Fix: 413 Request Entity Too Large

You upload a file or post a large JSON body and get back this status, often as a bare HTML page from nginx:

413 Request Entity Too Large

Some layer between the client and your code has a maximum request body size, and your request exceeded it. Current HTTP specs (RFC 9110) call the status 413 Content Too Large; the older name is still what many servers print. Your application code may never have seen the request.

Find the layer that answered

Look at the response headers and body. A Server: nginx header with a plain HTML error page points to nginx. A JSON body or a framework error such as Express’s PayloadTooLargeError: request entity too large points to your app. A load balancer or CDN may have its own message. Fix the layer that actually responded, but remember that every layer in front of the app needs a limit at least as large.

nginx

nginx limits bodies with client_max_body_size, which defaults to 1 MB. Set it in the http, server, or location block that handles the request:

server {
    # ...
    location /api/upload {
        client_max_body_size 25m;
        proxy_pass http://127.0.0.1:3000;
    }
}

sudo nginx -t && sudo systemctl reload nginx

Express (Node.js)

The built-in body parsers default to a 100 kB limit. Raise it only where needed:

app.use(express.json({ limit: "1mb" }));
app.post("/api/import", express.json({ limit: "10mb" }), importHandler);

For file uploads, use a streaming multipart library such as multer, which has its own size options, rather than reading files into JSON.

Flask

Flask rejects bodies larger than MAX_CONTENT_LENGTH with a 413:

app.config["MAX_CONTENT_LENGTH"] = 16 * 1024 * 1024  # 16 MB

Apache, PHP, and others

• Apache httpd: LimitRequestBody.
• PHP: upload_max_filesize and post_max_size in php.ini.
• Kubernetes with the ingress-nginx controller: the nginx.ingress.kubernetes.io/proxy-body-size annotation.
• Managed load balancers and CDNs: check the provider’s documented request size limits; some cannot be raised.

Consider sending less instead

Raising limits everywhere makes it easier to exhaust memory or disk with oversized requests. Often a better fix is on the client side:

• Upload large files directly to object storage with pre-signed URLs, so they never pass through your app.
• Split big uploads into chunks, or paginate large imports.
• Compress or resize images in the browser before upload.
• Send file references instead of Base64-encoded file contents inside JSON, which inflates size by about a third.

Check the fix

head -c 2000000 /dev/zero > /tmp/test-2mb.bin
curl -s -o /dev/null -w '%{http_code}\n' \
  --data-binary @/tmp/test-2mb.bin \
  -H 'Content-Type: application/octet-stream' \
  http://localhost:8080/api/upload

A 413 means a limit is still too low; any other code means the body got through to the next layer.