diff --git a/iopaint/download.py b/iopaint/download.py
index f8fc7c9..2f7ceef 100644
--- a/iopaint/download.py
+++ b/iopaint/download.py
@@ -1,8 +1,8 @@
 import json
 import os
+from functools import lru_cache
 from typing import List
 
-from huggingface_hub.constants import HF_HUB_CACHE
 from loguru import logger
 from pathlib import Path
 
@@ -41,39 +41,119 @@ def folder_name_to_show_name(name: str) -> str:
     return name.replace("models--", "").replace("--", "/")
 
 
+@lru_cache(maxsize=512)
+def get_sd_model_type(model_abs_path: str) -> ModelType:
+    if "inpaint" in Path(model_abs_path).name.lower():
+        model_type = ModelType.DIFFUSERS_SD_INPAINT
+    else:
+        # load once to check num_in_channels
+        from diffusers import StableDiffusionInpaintPipeline
+
+        try:
+            StableDiffusionInpaintPipeline.from_single_file(
+                model_abs_path,
+                load_safety_checker=False,
+                local_files_only=True,
+                num_in_channels=9,
+            )
+            model_type = ModelType.DIFFUSERS_SD_INPAINT
+        except ValueError as e:
+            if "Trying to set a tensor of shape torch.Size([320, 4, 3, 3])" in str(e):
+                model_type = ModelType.DIFFUSERS_SD
+            else:
+                raise e
+    return model_type
+
+
+@lru_cache()
+def get_sdxl_model_type(model_abs_path: str) -> ModelType:
+    if "inpaint" in model_abs_path:
+        model_type = ModelType.DIFFUSERS_SDXL_INPAINT
+    else:
+        # load once to check num_in_channels
+        from diffusers import StableDiffusionXLInpaintPipeline
+
+        try:
+            model = StableDiffusionXLInpaintPipeline.from_single_file(
+                model_abs_path,
+                load_safety_checker=False,
+                local_files_only=True,
+                num_in_channels=9,
+            )
+            if model.unet.config.in_channels == 9:
+                # https://github.com/huggingface/diffusers/issues/6610
+                model_type = ModelType.DIFFUSERS_SDXL_INPAINT
+            else:
+                model_type = ModelType.DIFFUSERS_SDXL
+        except ValueError as e:
+            if "Trying to set a tensor of shape torch.Size([320, 4, 3, 3])" in str(e):
+                model_type = ModelType.DIFFUSERS_SDXL
+            else:
+                raise e
+    return model_type
+
+
 def scan_single_file_diffusion_models(cache_dir) -> List[ModelInfo]:
     cache_dir = Path(cache_dir)
     stable_diffusion_dir = cache_dir / "stable_diffusion"
-    stable_diffusion_xl_dir = cache_dir / "stable_diffusion_xl"
-    # logger.info(f"Scanning single file sd/sdxl models in {cache_dir}")
+    cache_file = stable_diffusion_dir / "iopaint_cache.json"
+    model_type_cache = {}
+    if cache_file.exists():
+        try:
+            with open(cache_file, "r", encoding="utf-8") as f:
+                model_type_cache = json.load(f)
+                assert isinstance(model_type_cache, dict)
+        except:
+            pass
+
     res = []
     for it in stable_diffusion_dir.glob(f"*.*"):
         if it.suffix not in [".safetensors", ".ckpt"]:
             continue
-        if "inpaint" in str(it).lower():
-            model_type = ModelType.DIFFUSERS_SD_INPAINT
-        else:
-            model_type = ModelType.DIFFUSERS_SD
+        model_abs_path = str(it.absolute())
+        model_type = model_type_cache.get(it.name)
+        if model_type is None:
+            model_type = get_sd_model_type(model_abs_path)
+        model_type_cache[it.name] = model_type
         res.append(
             ModelInfo(
                 name=it.name,
-                path=str(it.absolute()),
+                path=model_abs_path,
                 model_type=model_type,
                 is_single_file_diffusers=True,
             )
         )
+    if stable_diffusion_dir.exists():
+        with open(cache_file, "w", encoding="utf-8") as fw:
+            json.dump(model_type_cache, fw, indent=2, ensure_ascii=False)
+
+    stable_diffusion_xl_dir = cache_dir / "stable_diffusion_xl"
+    sdxl_cache_file = stable_diffusion_xl_dir / "iopaint_cache.json"
+    sdxl_model_type_cache = {}
+    if sdxl_cache_file.exists():
+        try:
+            with open(sdxl_cache_file, "r", encoding="utf-8") as f:
+                sdxl_model_type_cache = json.load(f)
+                assert isinstance(sdxl_model_type_cache, dict)
+        except:
+            pass
 
     for it in stable_diffusion_xl_dir.glob(f"*.*"):
         if it.suffix not in [".safetensors", ".ckpt"]:
             continue
-        if "inpaint" in str(it).lower():
-            model_type = ModelType.DIFFUSERS_SDXL_INPAINT
-        else:
-            model_type = ModelType.DIFFUSERS_SDXL
+        model_abs_path = str(it.absolute())
+        model_type = sdxl_model_type_cache.get(it.name)
+        if model_type is None:
+            model_type = get_sdxl_model_type(model_abs_path)
+        sdxl_model_type_cache[it.name] = model_type
+        if stable_diffusion_xl_dir.exists():
+            with open(sdxl_cache_file, "w", encoding="utf-8") as fw:
+                json.dump(sdxl_model_type_cache, fw, indent=2, ensure_ascii=False)
+
         res.append(
             ModelInfo(
                 name=it.name,
-                path=str(it.absolute()),
+                path=model_abs_path,
                 model_type=model_type,
                 is_single_file_diffusers=True,
             )
@@ -100,6 +180,8 @@ def scan_inpaint_models(model_dir: Path) -> List[ModelInfo]:
 
 
 def scan_models() -> List[ModelInfo]:
+    from huggingface_hub.constants import HF_HUB_CACHE
+
     model_dir = os.getenv("XDG_CACHE_HOME", DEFAULT_MODEL_DIR)
     available_models = []
     available_models.extend(scan_inpaint_models(model_dir))