diff --git a/server.py b/server.py
index 5be822a6..b0dd3382 100644
--- a/server.py
+++ b/server.py
@@ -217,6 +217,28 @@ class PromptServer():
                 file = os.path.join(output_dir, filename)
 
                 if os.path.isfile(file):
+                    if 'preview' in request.rel_url.query:
+                        with Image.open(file) as img:
+                            preview_info = request.rel_url.query['preview'].split(';')
+
+                            if preview_info[0] == "L" or preview_info[0] == "l":
+                                img = img.convert("L")
+                                image_format = preview_info[1]
+                            else:
+                                img = img.convert("RGB")  # jpeg doesn't support RGBA
+                                image_format = preview_info[0]
+
+                            quality = 90
+                            if preview_info[-1].isdigit():
+                                quality = int(preview_info[-1])
+
+                            buffer = BytesIO()
+                            img.save(buffer, format=image_format, optimize=True, quality=quality)
+                            buffer.seek(0)
+
+                            return web.Response(body=buffer.read(), content_type=f'image/{image_format}',
+                                                headers={"Content-Disposition": f"filename=\"{filename}\""})
+
                     if 'channel' not in request.rel_url.query:
                         channel = 'rgba'
                     else:
diff --git a/web/extensions/core/maskeditor.js b/web/extensions/core/maskeditor.js
index 6cb3a538..764164d5 100644
--- a/web/extensions/core/maskeditor.js
+++ b/web/extensions/core/maskeditor.js
@@ -41,7 +41,7 @@ async function uploadMask(filepath, formData) {
 	});
 
 	ComfyApp.clipspace.imgs[ComfyApp.clipspace['selectedIndex']] = new Image();
-	ComfyApp.clipspace.imgs[ComfyApp.clipspace['selectedIndex']].src = "/view?" + new URLSearchParams(filepath).toString();
+	ComfyApp.clipspace.imgs[ComfyApp.clipspace['selectedIndex']].src = "/view?" + new URLSearchParams(filepath).toString() + app.getPreviewFormatParam();
 
 	if(ComfyApp.clipspace.images)
 		ComfyApp.clipspace.images[ComfyApp.clipspace['selectedIndex']] = filepath;
@@ -335,6 +335,7 @@ class MaskEditorDialog extends ComfyDialog {
 
 		const alpha_url = new URL(ComfyApp.clipspace.imgs[ComfyApp.clipspace['selectedIndex']].src)
 		alpha_url.searchParams.delete('channel');
+		alpha_url.searchParams.delete('preview');
 		alpha_url.searchParams.set('channel', 'a');
 		touched_image.src = alpha_url;
 
@@ -345,6 +346,7 @@ class MaskEditorDialog extends ComfyDialog {
 
 		const rgb_url = new URL(ComfyApp.clipspace.imgs[ComfyApp.clipspace['selectedIndex']].src);
 		rgb_url.searchParams.delete('channel');
+		rgb_url.searchParams.delete('preview');
 		rgb_url.searchParams.set('channel', 'rgb');
 		orig_image.src = rgb_url;
 		this.image = orig_image;
diff --git a/web/scripts/app.js b/web/scripts/app.js
index 8a9c7ca4..95447ffa 100644
--- a/web/scripts/app.js
+++ b/web/scripts/app.js
@@ -51,6 +51,14 @@ export class ComfyApp {
 		this.shiftDown = false;
 	}
 
+	getPreviewFormatParam() {
+		let preview_format = this.ui.settings.getSettingValue("Comfy.PreviewFormat");
+		if(preview_format)
+			return `&preview=${preview_format}`;
+		else
+			return "";
+	}
+
 	static isImageNode(node) {
 		return node.imgs || (node && node.widgets && node.widgets.findIndex(obj => obj.name === 'image') >= 0);
 	}
@@ -231,14 +239,20 @@ export class ComfyApp {
 					options.unshift(
 						{
 							content: "Open Image",
-							callback: () => window.open(img.src, "_blank"),
+							callback: () => {
+								let url = new URL(img.src);
+								url.searchParams.delete('preview');
+								window.open(url, "_blank")
+							},
 						},
 						{
 							content: "Save Image",
 							callback: () => {
 								const a = document.createElement("a");
-								a.href = img.src;
-								a.setAttribute("download", new URLSearchParams(new URL(img.src).search).get("filename"));
+								let url = new URL(img.src);
+								url.searchParams.delete('preview');
+								a.href = url;
+								a.setAttribute("download", new URLSearchParams(url.search).get("filename"));
 								document.body.append(a);
 								a.click();
 								requestAnimationFrame(() => a.remove());
@@ -365,7 +379,7 @@ export class ComfyApp {
 									const img = new Image();
 									img.onload = () => r(img);
 									img.onerror = () => r(null);
-									img.src = "/view?" + new URLSearchParams(src).toString();
+									img.src = "/view?" + new URLSearchParams(src).toString() + app.getPreviewFormatParam();
 								});
 							})
 						).then((imgs) => {
diff --git a/web/scripts/ui.js b/web/scripts/ui.js
index 2c9043d0..6b764d43 100644
--- a/web/scripts/ui.js
+++ b/web/scripts/ui.js
@@ -462,6 +462,25 @@ export class ComfyUI {
 			defaultValue: true,
 		});
 
+		/**
+		 * file format for preview
+		 *
+		 * L?;format;quality
+		 *
+		 * ex)
+		 * L;webp;50 -> grayscale, webp, quality 50
+		 * jpeg;80 -> rgb, jpeg, quality 80
+		 * png -> rgb, png, default quality(=90)
+		 *
+		 * @type {string}
+		 */
+		const previewImage = this.settings.addSetting({
+			id: "Comfy.PreviewFormat",
+			name: "When displaying a preview in the image widget, convert it to a lightweight image. (webp, jpeg, webp;50, ...)",
+			type: "string",
+			defaultValue: "",
+		});
+
 		const fileInput = $el("input", {
 			id: "comfy-file-input",
 			type: "file",
diff --git a/web/scripts/widgets.js b/web/scripts/widgets.js
index 82168b08..d6faaddb 100644
--- a/web/scripts/widgets.js
+++ b/web/scripts/widgets.js
@@ -303,7 +303,7 @@ export const ComfyWidgets = {
 				subfolder = name.substring(0, folder_separator);
 				name = name.substring(folder_separator + 1);
 			}
-			img.src = `/view?filename=${name}&type=input&subfolder=${subfolder}`;
+			img.src = `/view?filename=${name}&type=input&subfolder=${subfolder}${app.getPreviewFormatParam()}`;
 			node.setSizeForImage?.();
 		}