4;
 }
 
+enum NetClassType
+{
+  NCT_UNKNOWN = 0;
+  // An explicitly-defined netclass, created by the user and saved in the project file
+  NCT_EXPLICIT = 1;
+  // An implicit (effective) netclass, made up of multiple explicit netclasses
+  NCT_IMPLICIT = 2;
+}
+
 message NetClass
 {
   // The name of the netclass (the literal string "Default" for the default netclass)
+  // May be empty for composite netclasses
   string name = 1;
 
   optional int32 priority = 2;
 
   optional NetClassBoardSettings board = 3;
   optional NetClassSchematicSettings schematic = 4;
+
+  NetClassType type = 5;
+
+  // If this is a composite netclass, a list of the names of the "real" netclasses that make it up
+  repeated string constituents = 6;
 }
 
 message TextVariables
diff --git a/common/netclass.cpp b/common/netclass.cpp
index e9583f5900..335bbf2328 100644
--- a/common/netclass.cpp
+++ b/common/netclass.cpp
@@ -137,6 +137,11 @@ void NETCLASS::Serialize( google::protobuf::Any &aContainer ) const
     nc.set_name( m_Name.ToUTF8() );
     nc.set_priority( m_Priority );
 
+    nc.set_type( m_constituents.empty() ? project::NCT_EXPLICIT : project::NCT_IMPLICIT );
+
+    for( NETCLASS* member : m_constituents )
+        nc.add_constituents( member->GetName() );
+
     project::NetClassBoardSettings* board = nc.mutable_board();
 
     if( m_Clearance )
@@ -204,6 +209,12 @@ bool NETCLASS::Deserialize( const google::protobuf::Any &aContainer )
     m_Name = wxString::FromUTF8( nc.name() );
     m_Priority = nc.priority();
 
+    // We don't allow creating implicit classes directly
+    if( nc.type() == project::NCT_IMPLICIT )
+        return false;
+
+    SetConstituentNetclasses( {} );
+
     if( nc.board().has_clearance() )
         m_Clearance = nc.board().clearance().value_nm();
 
diff --git a/pcbnew/api/api_handler_pcb.cpp b/pcbnew/api/api_handler_pcb.cpp
index e8142bfe3a..f8179fb076 100644
--- a/pcbnew/api/api_handler_pcb.cpp
+++ b/pcbnew/api/api_handler_pcb.cpp
@@ -76,6 +76,8 @@ API_HANDLER_PCB::API_HANDLER_PCB( PCB_EDIT_FRAME* aFrame ) :
 
     registerHandler<InteractiveMoveItems, Empty>( &API_HANDLER_PCB::handleInteractiveMoveItems );
     registerHandler<GetNets, NetsResponse>( &API_HANDLER_PCB::handleGetNets );
+    registerHandler<GetNetClassForNets, NetClassForNetsResponse>(
+            &API_HANDLER_PCB::handleGetNetClassForNets );
     registerHandler<RefillZones, Empty>( &API_HANDLER_PCB::handleRefillZones );
 
     registerHandler<SaveDocumentToString, SavedDocumentResponse>(
@@ -830,6 +832,31 @@ HANDLER_RESULT<NetsResponse> API_HANDLER_PCB::handleGetNets( const HANDLER_CONTE
 }
 
 
+HANDLER_RESULT<NetClassForNetsResponse> API_HANDLER_PCB::handleGetNetClassForNets(
+            const HANDLER_CONTEXT<GetNetClassForNets>& aCtx )
+{
+    NetClassForNetsResponse response;
+
+    BOARD* board = frame()->GetBoard();
+    NETINFO_LIST nets = board->GetNetInfo();
+    google::protobuf::Any any;
+
+    for( const board::types::Net& net : aCtx.Request.net() )
+    {
+        NETINFO_ITEM* netInfo = nets.GetNetItem( wxString::FromUTF8( net.name() ) );
+
+        if( !netInfo )
+            continue;
+
+        netInfo->GetNetClass()->Serialize( any );
+        auto [pair, rc] = response.mutable_classes()->insert( { net.name(), {} } );
+        any.UnpackTo( &pair->second );
+    }
+
+    return response;
+}
+
+
 HANDLER_RESULT<Empty> API_HANDLER_PCB::handleRefillZones( const HANDLER_CONTEXT<RefillZones>& aCtx )
 {
     if( std::optional<ApiResponseStatus> busy = checkForBusy() )
diff --git a/pcbnew/api/api_handler_pcb.h b/pcbnew/api/api_handler_pcb.h
index 80c9ed6458..618154fec7 100644
--- a/pcbnew/api/api_handler_pcb.h
+++ b/pcbnew/api/api_handler_pcb.h
@@ -87,6 +87,9 @@ private:
 
     HANDLER_RESULT<NetsResponse> handleGetNets( const HANDLER_CONTEXT<GetNets>& aCtx );
 
+    HANDLER_RESULT<NetClassForNetsResponse> handleGetNetClassForNets(
+            const HANDLER_CONTEXT<GetNetClassForNets>& aCtx );
+
     HANDLER_RESULT<Empty> handleRefillZones( const HANDLER_CONTEXT<RefillZones>& aCtx );
 
     HANDLER_RESULT<commands::SavedDocumentResponse> handleSaveDocumentToString(