diff --git a/__init__.py b/__init__.py
index 9e7e571..77f3cb5 100644
--- a/__init__.py
+++ b/__init__.py
@@ -182,6 +182,7 @@ def ui_rules():
         Rule("model-preview-fallback-search-safetensors-thumbnail", False, bool),
         Rule("model-show-add-button", True, bool),
         Rule("model-show-copy-button", True, bool),
+        Rule("model-preview-thumbnail-type", "JPEG/WEBP", str),
         Rule("model-add-embedding-extension", False, bool),
         Rule("model-add-drag-strict-on-field", False, bool),
         Rule("model-add-offset", 25, int),
@@ -290,6 +291,16 @@ def image_format_is_equal(f1, f2):
     return f1 == f2 or (f1 == "JPG" and f2 == "JPEG") or (f1 == "JPEG" and f2 == "JPG")
 
 
+def is_auto_thumbnail_format(format):
+    return format in ["JPEG/WEBP", "WEBP/JPEG", "JPG/WEBP", "WEBP/JPG"]
+
+
+def get_auto_thumbnail_format(original_format):
+    if original_format in ["JPEG", "WEBP", "JPG"]:
+        return original_format
+    return "JPEG" # default fallback
+
+
 @server.PromptServer.instance.routes.get("/model-manager/preview/get")
 async def get_model_preview(request):
     uri = request.query.get("uri")
@@ -339,10 +350,13 @@ async def get_model_preview(request):
             image_format = image.format
             if response_image_format is None:
                 response_image_format = image_format
-            elif not image_format_is_equal(response_image_format, image_format):
+            elif is_auto_thumbnail_format(response_image_format):
+                response_image_format = get_auto_thumbnail_format(image_format)
+
+            if not image_format_is_equal(response_image_format, image_format):
                 exif = image.getexif()
                 metadata = get_image_info(image)
-                if response_image_format == 'JPEG' or response_image_format == 'JPG':
+                if response_image_format in ['JPEG', 'JPG']:
                     image = image.convert('RGB')
                 image_bytes = io.BytesIO()
                 image.save(image_bytes, format=response_image_format, exif=exif, pnginfo=metadata, quality=quality)
@@ -358,6 +372,9 @@ async def get_model_preview(request):
             image_format = image.format
             if response_image_format is None:
                 response_image_format = image_format
+            elif is_auto_thumbnail_format(response_image_format):
+                response_image_format = get_auto_thumbnail_format(image_format)
+
             w0, h0 = image.size
             if w is None:
                 w = (h * w0) // h0
@@ -387,13 +404,14 @@ async def get_model_preview(request):
                 resampling_method = Image.Resampling.BICUBIC
             image.thumbnail((w, h), resample=resampling_method)
 
-            if not image_format_is_equal(image_format, response_image_format) and (response_image_format == 'JPEG' or response_image_format == 'JPG'):
+            if not image_format_is_equal(image_format, response_image_format) and response_image_format in ['JPEG', 'JPG']:
                 image = image.convert('RGB')
             image_bytes = io.BytesIO()
             image.save(image_bytes, format=response_image_format, exif=exif, pnginfo=metadata, quality=quality)
             image_data = image_bytes.getvalue()
 
     response_file_name = os.path.splitext(file_name)[0] + '.' + response_image_format.lower()
+    print(f"response_file_name: {response_file_name}")
     return web.Response(
         headers={
             "Content-Disposition": f"inline; filename={response_file_name}",
diff --git a/web/model-manager.js b/web/model-manager.js
index a85e279..4882206 100644
--- a/web/model-manager.js
+++ b/web/model-manager.js
@@ -138,7 +138,6 @@ function imageUri(imageSearchPath = undefined, dateImageModified = undefined, wi
 const PREVIEW_NONE_URI = imageUri();
 const PREVIEW_THUMBNAIL_WIDTH = 320;
 const PREVIEW_THUMBNAIL_HEIGHT = 480;
-const PREVIEW_THUMBNAIL_FORMAT = "JPEG";
 
 /**
  * @param {(...args) => void} callback
@@ -230,6 +229,28 @@ function $checkbox(x = { $: (el) => {}, textContent: "", checked: false }) {
     return label;
 }
 
+/**
+ * @returns {HTMLLabelElement}
+ */
+function $select(x = { $: (el) => {}, textContent: "", options: [""] }) {
+    const text = x.textContent;
+    const select = $el("select", {
+        name: text ?? "select",
+    }, x.options.map((option) => {
+        return $el("option", {
+            value: option,
+        }, option);
+    }));
+    const label = $el("label", [
+        select, 
+        text === "" || text === undefined || text === null ? "" : " " + text,
+    ]);
+    if (x.$ !== undefined){
+        x.$(select);
+    }
+    return label;
+}
+
 /**
  * @param {Any} attr
  * @returns {HTMLDivElement}
@@ -1654,6 +1675,7 @@ class ModelGrid {
         const addOffset = parseInt(settingsElements["model-add-offset"].value);
         const showModelExtension = settingsElements["model-show-label-extensions"].checked;
         const removeEmbeddingExtension = !settingsElements["model-add-embedding-extension"].checked;
+        const previewThumbnailFormat = settingsElements["model-preview-thumbnail-type"].value;
         if (models.length > 0) {
             return models.map((item) => {
                 const previewInfo = item.preview;
@@ -1706,7 +1728,7 @@ class ModelGrid {
                             previewInfo?.dateModified, 
                             PREVIEW_THUMBNAIL_WIDTH, 
                             PREVIEW_THUMBNAIL_HEIGHT, 
-                            PREVIEW_THUMBNAIL_FORMAT, 
+                            previewThumbnailFormat, 
                         ),
                         draggable: false,
                     }),
@@ -3221,7 +3243,8 @@ class SettingsView {
                 case "range": setting.value = parseFloat(value); break;
                 case "textarea": setting.value = value; break;
                 case "number": setting.value = parseInt(value); break;
-                default: console.warn("Unknown settings input type!");
+                case "select-one": setting.value = value; break;
+                default: console.warn(`Unknown settings input type '${type}'!`);
             }
         }
 
@@ -3253,6 +3276,7 @@ class SettingsView {
                 case "range": value = el.value; break;
                 case "textarea": value = el.value; break;
                 case "number": value = el.value; break;
+                case "select-one": value = el.value; break;
                 default: console.warn("Unknown settings input type!");
             }
             settingsData[setting] = value;
@@ -3365,6 +3389,11 @@ class SettingsView {
                 $: (el) => (settings["model-show-copy-button"] = el),
                 textContent: "Show copy button",
             }),
+            $select({
+                $: (el) => (settings["model-preview-thumbnail-type"] = el),
+                textContent: "Preview thumbnail type",
+                options: ["JPEG/WEBP", "JPEG", "WEBP"],
+            }),
             $el("h2", ["Model Add"]),
             $checkbox({
                 $: (el) => (settings["model-add-embedding-extension"] = el),