DevOps

    Resolving "413 Request Entity Too Large" Error in NGINX During Image Upload


    Objective

    To address and resolve the issue where image uploads to an application via NGINX reverse proxy result in the error:

    "413 Request Entity Too Large"

    Root Cause

    This error typically occurs when the size of the request body (e.g., an uploaded file or image) exceeds the limits configured in NGINX or the backend server.

    Resolution Steps

    1. NGINX Configuration

    Ensure the following directives are included within the appropriate server or location block in your NGINX configuration file:

    location / {    proxy_pass http://localhost:9002;    proxy_set_header Host $host;    proxy_set_header X-Real-IP $remote_addr;    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;    proxy_buffer_size 128k;           # Buffer size for response headers    proxy_buffers 4 256k;             # Number and size of buffers    proxy_busy_buffers_size 256k;     # Busy buffer size    client_max_body_size 10m;        # Maximum client request body size} 

    Explanation of Options:

    • proxy_pass: Forwards requests to the backend server.

    • proxy_set_header: Ensures original headers and IPs are passed to the backend.

    • proxy_buffer_size: Avoids header overflow.

    • proxy_buffers: Defines the number and size of temporary buffers for the response body.

    • proxy_busy_buffers_size: Used during data streaming to the client.

    • client_max_body_size: Sets max upload size allowed by NGINX.

    Note: client_max_body_size must be placed inside server {} or location {} block—not just globally.

    2. Restart/Reload NGINX

    Validate and apply the changes:

    sudo nginx -tsudo systemctl reload nginx 

    Verification

    • Upload an image smaller than 10MB.

    • Confirm that the upload is successful without encountering HTTP 413 errors.

    Conclusion

    By setting client_max_body_size and aligning buffer limits with the backend application limits, the issue of image uploads failing due to size constraints in NGINX can be effectively resolved.

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