diff --git a/index.html b/index.html
index 4071ba58..71f39eb7 100644
--- a/index.html
+++ b/index.html
@@ -15,6 +15,7 @@
     <link rel="icon" type="image/png" href="images/favicon-16x16.png" sizes="16x16" />
     <link rel="canonical" href="https://azgaar.github.io/Fantasy-Map-Generator/" />
 
+    <!-- inline css for loading screen -->
     <style type="text/css">
       body {
         margin: 0;
@@ -70,7 +71,7 @@
         font-size: 7em;
         margin: -12px 0 -6px 0;
       }
-      #version {
+      #versionText {
         text-align: right;
         font-size: 2em;
         margin-right: 3%;
@@ -274,7 +275,7 @@
     <div id="loading">
       <div id="titleName"><t data-t="titleName">Azgaar's</t></div>
       <div id="title"><t data-t="title">Fantasy Map Generator</t></div>
-      <div id="version"><t data-t="version">v. </t>1.8</div>
+      <div id="versionText"><t data-t="version">v. </t><span id="version"></span></div>
       <p id="loading-text"><t data-t="loading">LOADING</t><span>.</span><span>.</span><span>.</span></p>
     </div>
 
@@ -6238,8 +6239,10 @@
         </g>
       </defs>
     </svg>
-
+    
     <script src="libs/jquery-3.1.1.min.js"></script>
+    <script src="libs/jquery-ui.min.js"></script>
+    <script src="versioning.js"></script>
     <script src="libs/d3.min.js"></script>
     <script src="libs/priority-queue.min.js"></script>
     <script src="libs/delaunator.min.js"></script>
@@ -6272,13 +6275,11 @@
     <script src="modules/submap.js"></script>
     <script src="libs/polylabel.min.js"></script>
     <script src="libs/lineclip.min.js"></script>
-    <script src="libs/jquery-ui.min.js"></script>
     <script src="libs/alea.min.js"></script>
     <script src="modules/fonts.js"></script>
     <script src="modules/ui/layers.js"></script>
     <script src="modules/ui/measurers.js"></script>
     <script src="modules/ui/stylePresets.js"></script>
-    <!-- <script src="libs/umami.js"></script> -->
 
     <script src="modules/ui/general.js"></script>
     <script src="modules/ui/options.js"></script>
diff --git a/main.js b/main.js
index 39a70d29..e196c703 100644
--- a/main.js
+++ b/main.js
@@ -2,10 +2,7 @@
 // https://github.com/Azgaar/Fantasy-Map-Generator
 
 "use strict";
-const version = "1.8"; // generator version
-document.title += " v" + version;
-
-// switches to disable/enable logging features
+// set debug options
 const PRODUCTION = location.hostname && location.hostname !== "localhost" && location.hostname !== "127.0.0.1";
 const DEBUG = localStorage.getItem("debug");
 const INFO = DEBUG || !PRODUCTION;
@@ -13,10 +10,13 @@ const TIME = DEBUG || !PRODUCTION;
 const WARN = true;
 const ERROR = true;
 
-// if map version is not stored, clear localStorage and show a message
-if (rn(localStorage.getItem("version"), 1) !== rn(version, 1)) {
-  localStorage.clear();
-  setTimeout(showWelcomeMessage, 8000);
+// register service worker responsible for caching
+if (PRODUCTION && "serviceWorker" in navigator) {
+  window.addEventListener("load", () => {
+    navigator.serviceWorker.register("/sw.js").catch(err => {
+      console.error("ServiceWorker registration failed: ", err);
+    });
+  });
 }
 
 // append svg layers (in default order)
@@ -449,44 +449,6 @@ function applyDefaultBiomesSystem() {
   return {i: d3.range(0, name.length), name, color, biomesMartix, habitability, iconsDensity, icons, cost};
 }
 
-function showWelcomeMessage() {
-  const changelog = link("https://github.com/Azgaar/Fantasy-Map-Generator/wiki/Changelog", "previous versions");
-  const reddit = link("https://www.reddit.com/r/FantasyMapGenerator", "Reddit community");
-  const discord = link("https://discordapp.com/invite/X7E84HU", "Discord server");
-  const patreon = link("https://www.patreon.com/azgaar", "Patreon");
-
-  alertMessage.innerHTML = /* html */ `The Fantasy Map Generator is updated up to version <strong>${version}</strong>. This version is compatible with ${changelog},
-    loaded <i>.map</i> files will be auto-updated.
-    <ul>
-      <strong>Latest changes:</strong>
-      <li>Submap tool by Goteguru</li>
-      <li>Resample tool by Goteguru</li>
-      <li>Pre-defined heightmaps</li>
-      <li>Advanced notes editor</li>
-      <li>Zones editor: filter by type</li>
-      <li>Color picker: new hatchings</li>
-      <li>New style presets: Cyberpunk and Atlas</li>
-      <li>Burg temperature graph</li>
-      <li>4 new textures</li>
-    </ul>
-
-    <p>Join our ${discord} and ${reddit} to ask questions, share maps, discuss the Generator and Worlbuilding, report bugs and propose new features.</p>
-    <span><i>Thanks for all supporters on ${patreon}!</i></span>`;
-
-  $("#alert").dialog({
-    resizable: false,
-    title: "Fantasy Map Generator update",
-    width: "28em",
-    buttons: {
-      OK: function () {
-        $(this).dialog("close");
-      }
-    },
-    position: {my: "center center-4em", at: "center", of: "svg"},
-    close: () => localStorage.setItem("version", version)
-  });
-}
-
 function doWorkOnZoom(isScaleChanged, isPositionChanged) {
   viewbox.attr("transform", `translate(${viewX} ${viewY}) scale(${scale})`);
 
diff --git a/sw.js b/sw.js
new file mode 100644
index 00000000..8c88393e
--- /dev/null
+++ b/sw.js
@@ -0,0 +1,68 @@
+importScripts("https://storage.googleapis.com/workbox-cdn/releases/6.2.0/workbox-sw.js");
+
+const {Route, registerRoute} = workbox.routing;
+const {CacheFirst} = workbox.strategies;
+const {CacheableResponsePlugin} = workbox.cacheableResponse;
+const {ExpirationPlugin} = workbox.expiration;
+
+const DAY = 24 * 60 * 60;
+
+const getPolitics = ({entries, days}) => {
+  return [new CacheableResponsePlugin({statuses: [200]}), new ExpirationPlugin({maxEntries: entries, maxAgeSeconds: days * DAY})];
+};
+
+registerRoute(
+  ({request, url}) => request.destination === "script" && !url.pathname.endsWith("min.js") && !url.pathname.includes("versioning.js"),
+  new CacheFirst({
+    cacheName: "fmg-scripts",
+    plugins: getPolitics({entries: 100, days: 30})
+  })
+);
+
+registerRoute(
+  ({request}) => request.destination === "style",
+  new CacheFirst({
+    cacheName: "fmg-stylesheets",
+    plugins: getPolitics({entries: 100, days: 30})
+  })
+);
+
+registerRoute(
+  ({request, url}) => request.destination === "script" && url.pathname.endsWith("min.js"),
+  new CacheFirst({
+    cacheName: "fmg-libs",
+    plugins: getPolitics({entries: 100, days: 30})
+  })
+);
+
+registerRoute(
+  new RegExp(".json$"),
+  new CacheFirst({
+    cacheName: "fmg-json",
+    plugins: getPolitics({entries: 100, days: 30})
+  })
+);
+
+registerRoute(
+  ({request}) => request.destination === "image",
+  new CacheFirst({
+    cacheName: "fmg-images",
+    plugins: getPolitics({entries: 1000, days: 30})
+  })
+);
+
+registerRoute(
+  new RegExp(".svg$"),
+  new CacheFirst({
+    cacheName: "fmg-charges",
+    plugins: getPolitics({entries: 1000, days: 30})
+  })
+);
+
+registerRoute(
+  ({request}) => request.destination === "font",
+  new CacheFirst({
+    cacheName: "fmg-fonts",
+    plugins: getPolitics({entries: 200, days: 30})
+  })
+);
diff --git a/versioning.js b/versioning.js
new file mode 100644
index 00000000..94e9da46
--- /dev/null
+++ b/versioning.js
@@ -0,0 +1,73 @@
+"use strict";
+// version and caching control
+
+const version = "1.81"; // generator version, update each time
+
+{
+  document.title += " v" + version;
+  const loadingScreenVersion = document.getElementById("version");
+  if (loadingScreenVersion) loadingScreenVersion.innerHTML = version;
+
+  const majorVersion = Math.round(version * 10) / 10;
+  const storedVersion = +localStorage.getItem("version") || 0;
+
+  const showUpdate = storedVersion < majorVersion;
+  if (showUpdate) setTimeout(showUpdateWindow, 5000);
+
+  function showUpdateWindow() {
+    const changelog = "https://github.com/Azgaar/Fantasy-Map-Generator/wiki/Changelog";
+    const reddit = "https://www.reddit.com/r/FantasyMapGenerator";
+    const discord = "https://discordapp.com/invite/X7E84HU";
+    const patreon = "https://www.patreon.com/azgaar";
+
+    alertMessage.innerHTML = /* html */ `The Fantasy Map Generator is updated up to version <strong>${version}</strong>. This version is compatible with <a href="${changelog}" target="_blank">previous versions</a>, loaded <i>.map</i> files will be auto-updated.
+      ${storedVersion ? "<span>Reload the page to fetch fresh code.</span>" : ""}
+
+      <ul>
+        <strong>Latest changes:</strong>
+        <li>Caching for faster startup</li>
+        <li>Submap tool by Goteguru</li>
+        <li>Resample tool by Goteguru</li>
+        <li>Pre-defined heightmaps</li>
+        <li>Advanced notes editor</li>
+        <li>Zones editor: filter by type</li>
+        <li>Color picker: new hatchings</li>
+        <li>New style presets: Cyberpunk and Atlas</li>
+        <li>Burg temperature graph</li>
+        <li>4 new textures</li>
+      </ul>
+
+      <p>Join our <a href="${discord}" target="_blank">Discord server</a> and <a href="${reddit}" target="_blank">Reddit community</a> to ask questions, share maps, discuss the Generator and Worlbuilding, report bugs and propose new features.</p>
+      <span><i>Thanks for all supporters on <a href="${patreon}" target="_blank">Patreon</a>!</i></span>`;
+
+    const buttons = {
+      Ok: function () {
+        $(this).dialog("close");
+        if (storedVersion) clearStoredData();
+      }
+    };
+
+    if (storedVersion) {
+      buttons.Reload = () => {
+        clearStoredData();
+        location.reload();
+      };
+    }
+
+    $("#alert").dialog({
+      resizable: false,
+      title: "Fantasy Map Generator update",
+      width: "28em",
+      position: {my: "center center-4em", at: "center", of: "svg"},
+      buttons
+    });
+  }
+
+  async function clearStoredData() {
+    localStorage.clear();
+    localStorage.setItem("version", version);
+
+    const cacheNames = await caches.keys();
+    Promise.all(cacheNames.map(cacheName => caches.delete(cacheName)));
+  }
+}