diff --git a/Microsoft.ML.sln b/Microsoft.ML.sln
index 6b0b880210..c9aae84314 100644
--- a/Microsoft.ML.sln
+++ b/Microsoft.ML.sln
@@ -274,6 +274,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Microsoft.ML.FastTree", "Mi
 		pkg\Microsoft.ML.FastTree\Microsoft.ML.FastTree.symbols.nupkgproj = pkg\Microsoft.ML.FastTree\Microsoft.ML.FastTree.symbols.nupkgproj
 	EndProjectSection
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.ML.StableApi", "tools-local\Microsoft.ML.StableApi\Microsoft.ML.StableApi.csproj", "{F308DC6B-7E59-40D7-A581-834E8CD99CFE}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -968,6 +970,18 @@ Global
 		{E02DA82D-3FEE-4C60-BD80-9EC3C3448DFC}.Release-Intrinsics|Any CPU.Build.0 = Release-Intrinsics|Any CPU
 		{E02DA82D-3FEE-4C60-BD80-9EC3C3448DFC}.Release-netfx|Any CPU.ActiveCfg = Release-netfx|Any CPU
 		{E02DA82D-3FEE-4C60-BD80-9EC3C3448DFC}.Release-netfx|Any CPU.Build.0 = Release-netfx|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Debug-Intrinsics|Any CPU.ActiveCfg = Debug-Intrinsics|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Debug-Intrinsics|Any CPU.Build.0 = Debug-Intrinsics|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Debug-netfx|Any CPU.ActiveCfg = Debug-netfx|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Debug-netfx|Any CPU.Build.0 = Debug-netfx|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Release|Any CPU.Build.0 = Release|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Release-Intrinsics|Any CPU.ActiveCfg = Release-Intrinsics|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Release-Intrinsics|Any CPU.Build.0 = Release-Intrinsics|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Release-netfx|Any CPU.ActiveCfg = Release-netfx|Any CPU
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE}.Release-netfx|Any CPU.Build.0 = Release-netfx|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -1055,6 +1069,7 @@ Global
 		{AD7058C9-5608-49A8-BE23-58C33A74EE91} = {D3D38B03-B557-484D-8348-8BADEE4DF592}
 		{E02DA82D-3FEE-4C60-BD80-9EC3C3448DFC} = {09EADF06-BE25-4228-AB53-95AE3E15B530}
 		{B1B3F284-FA3D-4D76-A712-FF04495D244B} = {D3D38B03-B557-484D-8348-8BADEE4DF592}
+		{F308DC6B-7E59-40D7-A581-834E8CD99CFE} = {7F13E156-3EBA-4021-84A5-CD56BA72F99E}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {41165AF1-35BB-4832-A189-73060F82B01D}
diff --git a/build/Dependencies.props b/build/Dependencies.props
index 17f25a17a3..963fecead7 100644
--- a/build/Dependencies.props
+++ b/build/Dependencies.props
@@ -36,6 +36,7 @@
     <CodecovVersion>1.1.1</CodecovVersion>
     <CoverletVersion>2.6.0</CoverletVersion>
     <ReportGeneratorVersion>4.0.9</ReportGeneratorVersion>
+    <MicrosoftDotNetApiCompatPackageVersion>1.0.0-beta.19225.5</MicrosoftDotNetApiCompatPackageVersion>
   </PropertyGroup>
 
   <!-- Test-only Dependencies -->
diff --git a/src/Directory.Build.props b/src/Directory.Build.props
index be6d1d53bc..f7ef5ae42b 100644
--- a/src/Directory.Build.props
+++ b/src/Directory.Build.props
@@ -21,6 +21,19 @@
     <PackageRid>$(PackageRid)-$(TargetArchitecture)</PackageRid>
   </PropertyGroup>
 
+<!-- API Compat -->
+  <PropertyGroup>
+    <RunApiCompat Condition="'$(RunApiCompat)' == ''">$(IsStableProject)</RunApiCompat>
+    <ToolHostCmd Condition="'$(OS)' != 'Windows_NT'">$(ToolsDir)dotnetcli/dotnet</ToolHostCmd>
+
+
+    <!-- only validate that the current implementation is compatible
+         with the old one, not vice-versa (since latest may have new
+         API missing from old) -->
+    <RunApiCompatForSrc>true</RunApiCompatForSrc>
+    <RunMatchingRefApiCompat>false</RunMatchingRefApiCompat>
+  </PropertyGroup>
+  
   <ItemGroup>
     <ProjectReference
       Condition="'$(UseMLCodeAnalyzer)' != 'false' and '$(MSBuildProjectExtension)' == '.csproj'"
@@ -37,5 +50,4 @@
       <Link>stylecop.json</Link>
     </AdditionalFiles>
   </ItemGroup>
-
 </Project>
diff --git a/src/Directory.Build.targets b/src/Directory.Build.targets
index 2c6ae691d4..28c54362df 100644
--- a/src/Directory.Build.targets
+++ b/src/Directory.Build.targets
@@ -26,4 +26,32 @@
 
   </Target>
 
+  <!-- API Compat -->
+  <PropertyGroup Condition="'$(RunApiCompat)' == 'true'">
+    <!-- resolve contract for APICompat as part of resolve references -->
+    <ResolveReferencesDependsOn>
+      $(ResolveReferencesDependsOn);
+      ResolveMatchingContract
+    </ResolveReferencesDependsOn>
+
+    <StableApiProject>$(RepoRoot)tools-local\Microsoft.ML.StableApi\Microsoft.ML.StableApi.csproj</StableApiProject>
+  </PropertyGroup>
+
+  <ItemGroup Condition="'$(RunApiCompat)' == 'true'">
+    <PackageReference Include="Microsoft.DotNet.ApiCompat"
+                      Version="$(MicrosoftDotNetApiCompatPackageVersion)"
+                      PrivateAssets="All" />
+  </ItemGroup>
+
+  <Target Name="ResolveMatchingContract">
+    <MSBuild Projects="$(StableApiProject)"
+             Targets="GetContract"
+             Properties="ContractName=$(AssemblyName);TargetFramework=$(TargetFramework)">
+      <Output TaskParameter="TargetOutputs" ItemName="ResolvedMatchingContract"/>
+    </MSBuild>
+    <PropertyGroup>
+      <ContractOutputPath>%(ResolvedMatchingContract.DependencyPaths)</ContractOutputPath>
+    </PropertyGroup>
+  </Target>
+
 </Project>
diff --git a/tools-local/Microsoft.ML.StableApi/Microsoft.ML.StableApi.csproj b/tools-local/Microsoft.ML.StableApi/Microsoft.ML.StableApi.csproj
new file mode 100644
index 0000000000..e1b569a026
--- /dev/null
+++ b/tools-local/Microsoft.ML.StableApi/Microsoft.ML.StableApi.csproj
@@ -0,0 +1,45 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <!-- needs to contain all frameworks which src projects wish to restore -->
+    <TargetFramework Condition="'$(UseIntrinsics)' != 'true'">netstandard2.0</TargetFramework>
+    <TargetFrameworks Condition="'$(UseIntrinsics)' == 'true'">netstandard2.0;netcoreapp3.0</TargetFrameworks>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.ML" Version="1.0.0" />
+    <PackageReference Include="Microsoft.ML.DataView" Version="1.0.0" />
+    <PackageReference Include="Microsoft.ML.CpuMath" Version="1.0.0" />
+    <PackageReference Include="Microsoft.ML.FastTree" Version="1.0.0" />
+    <PackageReference Include="Microsoft.ML.LightGbm" Version="1.0.0" />
+    <PackageReference Include="Microsoft.ML.ImageAnalytics" Version="1.0.0" />
+    <PackageReference Include="Microsoft.ML.Mkl.Components" Version="1.0.0" />
+  </ItemGroup>
+
+  <!-- The purpose of this target is to return a path from a referenced
+       package / project -->
+  <Target Name="GetContract" DependsOnTargets="ResolveReferences" Returns="@(_contractReferencePath)">
+    <Error Condition="'$(ContractName)' == ''" Text="ContractName must be specified" />
+    <ItemGroup>
+      <_contractReferencePath Include="@(ReferencePath)" Condition="'%(FileName)' == '$(ContractName)'" />
+      <_allReferenceDirectories Include="%(ReferencePath.RootDir)%(ReferencePath.Directory)" />
+      <_contractReferencePath Include="@(ReferencePath)" Condition="'%(FileName)' == '$(ContractName)'" />
+      <_contractReferencePath DependencyPaths="@(_allReferenceDirectories)" />
+    </ItemGroup>
+    <Error Condition="'@(_contractReferencePath)' == ''" Text="Could not locate $(ContractName)" />
+  </Target>
+
+  <Target Name="Build">
+    <!-- This will override the default Build target. -->
+  </Target>
+  <Target Name="Rebuild">
+    <!-- This will override the default Rebuild target. -->
+  </Target>
+  <Target Name="BuildAndTest">
+    <!-- This will override the default BuildAndTest target. -->
+  </Target>
+  <Target Name="RebuildAndTest">
+    <!-- This will override the default RebuildAndTest target. -->
+  </Target>
+
+</Project>