When configuring Nginx, you might need to handle URLs that start with a specific numeric pattern. A common requirement is matching URLs where the first 5 characters are digits, like:

site.com/12345/
site.com/12345

Many developers try these patterns unsuccessfully:

location ^/([0-9]) { }
location ^/(\\d\\d\\d\\d\\d) {}
location /(\\d\\d\\d\\d\\d) {}

The issues with these attempts include:

• Missing the quantifier for 5 digits
• Incorrect use of regex anchors
• Improper escaping in Nginx location syntax

Here's the proper way to match 5-digit prefixes:

location ~ ^/[0-9]{5}(/|$) {
    # Your configuration here
    # Example: proxy_pass or root directive
}

This regex pattern works because:

• ~ enables regex matching
• ^ anchors to start of URI
• [0-9]{5} matches exactly 5 digits
• (/|$) matches either a trailing slash or end of string

Here's a complete Nginx configuration snippet:

server {
    listen 80;
    server_name site.com;
    
    location ~ ^/[0-9]{5}(/|$) {
        root /var/www/numeric_ids;
        try_files $uri $uri/ =404;
    }
    
    # Other location blocks...
}

For more complex scenarios:

# Match 5 digits followed by specific path
location ~ ^/[0-9]{5}/products {
    # Configuration for product pages
}

# Capture the digits for later use
location ~ ^/([0-9]{5})(/|$) {
    set $user_id $1;
    # Use $user_id in your configuration
}

Remember that regex locations have higher overhead than prefix matches. For high-traffic sites, consider:

• Using exact matches (=) when possible
• Placing regex locations after static ones
• Testing with nginx -T to validate syntax

When working with Nginx configuration, a common requirement is to match URLs that begin with specific patterns. In this case, we need to match URLs where the first path segment contains exactly 5 digits, like:

site.com/12345/
site.com/12345

Many developers try these common patterns first, but they don't work in Nginx location blocks:

location ^/([0-9]) { }  # Too broad, matches any single digit
location ^/(\\d\\d\\d\\d\\d) {}  # Wrong syntax for Nginx
location /(\\d\\d\\d\\d\\d) {}  # Missing proper anchors

Nginx uses a modified regex syntax for location blocks. The correct solution requires:

location ~ ^/[0-9]{5}(/|$) {
    # Your configuration here
}

Breaking this down:

• ~ enables regex matching
• ^ anchors to start of URL path
• /[0-9]{5} matches exactly 5 digits after initial slash
• (/|$) matches either trailing slash or end of string

Here's a full configuration example that routes 5-digit paths to a specific handler:

server {
    listen 80;
    server_name site.com;

    # Match 5-digit URLs
    location ~ ^/[0-9]{5}(/|$) {
        proxy_pass http://backend_service;
        proxy_set_header Host $host;
    }

    # Other locations...
}

After making changes, always test your configuration:

nginx -t  # Test configuration syntax
nginx -s reload  # Reload configuration

For high-traffic sites, consider these optimizations:

# Prefix match first, then regex
location / {
    try_files $uri @numeric_check;
}

location @numeric_check {
    if ($uri ~ "^/[0-9]{5}(/|$)") {
        proxy_pass http://backend_service;
    }
}