Uploading large files to a website can fail due to server-side limitations on file size. This issue is typically caused by default configurations of web servers like Nginx or Apache, or by PHP settings for sites using PHP.

This guide explains how to adjust these settings and provides detailed examples for common scenarios.

For Nginx

Nginx limits the size of client requests using the client_max_body_size directive. If this value is exceeded, Nginx will return a 413 Request Entity Too Large error.

Step-by-Step Fix

1. Locate the Nginx Configuration File

   • Default location: /etc/nginx/nginx.conf
   • For site-specific configurations: /etc/nginx/sites-available/ or /etc/nginx/conf.d/.

2. Adjust the client_max_body_size Add or modify the directive in the appropriate http, server, or location block. Examples:

   Increase upload size globally:

   http {
       client_max_body_size 100M;  # Set to 100 MB
   }
   

   Increase upload size for a specific site:

   server {
       server_name example.com;
       client_max_body_size 100M;
   }
   

   Increase upload size for a specific directory:

   location /uploads/ {
       client_max_body_size 100M;
   }
   

3. Restart Nginx Apply the changes:

   sudo systemctl restart nginx
   

4. Verify Changes

   • Upload a file to test.
   • Check logs for errors: /var/log/nginx/error.log.

For Apache

Apache restricts file uploads using the LimitRequestBody directive. If PHP is in use, it may also be restricted by post_max_size and upload_max_filesize.

Step-by-Step Fix

1. Locate the Apache Configuration File

   • Default location: /etc/httpd/conf/httpd.conf (CentOS/Red Hat) or /etc/apache2/apache2.conf (Ubuntu/Debian).
   • Virtual host configurations are often in /etc/httpd/sites-available/ or /etc/apache2/sites-available/.

2. Adjust LimitRequestBody Modify or add the directive in the <Directory> or <VirtualHost> block.

   Increase upload size globally:

   <Directory "/var/www/html">
       LimitRequestBody 104857600  # 100 MB
   </Directory>
   

   Increase upload size for a specific virtual host:

   <VirtualHost *:80>
       ServerName example.com
       DocumentRoot /var/www/example.com
       <Directory "/var/www/example.com">
           LimitRequestBody 104857600  # 100 MB
       </Directory>
   </VirtualHost>
   

3. Update PHP Settings (if applicable)

   • Edit the php.ini file (often in /etc/php.ini or /etc/php/7.x/apache2/php.ini).

   • Modify these values:

     upload_max_filesize = 100M
     post_max_size = 100M
     

   • Restart Apache to apply changes:

     sudo systemctl restart apache2  # For Ubuntu/Debian
     sudo systemctl restart httpd    # For CentOS/Red Hat
     

4. Verify Changes

   • Upload a file to test.
   • Check logs: /var/log/apache2/error.log.

Examples for Common Scenarios

1. Allow Large File Uploads to a Specific Directory (Nginx): To allow uploads up to 200 MB in a directory /var/www/uploads/:

   location /uploads/ {
       client_max_body_size 200M;
   }
   

2. Allow Large File Uploads for a Subdomain (Apache): For a subdomain uploads.example.com:

   <VirtualHost *:80>
       ServerName uploads.example.com
       DocumentRoot /var/www/uploads.example.com
       <Directory "/var/www/uploads.example.com">
           LimitRequestBody 209715200  # 200 MB
       </Directory>
   </VirtualHost>
   

3. Allow Large POST Requests (PHP Sites): Ensure PHP settings align with web server limits. For example, to allow 150 MB uploads:

   upload_max_filesize = 150M
   post_max_size = 150M
   max_execution_time = 300   # Allow enough time for the upload
   max_input_time = 300
   

4. Handling Large API Payloads (Nginx): If your API endpoint needs to handle JSON payloads up to 50 MB:

   location /api/ {
       client_max_body_size 50M;
   }
   

General Best Practices

1. Set Reasonable Limits: Avoid excessively high limits that might strain server resources.
2. Optimize Server Resources:
   • Use gzip or other compression techniques for file transfers.
   • Monitor CPU and memory usage during large uploads.
3. Secure Your Configuration:
   • Only increase limits where necessary.
   • Validate file uploads on the server-side to prevent abuse.
4. Test Thoroughly:
   • Use files of varying sizes to confirm functionality.
   • Check server logs to troubleshoot unexpected issues.