diff --git a/extensions/vscode-api-tests/src/singlefolder-tests/notebook.test.ts b/extensions/vscode-api-tests/src/singlefolder-tests/notebook.test.ts
index 293913f62a1..f3bc83e7fb3 100644
--- a/extensions/vscode-api-tests/src/singlefolder-tests/notebook.test.ts
+++ b/extensions/vscode-api-tests/src/singlefolder-tests/notebook.test.ts
@@ -61,13 +61,13 @@ class Kernel {
 		task.executionOrder = 1;
 		if (cell.notebook.uri.path.endsWith('customRenderer.vsctestnb')) {
 			await task.replaceOutput([new vscode.NotebookCellOutput([
-				vscode.NotebookCellOutputItem.text('test', 'text/custom', undefined)
+				vscode.NotebookCellOutputItem.text('test', 'text/custom')
 			])]);
 			return;
 		}
 
 		await task.replaceOutput([new vscode.NotebookCellOutput([
-			vscode.NotebookCellOutputItem.text('my output', 'text/plain', undefined)
+			vscode.NotebookCellOutputItem.text('my output', 'text/plain')
 		])]);
 		task.end({ success: true });
 	}
@@ -130,9 +130,12 @@ suite('Notebook API tests', function () {
 							kind: vscode.NotebookCellKind.Code,
 							outputs: [
 								new vscode.NotebookCellOutput([
-									vscode.NotebookCellOutputItem.text('Hello World', 'text/plain', { testOutputItemMetadata: true })
+									vscode.NotebookCellOutputItem.text('Hello World', 'text/plain')
 								],
-									{ testOutputMetadata: true })
+									{
+										testOutputMetadata: true,
+										['text/plain']: { testOutputItemMetadata: true }
+									})
 							],
 							executionSummary: { executionOrder: 5, success: true },
 							metadata: new vscode.NotebookCellMetadata().with({ custom: { testCellMetadata: 456 } })
@@ -183,7 +186,7 @@ suite('Notebook API tests', function () {
 				const task = this.controller.createNotebookCellExecution(cell);
 				task.start();
 				await task.replaceOutput([new vscode.NotebookCellOutput([
-					vscode.NotebookCellOutputItem.text('my second output', 'text/plain', undefined)
+					vscode.NotebookCellOutputItem.text('my second output', 'text/plain')
 				])]);
 				task.end({ success: true });
 			}
@@ -474,12 +477,11 @@ suite('Notebook API tests', function () {
 
 		const secondCell = vscode.window.activeNotebookEditor!.document.cellAt(1);
 		assert.strictEqual(secondCell!.outputs.length, 1);
-		assert.deepStrictEqual(secondCell!.outputs[0].metadata, { testOutputMetadata: true });
+		assert.deepStrictEqual(secondCell!.outputs[0].metadata, { testOutputMetadata: true, ['text/plain']: { testOutputItemMetadata: true } });
 		assert.strictEqual((<any>secondCell!.outputs[0]).outputs.length, 1); //todo@jrieken will FAIL once the backwards compatibility is gone
 		assert.strictEqual(secondCell!.outputs[0].items.length, 1);
 		assert.strictEqual(secondCell!.outputs[0].items[0].mime, 'text/plain');
 		assert.strictEqual(new TextDecoder().decode(secondCell!.outputs[0].items[0].data), 'Hello World');
-		assert.deepStrictEqual(secondCell!.outputs[0].items[0].metadata, { testOutputItemMetadata: true });
 		assert.strictEqual(secondCell!.executionSummary?.executionOrder, 5);
 		assert.strictEqual(secondCell!.executionSummary?.success, true);
 
@@ -777,7 +779,7 @@ suite('Notebook API tests', function () {
 					task.start();
 					task.token.onCancellationRequested(async () => {
 						await task.replaceOutput([new vscode.NotebookCellOutput([
-							vscode.NotebookCellOutputItem.text('Canceled', 'text/plain', undefined)
+							vscode.NotebookCellOutputItem.text('Canceled', 'text/plain')
 						])]);
 						task.end({});
 					});
@@ -822,7 +824,7 @@ suite('Notebook API tests', function () {
 
 			async interrupt() {
 				await this._task!.replaceOutput([new vscode.NotebookCellOutput([
-					vscode.NotebookCellOutputItem.text('Interrupted', 'text/plain', undefined)
+					vscode.NotebookCellOutputItem.text('Interrupted', 'text/plain')
 				])]);
 				this._task!.end({});
 			}
@@ -1182,7 +1184,7 @@ suite('Notebook API tests', function () {
 				const task = this.controller.createNotebookCellExecution(cell);
 				task.start();
 				await task.replaceOutput([new vscode.NotebookCellOutput([
-					vscode.NotebookCellOutputItem.text('Some output', 'text/plain', undefined)
+					vscode.NotebookCellOutputItem.text('Some output', 'text/plain')
 				])]);
 				assert.strictEqual(cell.notebook.cellAt(0).outputs.length, 1);
 				assert.deepStrictEqual(new TextDecoder().decode(cell.notebook.cellAt(0).outputs[0].items[0].data), 'Some output');
diff --git a/src/vs/vscode.d.ts b/src/vs/vscode.d.ts
index 2e4b0364460..7d724feffd1 100644
--- a/src/vs/vscode.d.ts
+++ b/src/vs/vscode.d.ts
@@ -11578,10 +11578,9 @@ declare module 'vscode' {
 		 *
 		 * @param value A string.
 		 * @param mime Optional MIME type, defaults to `text/plain`.
-		 * @param metadata Optional metadata.
 		 * @returns A new output item object.
 		 */
-		static text(value: string, mime?: string, metadata?: { [key: string]: any }): NotebookCellOutputItem;
+		static text(value: string, mime?: string): NotebookCellOutputItem;
 
 		/**
 		 * Factory function to create a `NotebookCellOutputItem` from
@@ -11593,40 +11592,36 @@ declare module 'vscode' {
 		 *
 		 * @param value A JSON-stringifyable value.
 		 * @param mime Optional MIME type, defaults to `application/json`
-		 * @param metadata Optional metadata.
 		 * @returns A new output item object.
 		 */
-		static json(value: any, mime?: string, metadata?: { [key: string]: any }): NotebookCellOutputItem;
+		static json(value: any, mime?: string): NotebookCellOutputItem;
 
 		/**
 		 * Factory function to create a `NotebookCellOutputItem` that uses
 		 * uses the `application/vnd.code.notebook.stdout` mime type.
 		 *
 		 * @param value A string.
-		 * @param metadata Optional metadata.
 		 * @returns A new output item object.
 		 */
-		static stdout(value: string, metadata?: { [key: string]: any }): NotebookCellOutputItem;
+		static stdout(value: string): NotebookCellOutputItem;
 
 		/**
 		 * Factory function to create a `NotebookCellOutputItem` that uses
 		 * uses the `application/vnd.code.notebook.stderr` mime type.
 		 *
 		 * @param value A string.
-		 * @param metadata Optional metadata.
 		 * @returns A new output item object.
 		 */
-		static stderr(value: string, metadata?: { [key: string]: any }): NotebookCellOutputItem;
+		static stderr(value: string): NotebookCellOutputItem;
 
 		/**
 		 * Factory function to create a `NotebookCellOutputItem` that uses
 		 * uses the `application/vnd.code.notebook.error` mime type.
 		 *
 		 * @param value An error object.
-		 * @param metadata Optional metadata.
 		 * @returns A new output item object.
 		 */
-		static error(value: Error, metadata?: { [key: string]: any }): NotebookCellOutputItem;
+		static error(value: Error): NotebookCellOutputItem;
 
 		/**
 		 * The mime type which determines how the {@link NotebookCellOutputItem.value `value`}-property
@@ -11642,17 +11637,13 @@ declare module 'vscode' {
 		 */
 		data: Uint8Array;
 
-		//todo@API remove in favour of NotebookCellOutput#metadata
-		metadata?: { [key: string]: any };
-
 		/**
 		 * Create a new notbook cell output item.
 		 *
 		 * @param data The value of the output item.
 		 * @param mime The mime type of the output item.
-		 * @param metadata Optional metadata for this output item.
 		 */
-		constructor(data: Uint8Array, mime: string, metadata?: { [key: string]: any });
+		constructor(data: Uint8Array, mime: string);
 	}
 
 	/**
@@ -11685,7 +11676,7 @@ declare module 'vscode' {
 		items: NotebookCellOutputItem[];
 
 		/**
-		 * Arbitrary metadata for this cell output. .
+		 * Arbitrary metadata for this cell output. Can be anything but must be JSON-stringifyable.
 		 */
 		metadata?: { [key: string]: any };
 
diff --git a/src/vs/workbench/api/common/extHostTypeConverters.ts b/src/vs/workbench/api/common/extHostTypeConverters.ts
index 2c5ca31f62a..d186b6cf851 100644
--- a/src/vs/workbench/api/common/extHostTypeConverters.ts
+++ b/src/vs/workbench/api/common/extHostTypeConverters.ts
@@ -1535,14 +1535,13 @@ export namespace NotebookCellData {
 export namespace NotebookCellOutputItem {
 	export function from(item: types.NotebookCellOutputItem): notebooks.IOutputItemDto {
 		return {
-			metadata: item.metadata,
 			mime: item.mime,
 			valueBytes: Array.from(item.data), //todo@jrieken this HACKY and SLOW... hoist VSBuffer instead
 		};
 	}
 
 	export function to(item: notebooks.IOutputItemDto): types.NotebookCellOutputItem {
-		return new types.NotebookCellOutputItem(new Uint8Array(item.valueBytes), item.mime, item.metadata);
+		return new types.NotebookCellOutputItem(new Uint8Array(item.valueBytes), item.mime);
 	}
 }
 
diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index 14bafd76896..37e48d92def 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -3116,43 +3116,42 @@ export class NotebookCellOutputItem {
 			&& (<vscode.NotebookCellOutputItem>obj).data instanceof Uint8Array;
 	}
 
-	static error(err: Error | { name: string, message?: string, stack?: string }, metadata?: { [key: string]: any }): NotebookCellOutputItem {
+	static error(err: Error | { name: string, message?: string, stack?: string }): NotebookCellOutputItem {
 		const obj = {
 			name: err.name,
 			message: err.message,
 			stack: err.stack
 		};
-		return NotebookCellOutputItem.json(obj, 'application/vnd.code.notebook.error', metadata);
+		return NotebookCellOutputItem.json(obj, 'application/vnd.code.notebook.error');
 	}
 
-	static stdout(value: string, metadata?: { [key: string]: any }): NotebookCellOutputItem {
-		return NotebookCellOutputItem.text(value, 'application/vnd.code.notebook.stdout', metadata);
+	static stdout(value: string): NotebookCellOutputItem {
+		return NotebookCellOutputItem.text(value, 'application/vnd.code.notebook.stdout');
 	}
 
-	static stderr(value: string, metadata?: { [key: string]: any }): NotebookCellOutputItem {
-		return NotebookCellOutputItem.text(value, 'application/vnd.code.notebook.stderr', metadata);
+	static stderr(value: string): NotebookCellOutputItem {
+		return NotebookCellOutputItem.text(value, 'application/vnd.code.notebook.stderr');
 	}
 
-	static bytes(value: Uint8Array, mime: string = 'application/octet-stream', metadata?: { [key: string]: any }): NotebookCellOutputItem {
-		return new NotebookCellOutputItem(value, mime, metadata);
+	static bytes(value: Uint8Array, mime: string = 'application/octet-stream'): NotebookCellOutputItem {
+		return new NotebookCellOutputItem(value, mime);
 	}
 
 	static #encoder = new TextEncoder();
 
-	static text(value: string, mime: string = 'text/plain', metadata?: { [key: string]: any }): NotebookCellOutputItem {
+	static text(value: string, mime: string = 'text/plain'): NotebookCellOutputItem {
 		const bytes = NotebookCellOutputItem.#encoder.encode(String(value));
-		return new NotebookCellOutputItem(bytes, mime, metadata);
+		return new NotebookCellOutputItem(bytes, mime);
 	}
 
-	static json(value: any, mime: string = 'application/json', metadata?: { [key: string]: any }): NotebookCellOutputItem {
+	static json(value: any, mime: string = 'application/json'): NotebookCellOutputItem {
 		const rawStr = JSON.stringify(value, undefined, '\t');
-		return NotebookCellOutputItem.text(rawStr, mime, metadata);
+		return NotebookCellOutputItem.text(rawStr, mime);
 	}
 
 	constructor(
 		public data: Uint8Array,
 		public mime: string,
-		public metadata?: { [key: string]: any }
 	) {
 		const mimeNormalized = normalizeMimeType(mime, true);
 		if (!mimeNormalized) {
diff --git a/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts b/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
index 2071be77e6f..577e01f2045 100644
--- a/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
+++ b/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
@@ -1523,7 +1523,7 @@ var requirejs = (function() {
 					outputId: output.outputId,
 					mimeType: content.mimeType,
 					valueBytes: new Uint8Array(outputDto?.valueBytes ?? []),
-					metadata: outputDto?.metadata,
+					metadata: output.metadata,
 					metadata2: output.metadata
 				},
 			};
diff --git a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
index a56c0f70456..d0ce1ca8713 100644
--- a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
+++ b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
@@ -174,7 +174,6 @@ export interface IOrderedMimeType {
 export interface IOutputItemDto {
 	readonly mime: string;
 	readonly valueBytes: number[];
-	readonly metadata?: Record<string, unknown>;
 }
 
 export interface IOutputDto {
diff --git a/src/vs/workbench/test/browser/api/extHostTypeConverter.test.ts b/src/vs/workbench/test/browser/api/extHostTypeConverter.test.ts
index 9b9e68a2778..e766008f374 100644
--- a/src/vs/workbench/test/browser/api/extHostTypeConverter.test.ts
+++ b/src/vs/workbench/test/browser/api/extHostTypeConverter.test.ts
@@ -96,7 +96,6 @@ suite('ExtHostTypeConverter', function () {
 		const item2 = NotebookCellOutputItem.to(dto);
 
 		assert.strictEqual(item2.mime, item.mime);
-		assert.strictEqual(item2.metadata, item.metadata);
 		assert.deepStrictEqual(item2.data, item.data);
 	});
 });