diff --git a/.azure-pipelines/ci.yml b/.azure-pipelines/ci.yml
index fe10e45..4c2f115 100644
--- a/.azure-pipelines/ci.yml
+++ b/.azure-pipelines/ci.yml
@@ -145,7 +145,7 @@
         buildOpt: '-p x64'
         testRunTitle: '$(Build.SourceBranchName)-win64'
         testRunPlatform: win64
-    maxParallel: 2
+    maxParallel: 4
 
   steps:
   - template: ./windows-steps.yml
diff --git a/.azure-pipelines/pr.yml b/.azure-pipelines/pr.yml
index 09209fc..73d4f55 100644
--- a/.azure-pipelines/pr.yml
+++ b/.azure-pipelines/pr.yml
@@ -145,7 +145,10 @@
         buildOpt: '-p x64'
         testRunTitle: '$(System.PullRequest.TargetBranch)-win64'
         testRunPlatform: win64
-    maxParallel: 2
+      winarm64:
+        arch: arm64
+        buildOpt: '-p arm64'
+    maxParallel: 4
 
   steps:
   - template: ./windows-steps.yml
diff --git a/.azure-pipelines/windows-release/build-steps.yml b/.azure-pipelines/windows-release/build-steps.yml
index d4563cd..e2b6683 100644
--- a/.azure-pipelines/windows-release/build-steps.yml
+++ b/.azure-pipelines/windows-release/build-steps.yml
@@ -43,7 +43,7 @@
 
 - powershell: |
     $env:SigningCertificate = $null
-    .\python.bat PC\layout -vv -t "$(Build.BinariesDirectory)\catalog" --catalog "${env:CAT}.cdf" --preset-default
+    python PC\layout -vv -b "$(Build.BinariesDirectory)\bin" -t "$(Build.BinariesDirectory)\catalog" --catalog "${env:CAT}.cdf" --preset-default --arch $(Arch)
     makecat "${env:CAT}.cdf"
     del "${env:CAT}.cdf"
     if (-not (Test-Path "${env:CAT}.cat")) {
@@ -52,6 +52,7 @@
   displayName: 'Generate catalog'
   env:
     CAT: $(Build.BinariesDirectory)\bin\$(Arch)\python
+    PYTHON_HEXVERSION: $(VersionHex)
 
 - task: PublishPipelineArtifact@0
   displayName: 'Publish binaries'
diff --git a/.azure-pipelines/windows-release/layout-command.yml b/.azure-pipelines/windows-release/layout-command.yml
index 2dcd6ed..406ccd8 100644
--- a/.azure-pipelines/windows-release/layout-command.yml
+++ b/.azure-pipelines/windows-release/layout-command.yml
@@ -1,12 +1,20 @@
 steps:
+- task: DownloadPipelineArtifact@1
+  displayName: 'Download artifact: bin_$(HostArch)'
+  condition: and(succeeded(), variables['HostArch'])
+  inputs:
+    artifactName: bin_$(HostArch)
+    targetPath: $(Build.BinariesDirectory)\bin_$(HostArch)
+
 - powershell: >
     Write-Host (
     '##vso[task.setvariable variable=LayoutCmd]&
-    "{0}\bin\python.exe"
+    "$(Python)"
     "{1}\PC\layout"
     -vv
     --source "{1}"
     --build "{0}\bin"
+    --arch "$(Name)"
     --temp "{0}\layout-temp"
     --include-cat "{0}\bin\python.cat"
     --doc-build "{0}\doc"'
diff --git a/.azure-pipelines/windows-release/msi-steps.yml b/.azure-pipelines/windows-release/msi-steps.yml
index f7bff16..a460eb1 100644
--- a/.azure-pipelines/windows-release/msi-steps.yml
+++ b/.azure-pipelines/windows-release/msi-steps.yml
@@ -54,6 +54,7 @@
   - powershell: |
       copy $(Build.BinariesDirectory)\amd64\Activate.ps1 Lib\venv\scripts\common\Activate.ps1 -Force
     displayName: 'Copy signed files into sources'
+    condition: and(succeeded(), variables['SigningCertificate'])
 
   - script: |
       call Tools\msi\get_externals.bat
diff --git a/.azure-pipelines/windows-release/stage-build.yml b/.azure-pipelines/windows-release/stage-build.yml
index c98576e..60d72b2 100644
--- a/.azure-pipelines/windows-release/stage-build.yml
+++ b/.azure-pipelines/windows-release/stage-build.yml
@@ -16,14 +16,16 @@
     env:
       BUILDDIR: $(Build.BinariesDirectory)\Doc
 
-  #- powershell: iwr "https://www.python.org/ftp/python/3.7.3/python373.chm" -OutFile "$(Build.BinariesDirectory)\python390a0.chm"
-  #  displayName: 'Cheat at building CHM docs'
-
   - script: Doc\make.bat htmlhelp
     displayName: 'Build CHM docs'
     env:
       BUILDDIR: $(Build.BinariesDirectory)\Doc
 
+  #- powershell: |
+  #    mkdir -Force "$(Build.BinariesDirectory)\Doc\htmlhelp"
+  #    iwr "https://www.python.org/ftp/python/3.8.0/python380.chm" -OutFile "$(Build.BinariesDirectory)\Doc\htmlhelp\python390a0.chm"
+  #  displayName: 'Cheat at building CHM docs'
+
   - task: CopyFiles@2
     displayName: 'Assemble artifact: Doc'
     inputs:
@@ -65,6 +67,16 @@
         Arch: amd64
         Platform: x64
         Configuration: Debug
+      arm64:
+        Name: arm64
+        Arch: arm64
+        Platform: ARM64
+        Configuration: Release
+      arm64_d:
+        Name: arm64_d
+        Arch: arm64
+        Platform: ARM64
+        Configuration: Debug
 
   steps:
     - template: ./build-steps.yml
diff --git a/.azure-pipelines/windows-release/stage-layout-embed.yml b/.azure-pipelines/windows-release/stage-layout-embed.yml
index 09857ff..3306e1c 100644
--- a/.azure-pipelines/windows-release/stage-layout-embed.yml
+++ b/.azure-pipelines/windows-release/stage-layout-embed.yml
@@ -19,6 +19,11 @@
         Name: amd64
         Python: $(Build.BinariesDirectory)\bin\python.exe
         PYTHONHOME: $(Build.SourcesDirectory)
+      arm64:
+        Name: arm64
+        HostArch: amd64
+        Python: $(Build.BinariesDirectory)\bin_amd64\python.exe
+        PYTHONHOME: $(Build.SourcesDirectory)
 
   steps:
   - template: ./checkout.yml
diff --git a/.azure-pipelines/windows-release/stage-layout-full.yml b/.azure-pipelines/windows-release/stage-layout-full.yml
index 12c3472..78bc1b3 100644
--- a/.azure-pipelines/windows-release/stage-layout-full.yml
+++ b/.azure-pipelines/windows-release/stage-layout-full.yml
@@ -13,11 +13,18 @@
     matrix:
       win32:
         Name: win32
-        Python: $(Build.BinariesDirectory)\bin_$(Name)\python.exe
+        Python: $(Build.BinariesDirectory)\bin\python.exe
         PYTHONHOME: $(Build.SourcesDirectory)
+        TclLibrary: $(Build.BinariesDirectory)\tcltk_lib\tcl8
       amd64:
         Name: amd64
-        Python: $(Build.BinariesDirectory)\bin_$(Name)\python.exe
+        Python: $(Build.BinariesDirectory)\bin\python.exe
+        PYTHONHOME: $(Build.SourcesDirectory)
+        TclLibrary: $(Build.BinariesDirectory)\tcltk_lib\tcl8
+      arm64:
+        Name: arm64
+        HostArch: amd64
+        Python: $(Build.BinariesDirectory)\bin_amd64\python.exe
         PYTHONHOME: $(Build.SourcesDirectory)
 
   steps:
@@ -43,13 +50,15 @@
 
   - task: DownloadPipelineArtifact@1
     displayName: 'Download artifact: tcltk_lib_$(Name)'
+    condition: and(succeeded(), variables['TclLibrary'])
     inputs:
       artifactName: tcltk_lib_$(Name)
       targetPath: $(Build.BinariesDirectory)\tcltk_lib
 
   - powershell: |
-      copy $(Build.BinariesDirectory)\bin\Activate.ps1 Lib\venv\scripts\common\Activate.ps1 -Force
+      copy "$(Build.BinariesDirectory)\bin\Activate.ps1" Lib\venv\scripts\common\Activate.ps1 -Force
     displayName: 'Copy signed files into sources'
+    condition: and(succeeded(), variables['SigningCertificate'])
 
   - template: ./layout-command.yml
 
@@ -57,7 +66,7 @@
       $(LayoutCmd) --copy "$(Build.ArtifactStagingDirectory)\layout" --preset-default
     displayName: 'Generate full layout'
     env:
-      TCL_LIBRARY: $(Build.BinariesDirectory)\tcltk_lib\tcl8
+      TCL_LIBRARY: $(TclLibrary)
 
   - task: PublishPipelineArtifact@0
     displayName: 'Publish Artifact: layout_full_$(Name)'
diff --git a/.azure-pipelines/windows-release/stage-layout-msix.yml b/.azure-pipelines/windows-release/stage-layout-msix.yml
index ba86392..60a5c9e 100644
--- a/.azure-pipelines/windows-release/stage-layout-msix.yml
+++ b/.azure-pipelines/windows-release/stage-layout-msix.yml
@@ -12,11 +12,18 @@
     matrix:
       #win32:
       #  Name: win32
-      #  Python: $(Build.BinariesDirectory)\bin_$(Name)\python.exe
+      #  Python: $(Build.BinariesDirectory)\bin\python.exe
       #  PYTHONHOME: $(Build.SourcesDirectory)
+      #  TclLibrary: $(Build.BinariesDirectory)\tcltk_lib\tcl8
       amd64:
         Name: amd64
-        Python: $(Build.BinariesDirectory)\bin_$(Name)\python.exe
+        Python: $(Build.BinariesDirectory)\bin\python.exe
+        PYTHONHOME: $(Build.SourcesDirectory)
+        TclLibrary: $(Build.BinariesDirectory)\tcltk_lib\tcl8
+      arm64:
+        Name: arm64
+        HostArch: amd64
+        Python: $(Build.BinariesDirectory)\bin_amd64\python.exe
         PYTHONHOME: $(Build.SourcesDirectory)
 
   steps:
@@ -36,13 +43,15 @@
 
   - task: DownloadPipelineArtifact@1
     displayName: 'Download artifact: tcltk_lib_$(Name)'
+    condition: and(succeeded(), variables['TclLibrary'])
     inputs:
       artifactName: tcltk_lib_$(Name)
       targetPath: $(Build.BinariesDirectory)\tcltk_lib
 
   - powershell: |
-      copy $(Build.BinariesDirectory)\bin\Activate.ps1 Lib\venv\scripts\common\Activate.ps1 -Force
+      copy "$(Build.BinariesDirectory)\bin\Activate.ps1" Lib\venv\scripts\common\Activate.ps1 -Force
     displayName: 'Copy signed files into sources'
+    condition: and(succeeded(), variables['SigningCertificate'])
 
   - template: ./layout-command.yml
 
@@ -51,7 +60,7 @@
       $(LayoutCmd) --copy "$(Build.ArtifactStagingDirectory)\appx-store" --preset-appx --precompile
     displayName: 'Generate store APPX layout'
     env:
-      TCL_LIBRARY: $(Build.BinariesDirectory)\tcltk_lib\tcl8
+      TCL_LIBRARY: $(TclLibrary)
 
   - task: PublishPipelineArtifact@0
     displayName: 'Publish Artifact: layout_appxstore_$(Name)'
@@ -79,7 +88,7 @@
       $(LayoutCmd) --copy "$(Build.ArtifactStagingDirectory)\appx" --preset-appx --precompile --include-symbols --include-tests
     displayName: 'Generate sideloading APPX layout'
     env:
-      TCL_LIBRARY: $(Build.BinariesDirectory)\tcltk_lib\tcl8
+      TCL_LIBRARY: $(TclLibrary)
 
   - task: PublishPipelineArtifact@0
     displayName: 'Publish Artifact: layout_appx_$(Name)'
diff --git a/.azure-pipelines/windows-release/stage-layout-nuget.yml b/.azure-pipelines/windows-release/stage-layout-nuget.yml
index 7954c45..7e20f89 100644
--- a/.azure-pipelines/windows-release/stage-layout-nuget.yml
+++ b/.azure-pipelines/windows-release/stage-layout-nuget.yml
@@ -13,11 +13,16 @@
     matrix:
       win32:
         Name: win32
-        Python: $(Build.BinariesDirectory)\bin_$(Name)\python.exe
+        Python: $(Build.BinariesDirectory)\bin\python.exe
         PYTHONHOME: $(Build.SourcesDirectory)
       amd64:
         Name: amd64
-        Python: $(Build.BinariesDirectory)\bin_$(Name)\python.exe
+        Python: $(Build.BinariesDirectory)\bin\python.exe
+        PYTHONHOME: $(Build.SourcesDirectory)
+      arm64:
+        Name: arm64
+        HostArch: amd64
+        Python: $(Build.BinariesDirectory)\bin_amd64\python.exe
         PYTHONHOME: $(Build.SourcesDirectory)
 
   steps:
@@ -32,14 +37,13 @@
   - powershell: |
       copy $(Build.BinariesDirectory)\bin\Activate.ps1 Lib\venv\scripts\common\Activate.ps1 -Force
     displayName: 'Copy signed files into sources'
+    condition: and(succeeded(), variables['SigningCertificate'])
 
   - template: ./layout-command.yml
 
   - powershell: |
       $(LayoutCmd) --copy "$(Build.ArtifactStagingDirectory)\nuget" --preset-nuget
     displayName: 'Generate nuget layout'
-    env:
-      TCL_LIBRARY: $(Build.BinariesDirectory)\bin_$(Name)\tcl\tcl8
 
   - task: PublishPipelineArtifact@0
     displayName: 'Publish Artifact: layout_nuget_$(Name)'
diff --git a/.azure-pipelines/windows-release/stage-pack-msix.yml b/.azure-pipelines/windows-release/stage-pack-msix.yml
index eebc63f..f17ba96 100644
--- a/.azure-pipelines/windows-release/stage-pack-msix.yml
+++ b/.azure-pipelines/windows-release/stage-pack-msix.yml
@@ -20,6 +20,16 @@
         Artifact: appxstore
         Suffix: -store
         Upload: true
+      arm64:
+        Name: arm64
+        Artifact: appx
+        Suffix:
+        ShouldSign: true
+      arm64_store:
+        Name: arm64
+        Artifact: appxstore
+        Suffix: -store
+        Upload: true
 
   steps:
   - template: ./checkout.yml
diff --git a/.azure-pipelines/windows-release/stage-pack-nuget.yml b/.azure-pipelines/windows-release/stage-pack-nuget.yml
index f59bbe9..34619fc 100644
--- a/.azure-pipelines/windows-release/stage-pack-nuget.yml
+++ b/.azure-pipelines/windows-release/stage-pack-nuget.yml
@@ -15,6 +15,8 @@
         Name: amd64
       win32:
         Name: win32
+      arm64:
+        Name: arm64
 
   steps:
   - checkout: none
diff --git a/.azure-pipelines/windows-release/stage-publish-nugetorg.yml b/.azure-pipelines/windows-release/stage-publish-nugetorg.yml
index 570cdb3..b78bd49 100644
--- a/.azure-pipelines/windows-release/stage-publish-nugetorg.yml
+++ b/.azure-pipelines/windows-release/stage-publish-nugetorg.yml
@@ -31,6 +31,11 @@
       buildVersionToDownload: specific
       buildId: $(BuildToPublish)
 
+  - powershell: 'gci pythonarm*.nupkg | %{ Write-Host "Not publishing: $($_.Name)"; gi $_ } | del'
+    displayName: 'Prevent publishing ARM/ARM64 packages'
+    workingDirectory: '$(Build.BinariesDirectory)\nuget'
+    condition: and(succeeded(), not(variables['PublishArmPackages']))
+
   - task: NuGetCommand@2
     displayName: Push packages
     condition: and(succeeded(), eq(variables['SigningCertificate'], variables['__RealSigningCertificate']))
diff --git a/.azure-pipelines/windows-release/stage-publish-pythonorg.yml b/.azure-pipelines/windows-release/stage-publish-pythonorg.yml
index 2dd354a..8c95f1b 100644
--- a/.azure-pipelines/windows-release/stage-publish-pythonorg.yml
+++ b/.azure-pipelines/windows-release/stage-publish-pythonorg.yml
@@ -39,6 +39,10 @@
       artifactName: embed
       downloadPath: $(Build.BinariesDirectory)
 
+  - powershell: 'gci *embed-arm*.zip | %{ Write-Host "Not publishing: $($_.Name)"; gi $_ } | del'
+    displayName: 'Prevent publishing ARM/ARM64 packages'
+    workingDirectory: '$(Build.BinariesDirectory)\embed'
+    condition: and(succeeded(), not(variables['PublishArmPackages']))
 
   - task: DownloadPipelineArtifact@1
     displayName: 'Download artifact from $(BuildToPublish): Doc'
diff --git a/.azure-pipelines/windows-release/stage-sign.yml b/.azure-pipelines/windows-release/stage-sign.yml
index 2307c6c..a0adc05 100644
--- a/.azure-pipelines/windows-release/stage-sign.yml
+++ b/.azure-pipelines/windows-release/stage-sign.yml
@@ -19,6 +19,8 @@
         Name: win32
       amd64:
         Name: amd64
+      arm64:
+        Name: arm64
 
   steps:
   - template: ./checkout.yml
diff --git a/.azure-pipelines/windows-steps.yml b/.azure-pipelines/windows-steps.yml
index 794a23a..f502c40 100644
--- a/.azure-pipelines/windows-steps.yml
+++ b/.azure-pipelines/windows-steps.yml
@@ -19,9 +19,11 @@
 
 - script: python.bat -m test.pythoninfo
   displayName: 'Display build info'
+  condition: and(succeeded(), variables['testRunPlatform'])
 
 - script: PCbuild\rt.bat -q -uall -u-cpu -rwW --slowest --timeout=1200 -j0 --junit-xml="$(Build.BinariesDirectory)\test-results.xml" --tempdir="$(Build.BinariesDirectory)\test"
   displayName: 'Tests'
+  condition: and(succeeded(), variables['testRunPlatform'])
   env:
     PREFIX: $(Py_OutDir)\$(arch)
 
@@ -32,4 +34,4 @@
     mergeTestResults: true
     testRunTitle: $(testRunTitle)
     platform: $(testRunPlatform)
-  condition: succeededOrFailed()
+  condition: and(succeededOrFailed(), variables['testRunPlatform'])
diff --git a/Misc/NEWS.d/next/Windows/2019-11-14-08-57-50.bpo-33125.EN5MWS.rst b/Misc/NEWS.d/next/Windows/2019-11-14-08-57-50.bpo-33125.EN5MWS.rst
new file mode 100644
index 0000000..0bc98c1
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2019-11-14-08-57-50.bpo-33125.EN5MWS.rst
@@ -0,0 +1 @@
+Add support for building and releasing Windows ARM64 packages.
diff --git a/PC/layout/main.py b/PC/layout/main.py
index 3ca49d0..305cb51 100644
--- a/PC/layout/main.py
+++ b/PC/layout/main.py
@@ -285,14 +285,13 @@
         log_warning("Failed to compile {}", src)
         return None
 
+
 # name argument added to address bpo-37641
 def _py_temp_compile(src, name, ns, dest_dir=None, checked=True):
     if not ns.precompile or src not in PY_FILES or src.parent in DATA_DIRS:
         return None
     dest = (dest_dir or ns.temp) / (src.stem + ".pyc")
-    return _compile_one_py(
-        src, dest, name, optimize=2, checked=checked
-    )
+    return _compile_one_py(src, dest, name, optimize=2, checked=checked)
 
 
 def _write_to_zip(zf, dest, src, ns, checked=True):
@@ -497,6 +496,13 @@
         "-b", "--build", metavar="dir", help="Specify the build directory", type=Path
     )
     parser.add_argument(
+        "--arch",
+        metavar="architecture",
+        help="Specify the target architecture",
+        type=str,
+        default=None,
+    )
+    parser.add_argument(
         "--doc-build",
         metavar="dir",
         help="Specify the docs build directory",
@@ -587,6 +593,8 @@
         ns.doc_build = (Path.cwd() / ns.doc_build).resolve()
     if ns.include_cat and not ns.include_cat.is_absolute():
         ns.include_cat = (Path.cwd() / ns.include_cat).resolve()
+    if not ns.arch:
+        ns.arch = "amd64" if sys.maxsize > 2 ** 32 else "win32"
 
     if ns.copy and not ns.copy.is_absolute():
         ns.copy = (Path.cwd() / ns.copy).resolve()
@@ -602,6 +610,7 @@
 Source: {ns.source}
 Build:  {ns.build}
 Temp:   {ns.temp}
+Arch:   {ns.arch}
 
 Copy to: {ns.copy}
 Zip to:  {ns.zip}
@@ -609,6 +618,15 @@
         ns=ns,
     )
 
+    if ns.arch not in ("win32", "amd64", "arm32", "arm64"):
+        log_error("--arch is not a valid value (win32, amd64, arm32, arm64)")
+        return 4
+    if ns.arch in ("arm32", "arm64"):
+        for n in ("include_idle", "include_tcltk"):
+            if getattr(ns, n):
+                log_warning(f"Disabling --{n.replace('_', '-')} on unsupported platform")
+                setattr(ns, n, False)
+
     if ns.include_idle and not ns.include_tcltk:
         log_warning("Assuming --include-tcltk to support --include-idle")
         ns.include_tcltk = True
diff --git a/PC/layout/support/appxmanifest.py b/PC/layout/support/appxmanifest.py
index de5813a..9e008f7 100644
--- a/PC/layout/support/appxmanifest.py
+++ b/PC/layout/support/appxmanifest.py
@@ -28,7 +28,14 @@
     ),
     DisplayName="Python {}".format(VER_DOT),
     Description="The Python {} runtime and console.".format(VER_DOT),
-    ProcessorArchitecture="x64" if IS_X64 else "x86",
+)
+
+APPX_PLATFORM_DATA = dict(
+    _keys=("ProcessorArchitecture",),
+    win32=("x86",),
+    amd64=("x64",),
+    arm32=("arm",),
+    arm64=("arm64",),
 )
 
 PYTHON_VE_DATA = dict(
@@ -65,7 +72,7 @@
     BackgroundColor="transparent",
 )
 
-PY_PNG = '_resources/py.png'
+PY_PNG = "_resources/py.png"
 
 APPXMANIFEST_NS = {
     "": "http://schemas.microsoft.com/appx/manifest/foundation/windows10",
@@ -147,18 +154,22 @@
 
 SCCD_FILENAME = "PC/classicAppCompat.sccd"
 
+SPECIAL_LOOKUP = object()
+
 REGISTRY = {
     "HKCU\\Software\\Python\\PythonCore": {
         VER_DOT: {
             "DisplayName": APPX_DATA["DisplayName"],
             "SupportUrl": "https://www.python.org/",
-            "SysArchitecture": "64bit" if IS_X64 else "32bit",
+            "SysArchitecture": SPECIAL_LOOKUP,
             "SysVersion": VER_DOT,
             "Version": "{}.{}.{}".format(VER_MAJOR, VER_MINOR, VER_MICRO),
             "InstallPath": {
                 "": "[{AppVPackageRoot}]",
                 "ExecutablePath": "[{{AppVPackageRoot}}]\\python{}.exe".format(VER_DOT),
-                "WindowedExecutablePath": "[{{AppVPackageRoot}}]\\pythonw{}.exe".format(VER_DOT),
+                "WindowedExecutablePath": "[{{AppVPackageRoot}}]\\pythonw{}.exe".format(
+                    VER_DOT
+                ),
             },
             "Help": {
                 "Main Python Documentation": {
@@ -338,6 +349,16 @@
                 if len(fullkey.parts) > 1:
                     yield str(fullkey), None, None
             yield from _get_registry_entries(ns, fullkey, value)
+        elif value is SPECIAL_LOOKUP:
+            if key == "SysArchitecture":
+                return {
+                    "win32": "32bit",
+                    "amd64": "64bit",
+                    "arm32": "32bit",
+                    "arm64": "64bit",
+                }[ns.arch]
+            else:
+                raise ValueError(f"Key '{key}' unhandled for special lookup")
         elif len(r.parts) > 1:
             yield str(r), key, value
 
@@ -376,14 +397,18 @@
     NS = APPXMANIFEST_NS
     QN = ET.QName
 
+    data = dict(APPX_DATA)
+    for k, v in zip(APPX_PLATFORM_DATA["_keys"], APPX_PLATFORM_DATA[ns.arch]):
+        data[k] = v
+
     node = xml.find("m:Identity", NS)
     for k in node.keys():
-        value = APPX_DATA.get(k)
+        value = data.get(k)
         if value:
             node.set(k, value)
 
     for node in xml.find("m:Properties", NS):
-        value = APPX_DATA.get(node.tag.rpartition("}")[2])
+        value = data.get(node.tag.rpartition("}")[2])
         if value:
             node.text = value
 
@@ -405,7 +430,7 @@
         ["python", "python{}".format(VER_MAJOR), "python{}".format(VER_DOT)],
         PYTHON_VE_DATA,
         "console",
-        ("python.file", [".py"], '"%1"', 'Python File', PY_PNG),
+        ("python.file", [".py"], '"%1"', "Python File", PY_PNG),
     )
 
     add_application(
@@ -416,7 +441,7 @@
         ["pythonw", "pythonw{}".format(VER_MAJOR), "pythonw{}".format(VER_DOT)],
         PYTHONW_VE_DATA,
         "windows",
-        ("python.windowedfile", [".pyw"], '"%1"', 'Python File (no console)', PY_PNG),
+        ("python.windowedfile", [".pyw"], '"%1"', "Python File (no console)", PY_PNG),
     )
 
     if ns.include_pip and ns.include_launchers:
@@ -428,7 +453,7 @@
             ["pip", "pip{}".format(VER_MAJOR), "pip{}".format(VER_DOT)],
             PIP_VE_DATA,
             "console",
-            ("python.wheel", [".whl"], 'install "%1"', 'Python Wheel'),
+            ("python.wheel", [".whl"], 'install "%1"', "Python Wheel"),
         )
 
     if ns.include_idle and ns.include_launchers:
diff --git a/PC/layout/support/constants.py b/PC/layout/support/constants.py
index d76fa3b..a864763 100644
--- a/PC/layout/support/constants.py
+++ b/PC/layout/support/constants.py
@@ -5,15 +5,31 @@
 __author__ = "Steve Dower <steve.dower@python.org>"
 __version__ = "3.8"
 
+import os
+import re
 import struct
 import sys
 
-VER_MAJOR, VER_MINOR, VER_MICRO, VER_FIELD4 = struct.pack(">i", sys.hexversion)
+
+def _unpack_hexversion():
+    try:
+        hexversion = int(os.getenv("PYTHON_HEXVERSION"), 16)
+    except (TypeError, ValueError):
+        hexversion = sys.hexversion
+    return struct.pack(">i", sys.hexversion)
+
+
+def _get_suffix(field4):
+    name = {0xA0: "a", 0xB0: "b", 0xC0: "c"}.get(field4 & 0xF0, "")
+    if name:
+        serial = field4 & 0x0F
+        return f"{name}{serial}"
+    return ""
+
+
+VER_MAJOR, VER_MINOR, VER_MICRO, VER_FIELD4 = _unpack_hexversion()
+VER_SUFFIX = _get_suffix(VER_FIELD4)
 VER_FIELD3 = VER_MICRO << 8 | VER_FIELD4
-VER_NAME = {"alpha": "a", "beta": "b", "candidate": "rc"}.get(
-    sys.version_info.releaselevel, ""
-)
-VER_SERIAL = sys.version_info.serial if VER_NAME else ""
 VER_DOT = "{}.{}".format(VER_MAJOR, VER_MINOR)
 
 PYTHON_DLL_NAME = "python{}{}.dll".format(VER_MAJOR, VER_MINOR)
@@ -21,8 +37,6 @@
 PYTHON_ZIP_NAME = "python{}{}.zip".format(VER_MAJOR, VER_MINOR)
 PYTHON_PTH_NAME = "python{}{}._pth".format(VER_MAJOR, VER_MINOR)
 
-PYTHON_CHM_NAME = "python{}{}{}{}{}.chm".format(
-    VER_MAJOR, VER_MINOR, VER_MICRO, VER_NAME, VER_SERIAL
+PYTHON_CHM_NAME = "python{}{}{}{}.chm".format(
+    VER_MAJOR, VER_MINOR, VER_MICRO, VER_SUFFIX
 )
-
-IS_X64 = sys.maxsize > 2 ** 32
diff --git a/PC/layout/support/nuspec.py b/PC/layout/support/nuspec.py
index ba26ff3..b85095c 100644
--- a/PC/layout/support/nuspec.py
+++ b/PC/layout/support/nuspec.py
@@ -13,25 +13,21 @@
 NUSPEC_DATA = {
     "PYTHON_TAG": VER_DOT,
     "PYTHON_VERSION": os.getenv("PYTHON_NUSPEC_VERSION"),
-    "PYTHON_BITNESS": "64-bit" if IS_X64 else "32-bit",
-    "PACKAGENAME": os.getenv("PYTHON_NUSPEC_PACKAGENAME"),
-    "PACKAGETITLE": os.getenv("PYTHON_NUSPEC_PACKAGETITLE"),
     "FILELIST": r'    <file src="**\*" target="tools" />',
 }
 
+NUSPEC_PLATFORM_DATA = dict(
+    _keys=("PYTHON_BITNESS", "PACKAGENAME", "PACKAGETITLE"),
+    win32=("32-bit", "pythonx86", "Python (32-bit)"),
+    amd64=("64-bit", "python", "Python"),
+    arm32=("ARM", "pythonarm", "Python (ARM)"),
+    arm64=("ARM64", "pythonarm64", "Python (ARM64)"),
+)
+
 if not NUSPEC_DATA["PYTHON_VERSION"]:
-    if VER_NAME:
-        NUSPEC_DATA["PYTHON_VERSION"] = "{}.{}-{}{}".format(
-            VER_DOT, VER_MICRO, VER_NAME, VER_SERIAL
-        )
-    else:
-        NUSPEC_DATA["PYTHON_VERSION"] = "{}.{}".format(VER_DOT, VER_MICRO)
-
-if not NUSPEC_DATA["PACKAGETITLE"]:
-    NUSPEC_DATA["PACKAGETITLE"] = "Python" if IS_X64 else "Python (32-bit)"
-
-if not NUSPEC_DATA["PACKAGENAME"]:
-    NUSPEC_DATA["PACKAGENAME"] = "python" if IS_X64 else "pythonx86"
+    NUSPEC_DATA["PYTHON_VERSION"] = "{}.{}{}{}".format(
+        VER_DOT, VER_MICRO, "-" if VER_SUFFIX else "", VER_SUFFIX
+    )
 
 FILELIST_WITH_PROPS = r"""    <file src="**\*" exclude="python.props" target="tools" />
     <file src="python.props" target="build\native" />"""
@@ -56,11 +52,21 @@
 """
 
 
+def _get_nuspec_data_overrides(ns):
+    for k, v in zip(NUSPEC_PLATFORM_DATA["_keys"], NUSPEC_PLATFORM_DATA[ns.arch]):
+        ev = os.getenv("PYTHON_NUSPEC_" + k)
+        if ev:
+            yield k, ev
+        yield k, v
+
+
 def get_nuspec_layout(ns):
     if ns.include_all or ns.include_nuspec:
-        data = NUSPEC_DATA
+        data = dict(NUSPEC_DATA)
+        for k, v in _get_nuspec_data_overrides(ns):
+            if not data.get(k):
+                data[k] = v
         if ns.include_all or ns.include_props:
-            data = dict(data)
             data["FILELIST"] = FILELIST_WITH_PROPS
         nuspec = NUSPEC_TEMPLATE.format_map(data)
         yield "python.nuspec", ("python.nuspec", nuspec.encode("utf-8"))
diff --git a/PC/layout/support/props.py b/PC/layout/support/props.py
index 4d3b061..b1560b5 100644
--- a/PC/layout/support/props.py
+++ b/PC/layout/support/props.py
@@ -18,15 +18,9 @@
 }
 
 if not PROPS_DATA["PYTHON_VERSION"]:
-    if VER_NAME:
-        PROPS_DATA["PYTHON_VERSION"] = "{}.{}-{}{}".format(
-            VER_DOT, VER_MICRO, VER_NAME, VER_SERIAL
-        )
-    else:
-        PROPS_DATA["PYTHON_VERSION"] = "{}.{}".format(VER_DOT, VER_MICRO)
-
-if not PROPS_DATA["PYTHON_PLATFORM"]:
-    PROPS_DATA["PYTHON_PLATFORM"] = "x64" if IS_X64 else "Win32"
+    PROPS_DATA["PYTHON_VERSION"] = "{}.{}{}{}".format(
+        VER_DOT, VER_MICRO, "-" if VER_SUFFIX else "", VER_SUFFIX
+    )
 
 PROPS_DATA["PYTHON_TARGET"] = "_GetPythonRuntimeFilesDependsOn{}{}_{}".format(
     VER_MAJOR, VER_MINOR, PROPS_DATA["PYTHON_PLATFORM"]
@@ -94,5 +88,13 @@
 def get_props_layout(ns):
     if ns.include_all or ns.include_props:
         # TODO: Filter contents of props file according to included/excluded items
-        props = PROPS_TEMPLATE.format_map(PROPS_DATA)
+        d = dict(PROPS_DATA)
+        if not d.get("PYTHON_PLATFORM"):
+            d["PYTHON_PLATFORM"] = {
+                "win32": "Win32",
+                "amd64": "X64",
+                "arm32": "ARM",
+                "arm64": "ARM64",
+            }[ns.arch]
+        props = PROPS_TEMPLATE.format_map(d)
         yield "python.props", ("python.props", props.encode("utf-8"))
diff --git a/PCbuild/build.bat b/PCbuild/build.bat
index bce5993..623409c 100644
--- a/PCbuild/build.bat
+++ b/PCbuild/build.bat
@@ -57,7 +57,7 @@
 set target=Build
 set dir=%~dp0
 set parallel=/m
-set verbose=/nologo /v:m
+set verbose=/nologo /v:m /clp:summary
 set kill=
 set do_pgo=
 set pgo_job=-m test --pgo
diff --git a/PCbuild/find_msbuild.bat b/PCbuild/find_msbuild.bat
index a2810f0..bc9d00c 100644
--- a/PCbuild/find_msbuild.bat
+++ b/PCbuild/find_msbuild.bat
@@ -32,7 +32,7 @@
 @rem VS 2017 and later provide vswhere.exe, which can be used
 @if not exist "%ProgramFiles(x86)%\Microsoft Visual Studio\Installer\vswhere.exe" goto :skip_vswhere
 @set _Py_MSBuild_Root=
-@for /F "tokens=*" %%i in ('"%ProgramFiles(x86)%\Microsoft Visual Studio\Installer\vswhere.exe" -property installationPath -latest') DO @(set _Py_MSBuild_Root=%%i\MSBuild)
+@for /F "tokens=*" %%i in ('"%ProgramFiles(x86)%\Microsoft Visual Studio\Installer\vswhere.exe" -property installationPath -latest -prerelease') DO @(set _Py_MSBuild_Root=%%i\MSBuild)
 @if not defined _Py_MSBuild_Root goto :skip_vswhere
 @for %%j in (Current 15.0) DO @if exist "%_Py_MSBuild_Root%\%%j\Bin\msbuild.exe" (set MSBUILD="%_Py_MSBuild_Root%\%%j\Bin\msbuild.exe")
 @set _Py_MSBuild_Root=
diff --git a/PCbuild/pcbuild.proj b/PCbuild/pcbuild.proj
index 35f173f..22a9eed 100644
--- a/PCbuild/pcbuild.proj
+++ b/PCbuild/pcbuild.proj
@@ -60,7 +60,7 @@
     <!-- _ssl will build _socket as well, which may cause conflicts in parallel builds -->
     <ExtensionModules Include="_socket" Condition="!$(IncludeSSL) or !$(IncludeExternals)" />
     <ExternalModules Include="_ssl;_hashlib" Condition="$(IncludeSSL)" />
-    <ExternalModules Include="_tkinter" Condition="$(IncludeTkinter)" />
+    <ExternalModules Include="_tkinter" Condition="$(IncludeTkinter) and $(Platform) != 'ARM' and $(Platform) != 'ARM64'" />
     <ExtensionModules Include="@(ExternalModules->'%(Identity)')" Condition="$(IncludeExternals)" />
     <Projects Include="@(ExtensionModules->'%(Identity).vcxproj')" Condition="$(IncludeExtensions)" />
     <!-- Test modules -->
diff --git a/PCbuild/prepare_libffi.bat b/PCbuild/prepare_libffi.bat
index c65a5f7..f41ba83 100644
--- a/PCbuild/prepare_libffi.bat
+++ b/PCbuild/prepare_libffi.bat
@@ -93,7 +93,10 @@
 echo MSVCC        : %MSVCC%
 echo.
 
-if not exist Makefile.in (%SH% -lc "(cd $LIBFFI_SOURCE; ./autogen.sh;)")
+if not exist Makefile.in (
+    %SH% -lc "(cd $LIBFFI_SOURCE; ./autogen.sh;)"
+    if errorlevel 1 exit /B 1
+)
 
 if "%BUILD_X64%"=="1" call :BuildOne x64 x86_64-w64-cygwin x86_64-w64-cygwin
 if "%BUILD_X86%"=="1" call :BuildOne x86 i686-pc-cygwin i686-pc-cygwin
@@ -158,11 +161,13 @@
 echo Configure the build to generate fficonfig.h and ffi.h
 echo ================================================================
 %SH% -lc "(cd $OLDPWD; ./configure CC='%MSVCC% %ASSEMBLER% %BUILD_PDB%' CXX='%MSVCC% %ASSEMBLER% %BUILD_PDB%' LD='link' CPP='cl -nologo -EP' CXXCPP='cl -nologo -EP' CPPFLAGS='-DFFI_BUILDING_DLL' %BUILD_NOOPT% NM='dumpbin -symbols' STRIP=':' --build=$BUILD --host=$HOST;)"
+if errorlevel 1 exit /B %ERRORLEVEL%
 
 echo ================================================================
 echo Building libffi
 echo ================================================================
 %SH% -lc "(cd $OLDPWD; export PATH=/usr/bin:$PATH; cp src/%SRC_ARCHITECTURE%/ffitarget.h include; make; find .;)"
+if errorlevel 1 exit /B %ERRORLEVEL%
 
 REM Tests are not needed to produce artifacts
 if "%LIBFFI_TEST%" EQU "1" (
diff --git a/PCbuild/python_uwp.vcxproj b/PCbuild/python_uwp.vcxproj
index 14e138c..5ff120a 100644
--- a/PCbuild/python_uwp.vcxproj
+++ b/PCbuild/python_uwp.vcxproj
@@ -1,6 +1,14 @@
 ﻿<?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|ARM">
+      <Configuration>Debug</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|ARM64">
+      <Configuration>Debug</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="Debug|Win32">
       <Configuration>Debug</Configuration>
       <Platform>Win32</Platform>
@@ -9,6 +17,14 @@
       <Configuration>Debug</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|ARM">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|ARM64">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="PGInstrument|Win32">
       <Configuration>PGInstrument</Configuration>
       <Platform>Win32</Platform>
@@ -17,6 +33,14 @@
       <Configuration>PGInstrument</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|ARM">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|ARM64">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="PGUpdate|Win32">
       <Configuration>PGUpdate</Configuration>
       <Platform>Win32</Platform>
@@ -25,6 +49,14 @@
       <Configuration>PGUpdate</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM">
+      <Configuration>Release</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM64">
+      <Configuration>Release</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="Release|Win32">
       <Configuration>Release</Configuration>
       <Platform>Win32</Platform>
diff --git a/PCbuild/pythonw_uwp.vcxproj b/PCbuild/pythonw_uwp.vcxproj
index e2c0171..828d0d1 100644
--- a/PCbuild/pythonw_uwp.vcxproj
+++ b/PCbuild/pythonw_uwp.vcxproj
@@ -1,6 +1,14 @@
 ﻿<?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|ARM">
+      <Configuration>Debug</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|ARM64">
+      <Configuration>Debug</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="Debug|Win32">
       <Configuration>Debug</Configuration>
       <Platform>Win32</Platform>
@@ -9,6 +17,14 @@
       <Configuration>Debug</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|ARM">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|ARM64">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="PGInstrument|Win32">
       <Configuration>PGInstrument</Configuration>
       <Platform>Win32</Platform>
@@ -17,6 +33,14 @@
       <Configuration>PGInstrument</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|ARM">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|ARM64">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="PGUpdate|Win32">
       <Configuration>PGUpdate</Configuration>
       <Platform>Win32</Platform>
@@ -25,6 +49,14 @@
       <Configuration>PGUpdate</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM">
+      <Configuration>Release</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM64">
+      <Configuration>Release</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="Release|Win32">
       <Configuration>Release</Configuration>
       <Platform>Win32</Platform>