How to Limit File Upload Size in Nginx Restricting file upload sizes is crucial for preventing denial-of-service (DoS) attacks and managing server resources. This guide explains how to configure upload limits in Nginx and Dokku deployments.

Default Nginx Configuration By default, Nginx restricts client request bodies to 1MB. This includes all POST data and file uploads.

Set Upload Limit via client_max_body_size Use the client_max_body_size directive from Nginx's ngx_http_core_module to control upload sizes. This can be configured in three contexts:

Global Configuration (Affects All Sites)

 
# /etc/nginx/nginx.conf
 
http {
...
client_max_body_size 100M;
 
}

Per-Site Configuration (Server Block)

# /etc/nginx/sites-available/default
 
server {
...
client_max_body_size 100M;
}

Location-Specific Configuration

location /uploads {
client_max_body_size 50M;
}

Apply Configuration Changes Test configuration syntax:

sudo nginx -t

Restart Nginx:

 
# Systemd systems
 
sudo systemctl restart nginx

Init systems

sudo service nginx restart

Handling Upload Limits Requests exceeding the limit receive a 413 (Request Entity Too Large) error

Browser display of this error may vary

Set client_max_body_size 0; to disable size checking

Special Configuration for Dokku For applications deployed via Dokku:

Create Nginx configuration directory:

 
mkdir -p /home/dokku/myapp/nginx.conf.d/

Create upload limit configuration:

echo 'client_max_body_size 50M;' > /home/dokku/myapp/nginx.conf.d/upload.conf

Set proper permissions:

chown dokku:dokku /home/dokku/myapp/nginx.conf.d/upload.conf

Reload Nginx:

service nginx reload

Best Practices Set limits at the most specific context needed

Always test configuration changes before applying

Monitor 413 errors in server logs

Consider application requirements when setting limits

This version features:

Clear hierarchical structure

Code blocks with syntax highlighting

Concise step-by-step instructions

Platform-specific sections (regular Nginx vs Dokku)

Important notes and best practices

Consistent command formatting

How to Limit File Upload Size in Nginx ✅

Init systems