diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 5d464414c6..826ee22620 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -68,3 +68,43 @@ jobs:
     - run: git config user.email ci@sel4.systems
     - run: git commit -m "auto-deployed"
     - run: git push
+
+  # Push platforms.json to the website repo if changed
+  platforms-push:
+    if: ${{ github.repository_owner == 'seL4' &&
+            (github.event_name == 'push' || github.event_name == 'schedule' ||
+            github.event_name == 'workflow_dispatch') }}
+    needs: build
+    name: 'Update platforms.json on website'
+    runs-on: ubuntu-24.04
+    steps:
+    # fetch only _data/ and top-level files, not the full repo and no large files
+    - name: Check out website repo
+      uses: actions/checkout@v6
+      with:
+        repository: seL4/website
+        path: website
+        token: ${{ secrets.PRIV_REPO_TOKEN }}
+        fetch-depth: 1
+        filter: blob:none
+        sparse-checkout: _data
+    - uses: actions/download-artifact@v8
+      with:
+        name: site
+    - name: Unpack site
+      run: tar -xvf site.tar _site/Hardware/platforms.json
+    - name: Validate json
+      run: jq empty _site/Hardware/platforms.json
+    - name: Push to website
+      run: |
+        cp _site/Hardware/platforms.json website/_data/platforms.json
+        cd website
+        git add _data/platforms.json
+        if git diff --cached --quiet; then
+          echo "platforms.json unchanged"
+          exit 0
+        fi
+        git config user.name "seL4 CI"
+        git config user.email "ci@sel4.systems"
+        git commit -s -m "CI: update platforms from docsite"
+        git push origin HEAD:master
diff --git a/Hardware/platforms.json b/Hardware/platforms.json
index 949804bf5a..5121c5c13c 100644
--- a/Hardware/platforms.json
+++ b/Hardware/platforms.json
@@ -3,34 +3,10 @@ layout: null
 SPDX-License-Identifier: CC-BY-SA-4.0
 SPDX-FileCopyrightText: 2025 seL4 International
 ---
-
+{%- assign arm = site.pages | where_exp: "p", "p.arm_hardware and p.Maintained" | sort: "platform" | map: "platform" %}
+{%- assign riscv = site.pages | where_exp: "p", "p.riscv_hardware and p.Maintained" | sort: "platform" | map: "platform" %}
 [
-  [
-    "Arm",
-    [
-{%- assign sorted = site.pages | sort: 'platform' %}
-{%- for page in sorted %}
-{%-   if page.arm_hardware and page.Maintained %}
-      "{{ page.platform }}"{% unless forloop.last %},{% endunless %}
-{%-   endif %}
-{%- endfor %}
-    ]
-  ],
-  [
-    "RISC-V",
-    [
-{%- assign sorted = site.pages | sort: 'platform' %}
-{%- for page in sorted %}
-{%-   if page.riscv_hardware and page.Maintained %}
-      "{{ page.platform }}"{% unless forloop.last %},{% endunless %}
-{%-   endif %}
-{%- endfor %}
-    ]
-  ],
-  [
-    "Intel",
-    [
-      "32 and 64 bit PC-99 machines"
-    ]
-  ]
+  ["Arm", {{ arm | jsonify }}],
+  ["RISC-V", {{ riscv | jsonify }}],
+  ["Intel", ["32 and 64 bit PC-99 machines"]]
 ]