Apache's automatic 301 redirect for directory URLs without trailing slashes is actually a well-documented default behavior. When a client requests http://server/directory (without the trailing slash), Apache performs this redirect primarily for two reasons:

1. URL normalization - Ensuring consistent resource location
2. Security - Preventing relative path resolution issues

The behavior is controlled by the mod_dir module and its DirectorySlash directive. Here's what happens internally:

1. Client requests /social
2. Apache checks if /social is a directory
3. If directory and no trailing slash exists → 301 redirect to /social/
4. mod_dir then serves the directory's index file (index.html by default)

Option 1: Disable DirectorySlash (Not Recommended)

While you can disable this behavior, it's generally not advised due to security implications:

DirectorySlash Off

Security Note: This can lead to information disclosure if directory indexing is enabled, as clients could see directory contents without the trailing slash.

Option 2: RewriteRule Solution

A safer approach using mod_rewrite:

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteCond %{REQUEST_FILENAME} -d
    RewriteRule ^(.*[^/])$ $1/ [L]
</IfModule>

This internally adds the trailing slash without a 301 redirect.

Option 3: Content Negotiation Approach

For specific directories, you can use:

<Directory "/var/www/html/social">
    DirectorySlash Off
    Options +MultiViews
</Directory>

While eliminating the redirect reduces HTTP requests, consider these factors:

• Browser caching of 301 redirects is permanent
• Search engines have already indexed the redirected version
• The redirect adds minimal latency (typically <100ms)

After testing various approaches, I recommend one of these solutions:

# Preferred method for most use cases
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^(.+[^/])$ %{REQUEST_URI}/ [R=301,L]

Or for internal rewrites:

RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^(.+[^/])$ $1/ [PT,L]

Remember to clear your cache when testing these solutions. The redirect behavior might still appear if the browser has cached previous 301 responses.

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When Apache encounters a request for a directory URL without a trailing slash (e.g. /social), it automatically responds with a 301 redirect to the same URL with a trailing slash (/social/). This behavior is deeply embedded in Apache's core functionality and serves several purposes:

# Example request/response flow:
GET /directory HTTP/1.1
Host: example.com

HTTP/1.1 301 Moved Permanently
Location: http://example.com/directory/

Apache implements this redirect primarily for:

• URL canonicalization - ensuring consistent resource addressing
• Preventing duplicate content issues (SEO consideration)
• Maintaining proper relative path resolution for resources within the directory

While generally recommended to keep the redirect, you can modify this behavior using mod_dir configuration:

# In your Apache configuration or .htaccess
DirectorySlash Off

# Then explicitly handle directory requests
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^(.+[^/])$ $1/ [R=301,L]

However, this approach has caveats:

1. Relative paths in HTML documents may break
2. Directory listings (if enabled) won't work properly
3. May cause SEO issues with duplicate content

A more robust solution is to ensure your application consistently generates URLs with trailing slashes:

# PHP example forcing trailing slashes on directory URLs
function ensure_trailing_slash($url) {
    return preg_replace('/([^\/])(\?|#|$)/', '$1/$2', $url);
}

# JavaScript example
const canonicalUrl = url.endsWith('/') ? url : ${url}/;

If the double request is your primary concern, consider these optimizations:

# Cache the redirect for clients
Header always set Cache-Control "public, max-age=86400" env=REDIRECT

# Or use mod_rewrite to internally proxy (no client redirect)
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^(.*[^/])$ $1/ [PT]

Here's a complete .htaccess solution that maintains SEO benefits while minimizing redirects:

<IfModule mod_rewrite.c>
    RewriteEngine On
    
    # Handle directory requests without slash
    RewriteCond %{REQUEST_FILENAME} -d
    RewriteRule ^(.*[^/])$ /$1/ [R=301,L]
    
    # Standard front controller pattern
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)$ index.php [QSA,L]
</IfModule>

<IfModule mod_headers.c>
    Header set Cache-Control "max-age=86400, public" env=REDIRECT
</IfModule>