```html

When configuring Nginx to serve individual static files like robots.txt, favicon.ico, or sitemap.xml, both root and alias directives can achieve similar results - but with crucial technical distinctions:

# Using alias (exact file path)
location /robots.txt {
    alias /home/www/static/robots.txt;
    expires 1d;
}

# Using root (directory path)
location /robots.txt {
    root /home/www/static;
    expires 1d;
}

Path Resolution:

• alias completely replaces the matched path segment (/robots.txt) with the specified file path
• root appends the full request URI to the directory path

Common Pitfall Example:

# INCORRECT alias usage (double path)
location /static/ {
    alias /home/www/static/;  # Will try to serve from /home/www/static/static/
}

# CORRECTED version
location /static/ {
    alias /home/www/static/;
}

The alias directive requires careful path specification to prevent directory traversal vulnerabilities:

# Secure configuration for alias
location ~ ^/(robots\.txt|favicon\.ico)$ {
    alias /home/www/secure_static/$1;
    add_header X-Content-Type-Options "nosniff";
}

For high-traffic scenarios, consider this optimized setup:

location = /robots.txt {
    root /home/www/static;
    open_file_cache max=1000 inactive=20s;
    open_file_cache_valid 30s;
    open_file_cache_min_uses 2;
    open_file_cache_errors on;
}

Use alias when:

• Serving files outside the default document root
• Mapping URLs to completely different filesystem paths
• Need precise control over the exact file location

Use root when:

• Files are within the standard directory structure
• Maintaining consistent path relationships
• Working with location blocks that match directory patterns

For complex static file handling with cache control:

location ~* ^/(robots\.txt|humans\.txt|crossdomain\.xml)$ {
    alias /home/www/domain_configs/$1;
    access_log off;
    log_not_found off;
    expires max;
    add_header Cache-Control "public";
    etag on;
}

---

While both directives can serve static files, their path resolution differs fundamentally:

# alias - replaces the matched URI segment with specified path
location /robots.txt {
    alias /home/www/static/robots.txt; # full file path required
}

# root - prepends the specified path to the URI
location /robots.txt {
    root /home/www/static; # directory path only (trailing slash optional)
}

Directory traversal risks: alias may expose parent directories if misconfigured:

# UNSAFE configuration example:
location /static/ {
    alias /home/www/static/;
}
# Requests to /static/../ would traverse outside web root

root is generally safer as it anchors paths within the specified directory.

Both directives perform similarly for single files, but alias shows advantages when:

• Serving files from multiple non-standard locations
• Mapping complex URL structures to filesystem paths

For single files:

# Recommended approach for robots.txt/humans.txt/favicon.ico
location = /robots.txt {
    root /home/www/static;
    expires 24h;
    add_header Cache-Control public;
}

For directory mappings:

# Preferred method for directory serving
location /assets/ {
    root /home/www/static;
    # Additional directives...
}

Permission problems: Ensure Nginx worker process has read access:

sudo chown -R www-data:www-data /home/www/static
sudo chmod -R 755 /home/www/static

Cache headaches: Always test with curl to bypass browser caching:

curl -I http://yoursite.com/robots.txt

For serving individual static files like robots.txt:

• Use root when files reside in standard locations
• Prefer alias only when needing non-standard path mapping
• Always include the = modifier for exact matching