diff --git a/.github/workflows/macOS.yml b/.github/workflows/macOS.yml
index 2d9db6f..799ddec 100644
--- a/.github/workflows/macOS.yml
+++ b/.github/workflows/macOS.yml
@@ -55,10 +55,8 @@ jobs:
       - name:  assemble bundle
         run: |
           bash build-mac-app.sh
-          mv macos/snappy/SnapPy.app .
-          tar cfz Snappy_app.tgz SnapPy.app
 
       - uses: actions/upload-artifact@v3
         with:
-          name: SnapPy_app.tgz
-          path: ./SnapPy_app.tgz
+          name: SnapPy.dmg
+          path: ./macOS/dmg-maker/SnapPy.dmg
diff --git a/build-mac-app.sh b/build-mac-app.sh
index a24516b..bda112b 100644
--- a/build-mac-app.sh
+++ b/build-mac-app.sh
@@ -3,3 +3,8 @@ cd macOS
 rm -rf snappy/SnapPy.app
 . bin/make-bundle.sh
 . bin/sign-bundle.sh
+rm -rf dist
+mkdir dist
+mv snappy/SnapPy.app dist
+. bin/notarize.sh
+
diff --git a/macOS/bin/notarize.sh b/macOS/bin/notarize.sh
new file mode 100644
index 0000000..0cf0660
--- /dev/null
+++ b/macOS/bin/notarize.sh
@@ -0,0 +1,18 @@
+#!/bin/bash
+source Ids.sh
+set -e
+cd dmg-maker
+APP="../dist/SnapPy.app"
+DMG="SnapPy.dmg"
+OPTIONS="--wait --no-progress --apple-id $USERNAME \
+--team-id $IDENTITY --password $PASSWORD --wait"
+python3 dmg-maker.py
+echo "Notarizing app ..."
+xcrun notarytool submit $DMG $OPTIONS
+xcrun stapler staple $APP
+python3 dmg-maker.py
+echo "Signing disk image ..."
+codesign -s $IDENTITY --timestamp --options runtime --force $DMG
+echo "Notarizing disk image ..."
+xcrun notarytool submit $DMG $OPTIONS
+xcrun stapler staple $DMG
diff --git a/macOS/bin/sign-bundle.sh b/macOS/bin/sign-bundle.sh
index bc81fea..c30aa4d 100644
--- a/macOS/bin/sign-bundle.sh
+++ b/macOS/bin/sign-bundle.sh
@@ -4,7 +4,7 @@ set -e
 APP=SnapPy.app
 WORK_DIR=snappy
 
-echo Signing SnapPy.app
+echo "Signing $APP ..."
 FRAMEWORKS=$APP/Contents/Frameworks
 MACOS=$APP/Contents/MacOS
 pushd $WORK_DIR
@@ -24,6 +24,8 @@ done
 
 $SIGN $APP
 # Of course spctl will fail, since the app is not notarized.
-# But we want to see what it says.
+# But we want to see what it says anyway.
+echo "Verifying with spctl - should be rejected as unnotarized ..."
 spctl --verbose --assess SnapPy.app || true
 popd
+
diff --git a/macOS/dmg-maker/background.png b/macOS/dmg-maker/background.png
new file mode 100644
index 0000000..25b31a8
Binary files /dev/null and b/macOS/dmg-maker/background.png differ
diff --git a/macOS/dmg-maker/dmg-maker.py b/macOS/dmg-maker/dmg-maker.py
new file mode 100755
index 0000000..e19ec89
--- /dev/null
+++ b/macOS/dmg-maker/dmg-maker.py
@@ -0,0 +1,68 @@
+#! /usr/bin/env python3
+"""
+Creates a nice disk image, with background and /Applications symlink
+for the app.
+
+One issue here is that Snow Leopard uses a different (undocumented, of
+course) format for the .DS_Store files than earlier versions, which makes
+disk images created on it not work correctly on those systems.   Thus this "solution" uses a .DS_Store file created on Leopard as follows:
+
+(1) Use Disk Utility to create a r/w DMG large enough to store everything and open it.
+
+(2) Copy over the application and add a symlink to /Applications.
+
+(3) Create a subdirectory ".background" containing the file "background.png".
+
+(4) Open the disk image in the Finder and do View->Hide Tool Bar and then View->Show View Options.  To add the background picture inside the hidden directory, use cmd-shift-g in the file dialog.  Adjust everything to suit, close window and open it.   Then copy the .DS_Store file to dotDS_store.  
+
+"""
+import os
+import re
+import shutil
+from subprocess import check_call
+from math import ceil
+
+name = "SnapPy"
+dist_dir = "../dist"
+print('dmg name is %s' % name)
+
+def main():
+    # Make sure the dmg isn't currently mounted, or this won't work.  
+    mount_name = "/Volumes/" + name
+    while os.path.exists(mount_name):
+        print("Trying to eject " + mount_name)
+        subprocess.check_call("hdiutil detach " + mount_name)
+    # Remove old dmg if there is one
+    while os.path.exists(name + ".dmg"):
+        os.remove(name + ".dmg")
+    while os.path.exists(name + "-tmp.dmg"):
+        os.remove(name + "-tmp.dmg")
+    # Add symlink to /Applications if not there:
+    if not os.path.exists(dist_dir + "/Applications"):
+        os.symlink("/Applications/", dist_dir + "/Applications")
+
+    # copy over the background and .DS_Store file
+    background = os.path.join(dist_dir, '.background')
+    shutil.rmtree(background, ignore_errors=True)
+    os.mkdir(background)
+    shutil.copy('background.png', background)
+    shutil.copy('dotDS_Store', os.path.join(dist_dir, '.DS_Store'))
+                    
+    # figure out the needed size:
+    raw_size = os.popen("du -sh " + dist_dir).read()
+    size, units = re.search("([0-9.]+)([KMG])", raw_size).groups()
+    new_size = "%d" % ceil(1.2 * float(size)) + units
+    # Run the main script:
+    check_call(['hdiutil', 'makehybrid', '-hfs',
+                '-hfs-volume-name', 'SnapPy',
+                '-hfs-openfolder', dist_dir,
+                '-o', 'SnapPy-tmp.dmg',
+                dist_dir] )
+    check_call(['hdiutil', 'convert', '-format', 'UDZO',
+                'SnapPy-tmp.dmg', '-o', '%s.dmg'%name])
+    os.remove("SnapPy-tmp.dmg")
+    # Delete symlink to /Applications or egg_info will be glacial on newer setuptools.
+    os.remove(dist_dir + "/Applications")
+              
+if __name__ == "__main__":
+    main()
diff --git a/macOS/dmg-maker/dotDS_Store b/macOS/dmg-maker/dotDS_Store
new file mode 100644
index 0000000..c2018c9
Binary files /dev/null and b/macOS/dmg-maker/dotDS_Store differ