diff --git a/docs/nix-flake-updates.md b/docs/nix-flake-updates.md
new file mode 100644
index 0000000..eef1613
--- /dev/null
+++ b/docs/nix-flake-updates.md
@@ -0,0 +1,43 @@
+Use these commands to show the diff between versions for planning updates:
+
+```
+OLD_CLOSURE=$(nix build --print-out-paths .#nixosConfigurations.nachtigall.config.system.build.toplevel)
+/nix/store/c6wqp1vzvyr3bq2igd8p460613ddwrmj-nixos-system-nachtigall-23.11.20231201.5de0b32
+```
+
+```
+nix flake update
+...
+```
+
+```
+NEW_CLOSURE=$(nix build --print-out-paths .#nixosConfigurations.nachtigall.config.system.build.toplevel)
+/nix/store/xynyf943d2nw1wgawhzxh13xkkf1whb0-nixos-system-nachtigall-23.11.20231210.781e2a9
+```
+
+```
+nix store diff-closures $OLD_CLOSURE $NEW_CLOSURE
+cpupower: 6.1.64 → 6.1.66
+element-web: 1.11.47 → 1.11.51, +5325.9 KiB
+element-web-wrapped: 1.11.47 → 1.11.51
+initrd-linux: 6.1.64 → 6.1.66
+keycloak: 22.0.5 → 23.0.0, +15201.4 KiB
+linux: 6.1.64, 6.1.64-modules → 6.1.66, 6.1.66-modules, +8.3 KiB
+mastodon: 4.2.1 → 4.2.3, +16.3 KiB
+mastodon-gems: 4.2.1 → 4.2.3, +14.4 KiB
+mastodon-modules: 4.2.1 → 4.2.3
+nix: +18.8 KiB
+nixos-manual: +73.6 KiB
+nixos-system-nachtigall: 23.11.20231201.5de0b32 → 23.11.20231210.781e2a9
+opensearch: 2.11.0 → 2.11.1, +560.5 KiB
+owncast: 0.1.1 → 0.1.2, +798.9 KiB
+ruby3.2.2-bcp47_spec: ∅ → 0.2.1, +13.6 KiB
+ruby3.2.2-json-canonicalization: 0.3.2 → 1.0.0
+ruby3.2.2-json-ld: 3.2.5 → 3.3.1
+ruby3.2.2-rdf: 3.2.11 → 3.3.1
+samba: +12.5 KiB
+source: +3888.1 KiB
+wrapped-ruby-mastodon-gems: 4.2.1 → 4.2.3
+zfs-kernel: 2.2.1-6.1.64 → 2.2.2-6.1.66
+zfs-user: 2.2.1 → 2.2.2
+```