diff --git a/README.md b/README.md
index 11fb838..c7abaab 100644
--- a/README.md
+++ b/README.md
@@ -17,3 +17,6 @@ mit folgender URL im Browser ist der Einstiegpunkt:
 
 http://127.0.0.1:8001/static/upload.html
 
+Ein Viewer für die hochgeladenen STEP files
+http://127.0.0.1:8001/static/viewer.html
+
diff --git a/main.py b/main.py
index f915f6e..bf7a54f 100644
--- a/main.py
+++ b/main.py
@@ -1,17 +1,58 @@
-from fastapi import FastAPI
+import os
+import tempfile
+import uuid
+
+from fastapi import FastAPI, UploadFile, File, HTTPException
 from fastapi.staticfiles import StaticFiles
+from fastapi.middleware.cors import CORSMiddleware
+
+from pathlib import Path
 
 
 app = FastAPI()
-
 app.mount("/static", StaticFiles(directory="static"), name="static")
 
+# Für lokales Testen mit separatem Frontend (z.B. file:// oder anderer Port)
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],   # in Produktion einschränken!
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+UPLOAD_DIR = Path("uploads")
+UPLOAD_DIR.mkdir(exist_ok=True)
+
+
 @app.get("/")
 def read_root():
     return {"Hello": "World"}
 
+@app.get("/health")
+def health():
+    return {"status": "ok"}
 
-@app.get("/items/{item_id}")
-def read_item(item_id: int, q: str | None = None):
-    return {"item_id": item_id, "q": q}
+@app.post("/upload")
+async def upload_file(file: UploadFile = File(...)):
+    filename = (file.filename or "").lower()
+    safe_name = ""
+    if not (filename.endswith(".step") or filename.endswith(".stp")):
+        raise HTTPException(status_code=400, detail="Upload a .step or .stp file")
 
+     # eindeutiger Dateiname, um Kollisionen zu vermeiden
+    suffix = Path(file.filename).suffix
+    safe_name = f"{uuid.uuid4().hex}{suffix}"
+    target = UPLOAD_DIR / safe_name
+
+    # Datei speichern (streaming)
+    with target.open("wb") as f:
+        while chunk := await file.read(1024 * 1024):
+            f.write(chunk)
+
+    return {
+        "original_filename": file.filename,
+        "stored_as": safe_name,
+        "content_type": file.content_type,
+        "size_bytes": target.stat().st_size,
+    }
diff --git a/static/upload.html b/static/upload.html
index a97cab0..29de416 100644
--- a/static/upload.html
+++ b/static/upload.html
@@ -22,7 +22,7 @@
   </div>
 
   <script>
-    const API_URL = "http://127.0.0.1:8000/upload";
+    const API_URL = "http://127.0.0.1:8001/upload";
 
     const fileInput = document.getElementById("fileInput");
     const uploadBtn = document.getElementById("uploadBtn");
diff --git a/viewer.html b/static/viewer.html
similarity index 100%
rename from viewer.html
rename to static/viewer.html