diff --git a/src/lib/state.svelte.ts b/src/lib/state.svelte.ts
index 7c23ff2..50c4a6c 100644
--- a/src/lib/state.svelte.ts
+++ b/src/lib/state.svelte.ts
@@ -1,7 +1,10 @@
 import { SvelteSet } from 'svelte/reactivity';
 import type { Item, Manifest, Asset, AssetStore, Viewport } from './types';
 
-const STORAGE_KEY = 'buboard';
+const DB_NAME = 'buboard';
+const DB_VERSION = 1;
+const STORE_NAME = 'state';
+const LEGACY_STORAGE_KEY = 'buboard';
 
 const DEFAULT_SHARED_CSS = `* {
   box-sizing: border-box;
@@ -39,30 +42,22 @@ const DEFAULT_APP_CSS = `:root {
   --cm-operator: #56b6c2;
 }`;
 
-interface StoredAsset {
-	dataUrl: string;
+interface StoredAssetIndexedDB {
+	blob: Blob;
 	filename: string;
 }
 
-interface StoredState {
-	manifest: Manifest;
-	assets: Record<string, StoredAsset>;
-}
-
-async function blobToDataUrl(blob: Blob): Promise<string> {
+function openDb(): Promise<IDBDatabase> {
 	return new Promise((resolve, reject) => {
-		const reader = new FileReader();
-		reader.onload = () => resolve(reader.result as string);
-		reader.onerror = reject;
-		reader.readAsDataURL(blob);
+		const request = indexedDB.open(DB_NAME, DB_VERSION);
+		request.onerror = () => reject(request.error);
+		request.onsuccess = () => resolve(request.result);
+		request.onupgradeneeded = () => {
+			request.result.createObjectStore(STORE_NAME);
+		};
 	});
 }
 
-async function dataUrlToBlob(dataUrl: string): Promise<Blob> {
-	const res = await fetch(dataUrl);
-	return res.blob();
-}
-
 function createState() {
 	let manifest = $state<Manifest>({
 		version: 1,
@@ -81,6 +76,7 @@ function createState() {
 	let clipboard = $state<Omit<Item, 'id'>[]>([]);
 	let locked = $state<boolean>(false);
 	let snapToGrid = $state<boolean>(false);
+	let persistenceError = $state<string | null>(null);
 
 	const GRID_SIZE = 20;
 
@@ -98,18 +94,25 @@ function createState() {
 			clearTimeout(saveTimeout);
 			saveTimeout = null;
 		}
-		const storedAssets: Record<string, StoredAsset> = {};
-		for (const [id, asset] of Object.entries(assets)) {
-			storedAssets[id] = {
-				dataUrl: await blobToDataUrl(asset.blob),
-				filename: asset.filename,
-			};
-		}
-		const stored: StoredState = { manifest, assets: storedAssets };
 		try {
-			localStorage.setItem(STORAGE_KEY, JSON.stringify(stored));
-		} catch {
-			// localStorage full or unavailable
+			const storedAssets: Record<string, StoredAssetIndexedDB> = {};
+			for (const [id, asset] of Object.entries(assets)) {
+				storedAssets[id] = { blob: asset.blob, filename: asset.filename };
+			}
+			const db = await openDb();
+			const tx = db.transaction(STORE_NAME, 'readwrite');
+			const store = tx.objectStore(STORE_NAME);
+			store.put($state.snapshot(manifest), 'manifest');
+			store.put(storedAssets, 'assets');
+			await new Promise<void>((resolve, reject) => {
+				tx.oncomplete = () => resolve();
+				tx.onerror = () => reject(tx.error);
+			});
+			db.close();
+			persistenceError = null;
+		} catch (e) {
+			persistenceError = e instanceof Error ? e.message : 'Failed to save';
+			throw e;
 		}
 	}
 
@@ -122,29 +125,78 @@ function createState() {
 
 	async function restore() {
 		try {
-			const raw = localStorage.getItem(STORAGE_KEY);
+			const db = await openDb();
+
+			const loadFromDb = (): Promise<{ manifest: Manifest | null; assets: Record<string, StoredAssetIndexedDB> | null }> => {
+				return new Promise((resolve) => {
+					const tx = db.transaction(STORE_NAME, 'readonly');
+					const store = tx.objectStore(STORE_NAME);
+					const manifestReq = store.get('manifest');
+					const assetsReq = store.get('assets');
+					tx.oncomplete = () => {
+						resolve({ manifest: manifestReq.result ?? null, assets: assetsReq.result ?? null });
+					};
+					tx.onerror = () => resolve({ manifest: null, assets: null });
+				});
+			};
+
+			const { manifest: storedManifest, assets: storedAssets } = await loadFromDb();
+			db.close();
+
+			if (storedManifest && storedManifest.version === 1) {
+				const restoredAssets: AssetStore = {};
+				if (storedAssets) {
+					for (const [id, asset] of Object.entries(storedAssets)) {
+						const url = URL.createObjectURL(asset.blob);
+						restoredAssets[id] = { blob: asset.blob, url, filename: asset.filename };
+					}
+				}
+				for (const item of storedManifest.items) {
+					if (item.assetId && restoredAssets[item.assetId]) {
+						const newUrl = restoredAssets[item.assetId].url;
+						item.html = item.html.replace(/src="[^"]*"/g, `src="${newUrl}"`);
+					}
+				}
+				manifest = { ...storedManifest, flags: storedManifest.flags ?? {} };
+				assets = restoredAssets;
+				return;
+			}
+		} catch (e) {
+			console.error('Failed to restore from IndexedDB:', e);
+		}
+
+		// Migration from localStorage
+		try {
+			const raw = localStorage.getItem(LEGACY_STORAGE_KEY);
 			if (!raw) return;
-			const stored: StoredState = JSON.parse(raw);
-			if (stored.manifest.version !== 1) return;
+
+			interface LegacyStoredAsset { dataUrl: string; filename: string; }
+			interface LegacyStoredState { manifest: Manifest; assets: Record<string, LegacyStoredAsset>; }
+
+			const legacy: LegacyStoredState = JSON.parse(raw);
+			if (legacy.manifest.version !== 1) return;
 
 			const restoredAssets: AssetStore = {};
-			for (const [id, storedAsset] of Object.entries(stored.assets)) {
-				const blob = await dataUrlToBlob(storedAsset.dataUrl);
+			for (const [id, legacyAsset] of Object.entries(legacy.assets)) {
+				const blob = await (await fetch(legacyAsset.dataUrl)).blob();
 				const url = URL.createObjectURL(blob);
-				restoredAssets[id] = { blob, url, filename: storedAsset.filename };
+				restoredAssets[id] = { blob, url, filename: legacyAsset.filename };
 			}
 
-			for (const item of stored.manifest.items) {
+			for (const item of legacy.manifest.items) {
 				if (item.assetId && restoredAssets[item.assetId]) {
 					const newUrl = restoredAssets[item.assetId].url;
 					item.html = item.html.replace(/src="[^"]*"/g, `src="${newUrl}"`);
 				}
 			}
 
-			manifest = { ...stored.manifest, flags: stored.manifest.flags ?? {} };
+			manifest = { ...legacy.manifest, flags: legacy.manifest.flags ?? {} };
 			assets = restoredAssets;
-		} catch {
-			// corrupted or missing data
+
+			await saveNow();
+			localStorage.removeItem(LEGACY_STORAGE_KEY);
+		} catch (e) {
+			console.error('Failed to migrate from localStorage:', e);
 		}
 	}
 
@@ -428,7 +480,7 @@ function createState() {
 		editingId = null;
 		editingGlobal = false;
 		focusedId = null;
-		localStorage.removeItem(STORAGE_KEY);
+		indexedDB.deleteDatabase(DB_NAME);
 	}
 
 	async function load(newManifest: Manifest, newAssets: AssetStore): Promise<void> {
@@ -481,6 +533,9 @@ function createState() {
 		get snapToGrid() {
 			return snapToGrid;
 		},
+		get persistenceError() {
+			return persistenceError;
+		},
 		get maxZIndex() {
 			return maxZIndex;
 		},