diff --git a/.env.example b/.env.example
index d7f515c..e9457cf 100644
--- a/.env.example
+++ b/.env.example
@@ -18,6 +18,10 @@
 # Max upload file size in MB (default: 50, 0 = unlimited)
 # MAX_FILE_SIZE_MB=50
 
+# Nginx body size limit — nginx format (default: 200M, 0 = unlimited).
+# Must be >= MAX_FILE_SIZE_MB. Backend MAX_FILE_SIZE_MB is the effective arbiter.
+# NGINX_MAX_BODY_SIZE=200M
+
 # Max pages per PDF (default: 0 = unlimited). Set to 20 for HF Spaces.
 # MAX_PAGE_COUNT=0
 
diff --git a/Dockerfile b/Dockerfile
index ff3e37b..5190af8 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -24,10 +24,11 @@ FROM python:3.12-slim AS base
 ARG APP_VERSION=dev
 ENV APP_VERSION=${APP_VERSION}
 
-# System deps: poppler (pdf2image), nginx
+# System deps: poppler (pdf2image), nginx, gettext-base (envsubst for nginx template)
 RUN apt-get update && apt-get install -y --no-install-recommends \
     poppler-utils \
     nginx \
+    gettext-base \
     && rm -rf /var/lib/apt/lists/*
 
 # Python deps (common)
@@ -41,8 +42,8 @@ COPY document-parser/ .
 # Frontend static files
 COPY --from=frontend-build /build/dist /usr/share/nginx/html
 
-# Nginx config
-COPY nginx.conf /etc/nginx/sites-enabled/default
+# Nginx config (template — substituted at container start via envsubst)
+COPY nginx.conf.template /etc/nginx/sites-enabled/default.template
 
 # Non-root user
 RUN useradd --create-home --shell /bin/bash appuser
@@ -52,10 +53,11 @@ RUN mkdir -p /app/uploads /app/data && chown -R appuser:appuser /app
 
 ENV UPLOAD_DIR=/app/uploads
 ENV DB_PATH=/app/data/docling_studio.db
+ENV NGINX_MAX_BODY_SIZE=200M
 
 EXPOSE 3000
 
-CMD ["sh", "-c", "nginx && exec su appuser -c 'uvicorn main:app --host 127.0.0.1 --port 8000'"]
+CMD ["sh", "-c", "envsubst '${NGINX_MAX_BODY_SIZE}' < /etc/nginx/sites-enabled/default.template > /etc/nginx/sites-enabled/default && nginx && exec su appuser -c 'uvicorn main:app --host 127.0.0.1 --port 8000'"]
 
 # --- Remote: lightweight, delegates to Docling Serve ---
 FROM base AS remote
diff --git a/docker-compose.yml b/docker-compose.yml
index 6240ab2..d4022cf 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -117,6 +117,8 @@ services:
       context: ./frontend
     ports:
       - "3000:80"
+    environment:
+      NGINX_MAX_BODY_SIZE: ${NGINX_MAX_BODY_SIZE:-200M}
     depends_on:
       - document-parser
 
diff --git a/frontend/Dockerfile b/frontend/Dockerfile
index ea2b68a..cc8dc9e 100644
--- a/frontend/Dockerfile
+++ b/frontend/Dockerfile
@@ -9,6 +9,8 @@ RUN npm run build
 FROM nginx:alpine
 
 COPY --from=build /app/dist /usr/share/nginx/html
-COPY nginx.conf /etc/nginx/conf.d/default.conf
+COPY nginx.conf.template /etc/nginx/templates/default.conf.template
+
+ENV NGINX_MAX_BODY_SIZE=200M
 
 EXPOSE 80
diff --git a/frontend/nginx.conf b/frontend/nginx.conf.template
similarity index 92%
rename from frontend/nginx.conf
rename to frontend/nginx.conf.template
index d6b58a4..18e6e40 100644
--- a/frontend/nginx.conf
+++ b/frontend/nginx.conf.template
@@ -20,6 +20,6 @@ server {
         proxy_set_header X-Real-IP $remote_addr;
         proxy_read_timeout 900s;
         proxy_send_timeout 900s;
-        client_max_body_size 5M;
+        client_max_body_size ${NGINX_MAX_BODY_SIZE};
     }
 }
diff --git a/nginx.conf b/nginx.conf.template
similarity index 92%
rename from nginx.conf
rename to nginx.conf.template
index 20aa914..962d9d6 100644
--- a/nginx.conf
+++ b/nginx.conf.template
@@ -20,6 +20,6 @@ server {
         proxy_set_header X-Real-IP $remote_addr;
         proxy_read_timeout 900s;
         proxy_send_timeout 900s;
-        client_max_body_size 5M;
+        client_max_body_size ${NGINX_MAX_BODY_SIZE};
     }
 }