diff --git a/src-ui/css/ui.css b/src-ui/css/ui.css
index 97c4ac8f0..d433b5cd7 100644
--- a/src-ui/css/ui.css
+++ b/src-ui/css/ui.css
@@ -614,6 +614,19 @@ form#fileform2 {
   content: "+";
 }
 
+div#saveicon {
+  float: right;
+  position: relative;
+  height: 100%;
+  display: flex;
+  align-items: center;
+  margin-right: 2px;
+  margin-top: 1px;
+}
+.hide {
+  visibility: hidden;
+}
+
 div#timertext {
   display: inline-block;
   padding: 2pt 0;
diff --git a/src-ui/js/list.js b/src-ui/js/list.js
index ea26a397d..b179a28c5 100644
--- a/src-ui/js/list.js
+++ b/src-ui/js/list.js
@@ -103,7 +103,7 @@
 				localStorage.getItem("pzprv3_config:ui") || "{}"
 			);
 			setting.listsort = typename;
-			localStorage.setItem("pzprv3_config:ui", JSON.stringify(setting));
+			pzpr.util.store("pzprv3_config:ui", JSON.stringify(setting));
 			self.apply_sort();
 		},
 
diff --git a/src-ui/js/ui/Boot.js b/src-ui/js/ui/Boot.js
index a0526f397..0749231e5 100644
--- a/src-ui/js/ui/Boot.js
+++ b/src-ui/js/ui/Boot.js
@@ -13,18 +13,42 @@
 	// ★boot() window.onload直後の処理
 	//---------------------------------------------------------------------------
 	pzpr.on("load", function boot() {
-		if (importData()) {
-			startPuzzle();
+		var pzl;
+		var storedGame = null;
+
+		if (pzpr.env.localStorageAvailable) {
+			// If localStorage is available and autosave is enabled:
+			// Get URL search hash and check localStorage to see if a board state is saved
+
+			// ui.menuconfig is not yet populated, so need to manually check
+			var json_menu = localStorage.getItem("pzprv3_config:ui");
+			if (json_menu && JSON.parse(json_menu)["autosave"]) {
+				var key = "pzpr_" + getPuzzleString();
+				storedGame = localStorage.getItem(key);
+			}
+		}
+
+		if (storedGame) {
+			var valObject = JSON.parse(storedGame);
+			pzl = importData(valObject.pzl);
 		} else {
+			pzl = importData();
+		}
+		if (!pzl) {
 			setTimeout(boot, 0);
 		}
+		startPuzzle();
 	});
 
-	function importData() {
+	function importData(string) {
 		if (!onload_pzl) {
 			/* 1) 盤面複製・index.htmlからのファイル入力/Database入力か */
 			/* 2) URL(?以降)をチェック */
-			onload_pzl = importURL();
+			if (!string) {
+				onload_pzl = importURL();
+			} else {
+				onload_pzl = importFromString(string);
+			}
 
 			/* 指定されたパズルがない場合はさようなら～ */
 			if (!onload_pzl || !onload_pzl.pid) {
@@ -90,26 +114,75 @@
 	//---------------------------------------------------------------------------
 	function importURL() {
 		/* index.htmlからURLが入力されていない場合は現在のURLの?以降をとってくる */
+		var puzString = getPuzzleString();
+		return importFromString(puzString);
+	}
+	//Splitting functionality from above for flexibility.
+
+	//Return the string associated with the puzzle
+	function getPuzzleString() {
 		var search = location.search;
 		if (!search) {
 			return null;
 		}
-
-		/* 一旦先頭の?記号を取り除く */
 		if (search.charAt(0) === "?") {
-			search = search.substr(1);
+			search = search.slice(1);
 		}
 
 		while (search.match(/^(\w+)\=(\w+)\&(.*)/)) {
 			onload_option[RegExp.$1] = RegExp.$2;
 			search = RegExp.$3;
 		}
+		return search;
+	}
+	//Import from a puzzle string. This can come from the URL or from localStorage
+	function importFromString(string) {
+		if (!string) {
+			return null;
+		}
 
-		onload_pzv = search;
-		var pzl = pzpr.parser.parseURL(search);
+		onload_pzv = string;
+		var pzl = pzpr.parser.parseURL(string);
 		var startmode = pzl.mode || (!pzl.body ? "editor" : "player");
 		onload_option.type = onload_option.type || startmode;
 
 		return pzl;
 	}
+
+	//---------------------------------------------------------------------------
+	// Functionality to support browser caching
+	//---------------------------------------------------------------------------
+
+	//Save board state. Creates an entry in localStorage whose key is a 'pzpr_' identifier plus the current board state puzzle string.
+	//Board state puzzle string is the same thing you get from duplicating the board state
+	//Auto-exits if the correct setting is not set, so safe to call from anywhere without checking
+	function saveBoardState() {
+		if (!ui.menuconfig.get("autosave")) {
+			return;
+		}
+		var key = "pzpr_" + getPuzzleString();
+		var url = ui.puzzle.getURL(
+			pzpr.parser.URL_PZPRFILE,
+			ui.puzzle.playeronly ? "player" : "editor"
+		);
+		//Strip url to the last option. This is the "puzzle string" we want
+		url = url.substring(url.indexOf("?") + 1); //Skip to the search parameters part of the url
+		while (url.match(/^(\w+)\=(\w+)\&(.*)/)) {
+			url = RegExp.$3;
+		}
+		//Add a time signifier so that we can sort and delete oldest if setting fails
+		var valObject = {
+			t: Date.now(),
+			pzl: url
+			// bufferToForceStorageLimitErrors: "0".repeat(1700000) //Include for testing to force out-of-storage errors
+		};
+		pzpr.util.store(key, JSON.stringify(valObject));
+	}
+
+	//Events that trigger a board state save
+	document.addEventListener("visibilitychange", function() {
+		if (document.visibilityState === "hidden") {
+			saveBoardState();
+		}
+	});
 })();
diff --git a/src-ui/js/ui/MenuConfig.js b/src-ui/js/ui/MenuConfig.js
index 44040e279..863d7b77e 100644
--- a/src-ui/js/ui/MenuConfig.js
+++ b/src-ui/js/ui/MenuConfig.js
@@ -50,6 +50,11 @@
 				volatile: true
 			}); /* マウスの左右ボタンを反転する設定 */
 
+			//Autosave feature. Not on by default, but persists once enabled
+			this.add("autosave", false, {
+				volatile: false
+			});
+
 			this.add("language", pzpr.lang, { option: ["en", "ja"] }); /* 言語設定 */
 
 			/* puzzle.configを一括で扱うため登録 */
@@ -264,11 +269,11 @@
 			}
 
 			try {
-				localStorage.setItem(
+				pzpr.util.store(
 					"pzprv3_config:puzzle",
 					JSON.stringify(ui.puzzle.saveConfig())
 				);
-				localStorage.setItem("pzprv3_config:ui", JSON.stringify(this.getAll()));
+				pzpr.util.store("pzprv3_config:ui", JSON.stringify(this.getAll()));
 			} catch (ex) {
 				console.warn(ex);
 			}
@@ -336,6 +341,15 @@
 		// config.configevent()  設定変更時の動作を記述する (modeはlistener.onModeChangeで変更)
 		//---------------------------------------------------------------------------
 		configevent: function(idname, newval) {
+			//Need to set save icon visibility here to make sure it goes off before the early exit
+			if (idname === "autosave") {
+				var saveIcon = document.getElementById("saveicon");
+				if (!!newval) {
+					saveIcon.classList.remove("hide");
+				} else {
+					saveIcon.classList.add("hide");
+				}
+			}
 			if (!ui.menuarea.menuitem) {
 				return;
 			}
diff --git a/src-ui/p.html b/src-ui/p.html
index 63ca8a2d1..dfd0e94b9 100644
--- a/src-ui/p.html
+++ b/src-ui/p.html
@@ -93,6 +93,7 @@ <h2 id="title2">読み込み中です...</h2>
      <li class="check" data-config="lattice"><span>__lattice.menu__</span></li>
      <li class="check" data-config="singlenum"><span>__singlenum.menu__</span></li>
      <li class="check" data-config="discolor"><span>__discolor__</span></li>
+     <li class="check" data-config="autosave"><span>__autosave__</span></li>
      <li data-config="autocheck_mode"><span>__autocheck__</span>&nbsp;-&gt;<menu label="__autocheck__">
        <li class="child" data-value="off"><span>__autocheck.off__</span></li>
        <li class="child" data-value="guarded"><span>__autocheck.guarded__</span></li>
@@ -111,6 +112,7 @@ <h2 id="title2">読み込み中です...</h2>
      <li class="link"><a target="_blank" href="https://hosted.weblate.org/projects/pzprjs/">__translate__</a></li>
      <li class="link"><a target="_blank" href="https://github.com/robx/pzprjs/issues">__issues__</a></li>
    </menu></li>
+   <div id="saveicon" class="hide">&#x1F4BE</div>
   </menu>
   <div id="usepanel" style="display:none;">
     <div class="config" data-config="mode">
diff --git a/src-ui/res/p.en.json b/src-ui/res/p.en.json
index c185c814f..5984d7e89 100644
--- a/src-ui/res/p.en.json
+++ b/src-ui/res/p.en.json
@@ -57,6 +57,7 @@
     "autocheck.off": "Manual",
     "autocheck.guarded": "Automatic (guarded)",
     "autocheck.simple": "Automatic (always)",
+    "autosave": "Autosave board state [beta]",
     "menu_help": "Help",
     "rules": "Rules",
     "about": "About puzz.link",
diff --git a/src-ui/res/p.ja.json b/src-ui/res/p.ja.json
index 5c52a7851..0ffb5c504 100644
--- a/src-ui/res/p.ja.json
+++ b/src-ui/res/p.ja.json
@@ -56,6 +56,7 @@
     "autocheck.off": "正答を自動で判定しない",
     "autocheck.guarded": "自動(guarded)",
     "autocheck.simple": "自動(常に)",
+    "autosave": "Autosave board state [beta]",
     "menu_help": "ヘルプ",
     "rules": "ルール",
     "about": "puzz.linkについて",
diff --git a/src/pzpr/env.js b/src/pzpr/env.js
index 4a23ec3a3..61ee9041b 100644
--- a/src/pzpr/env.js
+++ b/src/pzpr/env.js
@@ -64,13 +64,25 @@ pzpr.env = (function() {
 		anchor_download:
 			isbrowser && document.createElement("a").download !== void 0
 	};
+	//Taken directly from stackoverflow. Apparently this is the most broadly compatible version. https://stackoverflow.com/questions/16427636/check-if-localstorage-is-available
+	var localStorageAvailable = (function() {
+		var test = "test";
+		try {
+			localStorage.setItem(test, test);
+			localStorage.removeItem(test);
+			return true;
+		} catch (e) {
+			return false;
+		}
+	})();
 
 	return {
 		bz: bz,
 		OS: os,
 		API: api,
 		browser: isbrowser,
-		node: pzpr.Candle.env.node
+		node: pzpr.Candle.env.node,
+		localStorageAvailable: localStorageAvailable
 	};
 })();
 
diff --git a/src/pzpr/util.js b/src/pzpr/util.js
index 28ee66321..4c0576a6e 100644
--- a/src/pzpr/util.js
+++ b/src/pzpr/util.js
@@ -220,6 +220,39 @@
 				}
 			}
 			return true;
+		},
+
+		// "Safe" set to local storage. Catches quota exceeded errors and removes the oldest puzzles.
+		// Separated here so that settings can be set safely as well
+		store: function(key, value) {
+			try {
+				localStorage.setItem(key, value);
+			} catch (e) {
+				if (e.name === "QuotaExceededError") {
+					//If storage was full: load all of the puzzles in localStorage, sort by least recent, and delete until saving is successful
+					var pairs = [];
+					for (var i = 0; i < localStorage.length; i++) {
+						var lsKey = localStorage.key(i);
+						var lsValue = JSON.parse(localStorage.getItem(lsKey));
+						if (lsKey.indexOf("pzpr_") === 0) {
+							pairs.push({ key: lsKey, value: lsValue });
+						}
+					}
+					pairs.sort(function(a, b) {
+						var ta = a.value.t;
+						var tb = b.value.t;
+						return ta - tb;
+					});
+					for (var i = 0; i < pairs.length; i++) {
+						try {
+							localStorage.setItem(key, value);
+							break;
+						} catch (e) {
+							localStorage.removeItem(pairs[i].key);
+						}
+					}
+				}
+			}
 		}
 	};
 })();