diff --git a/drizzle/0000_wooden_vargas.sql b/drizzle/0000_wooden_vargas.sql
new file mode 100644
index 0000000..62276f2
--- /dev/null
+++ b/drizzle/0000_wooden_vargas.sql
@@ -0,0 +1,67 @@
+CREATE TABLE `attachments` (
+	`id` text PRIMARY KEY NOT NULL,
+	`note_id` text NOT NULL,
+	`filename` text NOT NULL,
+	`mime_type` text NOT NULL,
+	`size` integer NOT NULL,
+	`path` text NOT NULL,
+	`thumbnail_path` text,
+	`created_at` integer NOT NULL,
+	FOREIGN KEY (`note_id`) REFERENCES `notes`(`id`) ON UPDATE no action ON DELETE cascade
+);
+--> statement-breakpoint
+CREATE TABLE `note_tags` (
+	`note_id` text NOT NULL,
+	`tag_id` integer NOT NULL,
+	FOREIGN KEY (`note_id`) REFERENCES `notes`(`id`) ON UPDATE no action ON DELETE cascade,
+	FOREIGN KEY (`tag_id`) REFERENCES `tags`(`id`) ON UPDATE no action ON DELETE cascade
+);
+--> statement-breakpoint
+CREATE INDEX `note_tags_note_id_idx` ON `note_tags` (`note_id`);--> statement-breakpoint
+CREATE INDEX `note_tags_tag_id_idx` ON `note_tags` (`tag_id`);--> statement-breakpoint
+CREATE TABLE `notes` (
+	`id` text PRIMARY KEY NOT NULL,
+	`title` text DEFAULT '' NOT NULL,
+	`content` text DEFAULT '' NOT NULL,
+	`color` text DEFAULT 'default' NOT NULL,
+	`pinned` integer DEFAULT false NOT NULL,
+	`archived` integer DEFAULT false NOT NULL,
+	`trashed` integer DEFAULT false NOT NULL,
+	`trashed_at` integer,
+	`checklist_mode` integer DEFAULT false NOT NULL,
+	`sort_order` integer DEFAULT 0 NOT NULL,
+	`created_at` integer NOT NULL,
+	`updated_at` integer NOT NULL,
+	`version` integer DEFAULT 1 NOT NULL
+);
+--> statement-breakpoint
+CREATE INDEX `notes_trashed_archived_idx` ON `notes` (`trashed`,`archived`);--> statement-breakpoint
+CREATE INDEX `notes_updated_at_idx` ON `notes` (`updated_at`);--> statement-breakpoint
+CREATE TABLE `sessions` (
+	`id` text PRIMARY KEY NOT NULL,
+	`user_id` integer NOT NULL,
+	`expires_at` integer NOT NULL,
+	FOREIGN KEY (`user_id`) REFERENCES `users`(`id`) ON UPDATE no action ON DELETE no action
+);
+--> statement-breakpoint
+CREATE TABLE `sync_log` (
+	`id` integer PRIMARY KEY AUTOINCREMENT NOT NULL,
+	`note_id` text NOT NULL,
+	`operation` text NOT NULL,
+	`timestamp` integer NOT NULL,
+	`client_id` text NOT NULL,
+	FOREIGN KEY (`note_id`) REFERENCES `notes`(`id`) ON UPDATE no action ON DELETE no action
+);
+--> statement-breakpoint
+CREATE INDEX `sync_log_timestamp_idx` ON `sync_log` (`timestamp`);--> statement-breakpoint
+CREATE TABLE `tags` (
+	`id` integer PRIMARY KEY AUTOINCREMENT NOT NULL,
+	`name` text NOT NULL
+);
+--> statement-breakpoint
+CREATE UNIQUE INDEX `tags_name_unique` ON `tags` (`name`);--> statement-breakpoint
+CREATE TABLE `users` (
+	`id` integer PRIMARY KEY AUTOINCREMENT NOT NULL,
+	`password_hash` text NOT NULL,
+	`created_at` integer NOT NULL
+);
diff --git a/drizzle/meta/0000_snapshot.json b/drizzle/meta/0000_snapshot.json
new file mode 100644
index 0000000..9a47ce4
--- /dev/null
+++ b/drizzle/meta/0000_snapshot.json
@@ -0,0 +1,465 @@
+{
+  "version": "6",
+  "dialect": "sqlite",
+  "id": "682b02aa-a28d-4904-8996-cbc4d740f626",
+  "prevId": "00000000-0000-0000-0000-000000000000",
+  "tables": {
+    "attachments": {
+      "name": "attachments",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "note_id": {
+          "name": "note_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "filename": {
+          "name": "filename",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "mime_type": {
+          "name": "mime_type",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "size": {
+          "name": "size",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "path": {
+          "name": "path",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "thumbnail_path": {
+          "name": "thumbnail_path",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {},
+      "foreignKeys": {
+        "attachments_note_id_notes_id_fk": {
+          "name": "attachments_note_id_notes_id_fk",
+          "tableFrom": "attachments",
+          "tableTo": "notes",
+          "columnsFrom": [
+            "note_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "note_tags": {
+      "name": "note_tags",
+      "columns": {
+        "note_id": {
+          "name": "note_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "tag_id": {
+          "name": "tag_id",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "note_tags_note_id_idx": {
+          "name": "note_tags_note_id_idx",
+          "columns": [
+            "note_id"
+          ],
+          "isUnique": false
+        },
+        "note_tags_tag_id_idx": {
+          "name": "note_tags_tag_id_idx",
+          "columns": [
+            "tag_id"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "note_tags_note_id_notes_id_fk": {
+          "name": "note_tags_note_id_notes_id_fk",
+          "tableFrom": "note_tags",
+          "tableTo": "notes",
+          "columnsFrom": [
+            "note_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        },
+        "note_tags_tag_id_tags_id_fk": {
+          "name": "note_tags_tag_id_tags_id_fk",
+          "tableFrom": "note_tags",
+          "tableTo": "tags",
+          "columnsFrom": [
+            "tag_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "notes": {
+      "name": "notes",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "title": {
+          "name": "title",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "''"
+        },
+        "content": {
+          "name": "content",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "''"
+        },
+        "color": {
+          "name": "color",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "'default'"
+        },
+        "pinned": {
+          "name": "pinned",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": false
+        },
+        "archived": {
+          "name": "archived",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": false
+        },
+        "trashed": {
+          "name": "trashed",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": false
+        },
+        "trashed_at": {
+          "name": "trashed_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "checklist_mode": {
+          "name": "checklist_mode",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": false
+        },
+        "sort_order": {
+          "name": "sort_order",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": 0
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "updated_at": {
+          "name": "updated_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "version": {
+          "name": "version",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": 1
+        }
+      },
+      "indexes": {
+        "notes_trashed_archived_idx": {
+          "name": "notes_trashed_archived_idx",
+          "columns": [
+            "trashed",
+            "archived"
+          ],
+          "isUnique": false
+        },
+        "notes_updated_at_idx": {
+          "name": "notes_updated_at_idx",
+          "columns": [
+            "updated_at"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {},
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "sessions": {
+      "name": "sessions",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "user_id": {
+          "name": "user_id",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "expires_at": {
+          "name": "expires_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {},
+      "foreignKeys": {
+        "sessions_user_id_users_id_fk": {
+          "name": "sessions_user_id_users_id_fk",
+          "tableFrom": "sessions",
+          "tableTo": "users",
+          "columnsFrom": [
+            "user_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "no action",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "sync_log": {
+      "name": "sync_log",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "integer",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": true
+        },
+        "note_id": {
+          "name": "note_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "operation": {
+          "name": "operation",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "timestamp": {
+          "name": "timestamp",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "client_id": {
+          "name": "client_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "sync_log_timestamp_idx": {
+          "name": "sync_log_timestamp_idx",
+          "columns": [
+            "timestamp"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "sync_log_note_id_notes_id_fk": {
+          "name": "sync_log_note_id_notes_id_fk",
+          "tableFrom": "sync_log",
+          "tableTo": "notes",
+          "columnsFrom": [
+            "note_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "no action",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "tags": {
+      "name": "tags",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "integer",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": true
+        },
+        "name": {
+          "name": "name",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "tags_name_unique": {
+          "name": "tags_name_unique",
+          "columns": [
+            "name"
+          ],
+          "isUnique": true
+        }
+      },
+      "foreignKeys": {},
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "users": {
+      "name": "users",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "integer",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": true
+        },
+        "password_hash": {
+          "name": "password_hash",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {},
+      "foreignKeys": {},
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    }
+  },
+  "views": {},
+  "enums": {},
+  "_meta": {
+    "schemas": {},
+    "tables": {},
+    "columns": {}
+  },
+  "internal": {
+    "indexes": {}
+  }
+}
\ No newline at end of file
diff --git a/drizzle/meta/_journal.json b/drizzle/meta/_journal.json
new file mode 100644
index 0000000..377f5a8
--- /dev/null
+++ b/drizzle/meta/_journal.json
@@ -0,0 +1,13 @@
+{
+  "version": "7",
+  "dialect": "sqlite",
+  "entries": [
+    {
+      "idx": 0,
+      "version": "6",
+      "when": 1773000424830,
+      "tag": "0000_wooden_vargas",
+      "breakpoints": true
+    }
+  ]
+}
\ No newline at end of file
diff --git a/src/lib/components/ImageUpload.svelte b/src/lib/components/ImageUpload.svelte
index 3cc047f..35955d2 100644
--- a/src/lib/components/ImageUpload.svelte
+++ b/src/lib/components/ImageUpload.svelte
@@ -1,6 +1,7 @@
 <script lang="ts">
 	import XIcon from 'lucide-svelte/icons/x';
 	import type { Attachment } from '$lib/types/index.js';
+	import { optimizeImage } from '$lib/utils/image-optimize.js';
 
 	interface Props {
 		noteId: string;
@@ -12,17 +13,33 @@
 	let { noteId, attachments = [], onUpload, onRemove }: Props = $props();
 
 	let uploading = $state(false);
+	let optimizing = $state(false);
 	let dragOver = $state(false);
 
 	async function handleFiles(files: FileList | null) {
 		if (!files || !noteId) return;
 
-		uploading = true;
 		for (const file of files) {
 			if (!file.type.startsWith('image/')) continue;
 
+			optimizing = true;
+			let optimized: Blob;
+			let thumbnail: Blob;
+			try {
+				const result = await optimizeImage(file);
+				optimized = result.optimized;
+				thumbnail = result.thumbnail;
+			} catch (err) {
+				console.error('Optimization failed, using original:', err);
+				optimized = file;
+				thumbnail = file;
+			}
+			optimizing = false;
+
+			uploading = true;
 			const formData = new FormData();
-			formData.append('file', file);
+			formData.append('file', new File([optimized], file.name, { type: optimized.type || file.type }));
+			formData.append('thumbnail', new File([thumbnail], `${file.name}_thumb.webp`, { type: 'image/webp' }));
 
 			try {
 				const res = await fetch(`/api/notes/${noteId}/attachments`, {
@@ -36,8 +53,8 @@
 			} catch (err) {
 				console.error('Upload failed:', err);
 			}
+			uploading = false;
 		}
-		uploading = false;
 	}
 
 	function handleDrop(e: DragEvent) {
@@ -59,14 +76,14 @@
 			{#each attachments as attachment}
 				<div class="group relative">
 					<img
-						src="/api/notes/{noteId}/attachments/{attachment.id}"
+						src="/api/notes/{noteId}/attachments?attachmentId={attachment.id}"
 						alt={attachment.filename}
 						class="h-20 w-20 rounded-sm object-cover"
 						data-testid="attachment-thumbnail"
 					/>
 					<button
 						onclick={() => onRemove(attachment.id)}
-						class="absolute -right-1 -top-1 hidden rounded-full bg-red-500 p-0.5 text-white group-hover:block"
+						class="absolute -right-1 -top-1 hidden rounded-full bg-[var(--destructive)] p-0.5 text-white group-hover:block"
 						aria-label="Remove attachment"
 						data-testid="remove-attachment"
 					>
@@ -87,7 +104,9 @@
 		tabindex="0"
 		data-testid="upload-dropzone"
 	>
-		{#if uploading}
+		{#if optimizing}
+			<p class="text-sm text-[var(--text-muted)]">Optimizing...</p>
+		{:else if uploading}
 			<p class="text-sm text-[var(--text-muted)]">Uploading...</p>
 		{:else}
 			<label class="cursor-pointer">
diff --git a/src/lib/server/attachments.ts b/src/lib/server/attachments.ts
index 52cc2e3..74ce4f8 100644
--- a/src/lib/server/attachments.ts
+++ b/src/lib/server/attachments.ts
@@ -4,7 +4,8 @@ import { join } from 'path';
 import { v4 as uuidv4 } from 'uuid';
 import { db } from './db/index.js';
 import { attachments } from './db/schema.js';
-import { eq } from 'drizzle-orm';
+import { eq, inArray } from 'drizzle-orm';
+import type { Attachment } from '$lib/types/index.js';
 
 const DATA_DIR = process.env.DATA_DIR || './data';
 const ATTACHMENTS_DIR = join(DATA_DIR, 'attachments');
@@ -16,7 +17,8 @@ if (!existsSync(ATTACHMENTS_DIR)) {
 
 export async function saveAttachment(
 	noteId: string,
-	file: File
+	file: File,
+	thumbnail?: File | Blob | null
 ): Promise<typeof attachments.$inferSelect> {
 	const id = uuidv4();
 	const ext = file.name.split('.').pop() || 'bin';
@@ -26,6 +28,14 @@ export async function saveAttachment(
 	const buffer = Buffer.from(await file.arrayBuffer());
 	await writeFile(filePath, buffer);
 
+	let thumbnailPath: string | null = null;
+	if (thumbnail) {
+		const thumbFilename = `${id}_thumb.webp`;
+		thumbnailPath = join(ATTACHMENTS_DIR, thumbFilename);
+		const thumbBuffer = Buffer.from(await thumbnail.arrayBuffer());
+		await writeFile(thumbnailPath, thumbBuffer);
+	}
+
 	const [attachment] = await db
 		.insert(attachments)
 		.values({
@@ -35,6 +45,7 @@ export async function saveAttachment(
 			mimeType: file.type,
 			size: file.size,
 			path: filePath,
+			thumbnailPath,
 			createdAt: new Date()
 		})
 		.returning();
@@ -42,6 +53,31 @@ export async function saveAttachment(
 	return attachment;
 }
 
+/**
+ * Batch fetch attachments for multiple notes in a single query.
+ * Returns a Map of noteId → Attachment[].
+ */
+export function fetchAttachmentsForNotes(noteIds: string[]): Map<string, Attachment[]> {
+	if (noteIds.length === 0) return new Map();
+
+	const rows = db
+		.select()
+		.from(attachments)
+		.where(inArray(attachments.noteId, noteIds))
+		.all();
+
+	const map = new Map<string, Attachment[]>();
+	for (const row of rows) {
+		const existing = map.get(row.noteId);
+		if (existing) {
+			existing.push(row as Attachment);
+		} else {
+			map.set(row.noteId, [row as Attachment]);
+		}
+	}
+	return map;
+}
+
 export async function getAttachment(id: string) {
 	return db.select().from(attachments).where(eq(attachments.id, id)).get();
 }
@@ -58,6 +94,13 @@ export async function deleteAttachment(id: string) {
 		} catch {
 			// File may already be deleted
 		}
+		if (attachment.thumbnailPath) {
+			try {
+				await unlink(attachment.thumbnailPath);
+			} catch {
+				// Thumbnail may already be deleted
+			}
+		}
 		await db.delete(attachments).where(eq(attachments.id, id));
 	}
 }
diff --git a/src/lib/server/db/schema.ts b/src/lib/server/db/schema.ts
index 78abb53..1eb52f8 100644
--- a/src/lib/server/db/schema.ts
+++ b/src/lib/server/db/schema.ts
@@ -71,6 +71,7 @@ export const attachments = sqliteTable('attachments', {
 	mimeType: text('mime_type').notNull(),
 	size: integer('size').notNull(),
 	path: text('path').notNull(),
+	thumbnailPath: text('thumbnail_path'),
 	createdAt: integer('created_at', { mode: 'timestamp' }).notNull()
 });
 
diff --git a/src/lib/types/index.ts b/src/lib/types/index.ts
index 9f54a66..a08a328 100644
--- a/src/lib/types/index.ts
+++ b/src/lib/types/index.ts
@@ -42,6 +42,7 @@ export interface Attachment {
 	mimeType: string;
 	size: number;
 	path: string;
+	thumbnailPath?: string | null;
 	createdAt: Date;
 }
 
diff --git a/src/lib/utils/image-optimize.ts b/src/lib/utils/image-optimize.ts
new file mode 100644
index 0000000..daea36a
--- /dev/null
+++ b/src/lib/utils/image-optimize.ts
@@ -0,0 +1,124 @@
+const MAX_DIMENSION = 1920;
+const THUMB_SIZE = 200;
+const QUALITY = 0.8;
+const THUMB_QUALITY = 0.6;
+const SKIP_THRESHOLD = 200 * 1024; // 200KB
+
+interface OptimizeResult {
+	optimized: Blob;
+	thumbnail: Blob;
+}
+
+/**
+ * Check if a PNG has transparency by examining the alpha channel.
+ * Reads a sample of pixels to determine if any are non-opaque.
+ */
+function hasTransparency(canvas: HTMLCanvasElement | OffscreenCanvas, ctx: CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D, width: number, height: number): boolean {
+	const imageData = ctx.getImageData(0, 0, width, height);
+	const data = imageData.data;
+	// Check every 4th value (alpha channel) with stride for performance
+	const stride = Math.max(1, Math.floor(data.length / (4 * 10000))) * 4;
+	for (let i = 3; i < data.length; i += stride) {
+		if (data[i] < 255) return true;
+	}
+	return false;
+}
+
+function createCanvas(width: number, height: number): { canvas: HTMLCanvasElement | OffscreenCanvas; ctx: CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D } {
+	if (typeof OffscreenCanvas !== 'undefined') {
+		const canvas = new OffscreenCanvas(width, height);
+		const ctx = canvas.getContext('2d')!;
+		return { canvas, ctx };
+	}
+	const canvas = document.createElement('canvas');
+	canvas.width = width;
+	canvas.height = height;
+	const ctx = canvas.getContext('2d')!;
+	return { canvas, ctx };
+}
+
+async function canvasToBlob(canvas: HTMLCanvasElement | OffscreenCanvas, type: string, quality: number): Promise<Blob> {
+	if (canvas instanceof OffscreenCanvas) {
+		return canvas.convertToBlob({ type, quality });
+	}
+	return new Promise((resolve) => {
+		canvas.toBlob((blob) => resolve(blob!), type, quality);
+	});
+}
+
+async function loadImage(file: File): Promise<HTMLImageElement> {
+	return new Promise((resolve, reject) => {
+		const img = new Image();
+		img.onload = () => {
+			URL.revokeObjectURL(img.src);
+			resolve(img);
+		};
+		img.onerror = reject;
+		img.src = URL.createObjectURL(file);
+	});
+}
+
+function fitDimensions(width: number, height: number, maxDim: number): { width: number; height: number } {
+	if (width <= maxDim && height <= maxDim) return { width, height };
+	const ratio = Math.min(maxDim / width, maxDim / height);
+	return {
+		width: Math.round(width * ratio),
+		height: Math.round(height * ratio)
+	};
+}
+
+/**
+ * Optimize an image file for upload:
+ * - Resize to fit within 1920x1920 (preserve aspect ratio)
+ * - Skip optimization if already < 200KB and within size limits
+ * - Compress JPEG/WebP to ~80% quality
+ * - Convert non-transparent PNG/BMP to WebP; keep transparent PNG as PNG
+ * - Pass GIF/SVG through unmodified
+ * - Generate a 200x200 thumbnail at 60% quality WebP
+ */
+export async function optimizeImage(file: File): Promise<OptimizeResult> {
+	const type = file.type;
+
+	// GIF and SVG pass through unmodified (but still generate thumbnail for GIF)
+	if (type === 'image/svg+xml') {
+		return { optimized: file, thumbnail: file };
+	}
+
+	const img = await loadImage(file);
+	const { width, height } = img;
+
+	// Generate thumbnail
+	const thumbDims = fitDimensions(width, height, THUMB_SIZE);
+	const { canvas: thumbCanvas, ctx: thumbCtx } = createCanvas(thumbDims.width, thumbDims.height);
+	thumbCtx.drawImage(img, 0, 0, thumbDims.width, thumbDims.height);
+	const thumbnail = await canvasToBlob(thumbCanvas, 'image/webp', THUMB_QUALITY);
+
+	// GIF: pass original through but use generated thumbnail
+	if (type === 'image/gif') {
+		return { optimized: file, thumbnail };
+	}
+
+	// Check if optimization can be skipped
+	const fittedDims = fitDimensions(width, height, MAX_DIMENSION);
+	const needsResize = fittedDims.width !== width || fittedDims.height !== height;
+
+	if (!needsResize && file.size < SKIP_THRESHOLD) {
+		return { optimized: file, thumbnail };
+	}
+
+	// Draw at target size
+	const { canvas, ctx } = createCanvas(fittedDims.width, fittedDims.height);
+	ctx.drawImage(img, 0, 0, fittedDims.width, fittedDims.height);
+
+	// Determine output format
+	let outputType = 'image/webp';
+	let quality = QUALITY;
+
+	if (type === 'image/png' && hasTransparency(canvas, ctx, fittedDims.width, fittedDims.height)) {
+		outputType = 'image/png';
+		quality = 1; // PNG is lossless, quality param ignored but set for clarity
+	}
+
+	const optimized = await canvasToBlob(canvas, outputType, quality);
+	return { optimized, thumbnail };
+}
diff --git a/src/routes/api/notes/+server.ts b/src/routes/api/notes/+server.ts
index b01b0c2..d8d33c0 100644
--- a/src/routes/api/notes/+server.ts
+++ b/src/routes/api/notes/+server.ts
@@ -6,6 +6,7 @@ import { eq, and, desc } from 'drizzle-orm';
 import { v4 as uuidv4 } from 'uuid';
 import { extractTags } from '$lib/utils/tags.js';
 import { fetchTagsForNotes, syncNoteTags } from '$lib/server/tags.js';
+import { fetchAttachmentsForNotes } from '$lib/server/attachments.js';
 
 export const GET: RequestHandler = async ({ url }) => {
 	const filter = url.searchParams.get('filter') || 'all';
@@ -29,10 +30,13 @@ export const GET: RequestHandler = async ({ url }) => {
 		.orderBy(desc(notes.pinned), desc(notes.updatedAt))
 		.all();
 
-	const tagMap = fetchTagsForNotes(result.map((n) => n.id));
+	const noteIds = result.map((n) => n.id);
+	const tagMap = fetchTagsForNotes(noteIds);
+	const attachmentMap = fetchAttachmentsForNotes(noteIds);
 	const notesWithTags = result.map((note) => ({
 		...note,
-		tags: tagMap.get(note.id) ?? []
+		tags: tagMap.get(note.id) ?? [],
+		attachments: attachmentMap.get(note.id) ?? []
 	}));
 
 	return json(notesWithTags);
diff --git a/src/routes/api/notes/[id]/+server.ts b/src/routes/api/notes/[id]/+server.ts
index 918aacc..9e02326 100644
--- a/src/routes/api/notes/[id]/+server.ts
+++ b/src/routes/api/notes/[id]/+server.ts
@@ -5,6 +5,7 @@ import { notes } from '$lib/server/db/schema.js';
 import { eq } from 'drizzle-orm';
 import { extractTags } from '$lib/utils/tags.js';
 import { fetchTagsForNotes, syncNoteTags } from '$lib/server/tags.js';
+import { fetchAttachmentsForNotes } from '$lib/server/attachments.js';
 
 export const GET: RequestHandler = async ({ params }) => {
 	const note = db.select().from(notes).where(eq(notes.id, params.id)).get();
@@ -14,8 +15,13 @@ export const GET: RequestHandler = async ({ params }) => {
 	}
 
 	const tagMap = fetchTagsForNotes([note.id]);
+	const attachmentMap = fetchAttachmentsForNotes([note.id]);
 
-	return json({ ...note, tags: tagMap.get(note.id) ?? [] });
+	return json({
+		...note,
+		tags: tagMap.get(note.id) ?? [],
+		attachments: attachmentMap.get(note.id) ?? []
+	});
 };
 
 export const PATCH: RequestHandler = async ({ params, request }) => {
@@ -55,8 +61,13 @@ export const PATCH: RequestHandler = async ({ params, request }) => {
 	}
 
 	const tagMap = fetchTagsForNotes([params.id]);
+	const attachmentMap = fetchAttachmentsForNotes([params.id]);
 
-	return json({ ...updated, tags: tagMap.get(params.id) ?? [] });
+	return json({
+		...updated,
+		tags: tagMap.get(params.id) ?? [],
+		attachments: attachmentMap.get(params.id) ?? []
+	});
 };
 
 export const DELETE: RequestHandler = async ({ params }) => {
diff --git a/src/routes/api/notes/[id]/attachments/+server.ts b/src/routes/api/notes/[id]/attachments/+server.ts
index 1c05c70..461ee04 100644
--- a/src/routes/api/notes/[id]/attachments/+server.ts
+++ b/src/routes/api/notes/[id]/attachments/+server.ts
@@ -10,11 +10,16 @@ export const GET: RequestHandler = async ({ params, url }) => {
 		const attachment = await getAttachment(attachmentId);
 		if (!attachment) throw error(404, 'Attachment not found');
 
-		const buffer = await readFile(attachment.path);
+		const wantThumb = url.searchParams.get('thumb') === '1';
+		const filePath = wantThumb && attachment.thumbnailPath ? attachment.thumbnailPath : attachment.path;
+		const mimeType = wantThumb && attachment.thumbnailPath ? 'image/webp' : attachment.mimeType;
+
+		const buffer = await readFile(filePath);
 		return new Response(buffer, {
 			headers: {
-				'Content-Type': attachment.mimeType,
-				'Content-Disposition': `inline; filename="${attachment.filename}"`
+				'Content-Type': mimeType,
+				'Content-Disposition': `inline; filename="${attachment.filename}"`,
+				'Cache-Control': 'public, max-age=31536000, immutable'
 			}
 		});
 	}
@@ -40,7 +45,8 @@ export const POST: RequestHandler = async ({ params, request }) => {
 		throw error(400, 'File too large (max 10MB)');
 	}
 
-	const attachment = await saveAttachment(params.id, file);
+	const thumbnail = formData.get('thumbnail') as File | null;
+	const attachment = await saveAttachment(params.id, file, thumbnail);
 	return json(attachment, { status: 201 });
 };
 
diff --git a/src/routes/api/sync/+server.ts b/src/routes/api/sync/+server.ts
index f96ea8d..5090c8a 100644
--- a/src/routes/api/sync/+server.ts
+++ b/src/routes/api/sync/+server.ts
@@ -2,6 +2,7 @@ import { json } from '@sveltejs/kit';
 import type { RequestHandler } from './$types.js';
 import { processSyncPush, getChangesSince } from '$lib/sync/server.js';
 import { fetchTagsForNotes } from '$lib/server/tags.js';
+import { fetchAttachmentsForNotes } from '$lib/server/attachments.js';
 
 export const POST: RequestHandler = async ({ request }) => {
 	const { changes } = await request.json();
@@ -18,10 +19,13 @@ export const GET: RequestHandler = async ({ url }) => {
 	const since = parseInt(url.searchParams.get('since') || '0', 10);
 	const changes = await getChangesSince(since);
 
-	const tagMap = fetchTagsForNotes(changes.map((n) => n.id));
+	const noteIds = changes.map((n) => n.id);
+	const tagMap = fetchTagsForNotes(noteIds);
+	const attachmentMap = fetchAttachmentsForNotes(noteIds);
 	const changesWithTags = changes.map((note) => ({
 		...note,
-		tags: tagMap.get(note.id) ?? []
+		tags: tagMap.get(note.id) ?? [],
+		attachments: attachmentMap.get(note.id) ?? []
 	}));
 
 	return json(changesWithTags);