Fix: Nginx 413 Request Entity Too Large

!Symptoms

• File uploads fail with '413 Request Entity Too Large'
• POST requests with large bodies are rejected
• Only large files fail, small files work fine

?Root Causes

• Nginx client_max_body_size is set too low (default is 1MB)
• Multiple Nginx config levels overriding each other (http, server, location)
• Reverse proxy or CDN in front of Nginx also has a body size limit
• Application framework has its own body size limit (Express, PHP, etc.)

#Diagnosis Steps

1. 1Check Nginx config for client_max_body_size: `nginx -T | grep client_max_body_size`
2. 2Determine the size of the failing request body
3. 3Check all config levels (http, server, location) for conflicting settings
4. 4Check if a CDN (CloudFlare, etc.) is also limiting: CloudFlare free plan limits to 100MB

>Fix

1. 1Set client_max_body_size in Nginx config: `client_max_body_size 50m;` in the appropriate block
2. 2Add it at the server or location level, not just http level
3. 3Reload Nginx: `nginx -t && systemctl reload nginx`
4. 4Also increase application-level limits (e.g., PHP upload_max_filesize, Node bodyParser limit)
5. 5If behind CDN, increase upload limit there too

*Prevention

• Set client_max_body_size explicitly in all server blocks that handle uploads
• Document maximum upload sizes in API documentation
• Implement client-side file size validation before upload
• Use multipart/chunked uploads for very large files
• Test file upload limits as part of deployment verification

Related Error Messages