diff --git a/index.html b/index.html
index e812452..fb1ae60 100644
--- a/index.html
+++ b/index.html
@@ -13,6 +13,7 @@
       <div class="ol-unselectable ol-control close" style="pointer-events: auto;">
         <button onclick="document.body.classList.toggle('nav-open')">&lsaquo;</button>
       </div>
+      <div id="source"></div>
     </aside>
     <div id="map"></div>
     <div id="popup" class="ol-popup">
diff --git a/main.js b/main.js
index 73fc3f4..d768292 100644
--- a/main.js
+++ b/main.js
@@ -155,3 +155,8 @@ map.on('click', function (evt) {
 new ResizeObserver(() => map.updateSize()).observe(document.getElementById("map"));
 
 window.map = map;
+
+document.getElementById('source').innerHTML = `<a href="https://git.chandlerswift.com/chandlerswift/maps.chandlerswift.com/commit/${import.meta.env.VITE_GIT_COMMIT_HASH}">Source code</a>
+<!--
+${import.meta.env.VITE_FILE_DATES}
+-->`;
diff --git a/style.css b/style.css
index a0ddfed..67c0768 100644
--- a/style.css
+++ b/style.css
@@ -25,12 +25,20 @@ aside {
   transition: 0.25s;
   max-height: 100vh;
   overflow-y: auto;
+  display: flex;
+  flex-direction: column;
 }
 
 aside > div {
   padding: 0 0.5em;
 }
 
+#source {
+  order: 1;
+  margin: auto;
+  padding: 0.5em;
+}
+
 .nav-open aside {
   margin-left: 0;
 }
diff --git a/vite.config.js b/vite.config.js
index b7aa047..f7e7419 100644
--- a/vite.config.js
+++ b/vite.config.js
@@ -1,6 +1,18 @@
-export default {
-  build: {
-    sourcemap: true,
-    target: 'es2022',
+var childProcess = require('child_process');
+
+export default () => {
+  // https://stackoverflow.com/a/71162041/3814663
+  const commitDate = childProcess.execSync('git log -1 --format=%cI').toString().trimEnd();
+  const commitHash = childProcess.execSync('git rev-parse HEAD').toString().trimEnd();
+  const fileDates = childProcess.execSync(`find . -iname '*.geojson' -not -path './dist/*' | xargs ls -lh`).toString().trimEnd();
+  process.env.VITE_GIT_COMMIT_DATE = commitDate;
+  process.env.VITE_GIT_COMMIT_HASH = commitHash;
+  process.env.VITE_FILE_DATES = fileDates;
+
+  return {
+    build: {
+      sourcemap: true,
+      target: 'es2022',
+    }
   }
 }