Multisite: Redirecting Subsites’ Login URLs to the Main Site

A WordPress Multisite network enables you to manage multiple websites under a single WordPress installation. By default, each subsite in a Multisite setup has its own login URL, typically located at https://subsite.domain.com/wp-login.php. However, for centralized user management or branding purposes, you may want all login attempts across subsites to redirect to the main site’s login URL.

This article provides a step-by-step guide to implementing this redirection.

Why Redirect Login URLs in a Multisite Setup?

1. Centralized Authentication:
   • A single login page for all subsites simplifies user management and avoids confusion among users.
2. Improved Security:
   • By reducing the number of accessible login endpoints, you lower the risk of brute force attacks.
3. Consistent User Experience:
   • Branding and design on the main login page can create a cohesive experience for users.

Implementation Steps

1. Use wp_redirect in a Custom Plugin or Theme

To redirect all login requests from subsites to the main site’s login page, add the following code to your Multisite network:

add_action('login_form', 'redirect_subsite_login_to_main');

function redirect_subsite_login_to_main() {
    $main_site_login_url = network_home_url('wp-login.php');
    $current_site_id = get_current_blog_id();
    $main_site_id = 1; // The ID of your main site (usually 1)

    if ($current_site_id !== $main_site_id) {
        wp_redirect($main_site_login_url);
        exit;
    }
}

How it Works:

• The login_form hook triggers whenever the login page is loaded.
• The function checks whether the current site is the main site.
• If it’s a subsite, the user is redirected to the main site’s login page.

2. Modify the .htaccess File

If you’d prefer a server-side solution, you can edit the .htaccess file to perform the redirection.

Add the following snippet:

RewriteEngine On
RewriteCond %{REQUEST_URI} ^/wp-login\.php$ [NC]
RewriteCond %{HTTP_HOST} !^mainsite\.domain\.com$ [NC]
RewriteRule ^(.*)$ https://mainsite.domain.com/wp-login.php [R=301,L]

How it Works:

• Checks if the requested URL is wp-login.php.
• Ensures the request is not for the main site.
• Redirects users to the main site’s login page.

Note: Always back up your .htaccess file before making changes.

3. Using a Multisite-Compatible Plugin

For non-developers, plugins like “WP Multisite Login Redirect” can automate this process:

1. Install and activate the plugin across your network.
2. Configure the main login URL in the plugin settings.
3. The plugin will handle redirections for all subsites.

Testing the Redirection

1. Attempt to visit the login URL of a subsite, e.g., https://subsite.domain.com/wp-login.php.
2. Ensure the browser redirects to https://mainsite.domain.com/wp-login.php.

Potential Issues

1. Infinite Redirect Loops:
   • If improperly configured, users might get stuck in a loop. Double-check the logic in your PHP or .htaccess file.
2. Custom Login Pages:
   • If subsites have custom login pages, consider excluding those pages from redirection.
3. Plugin Conflicts:
   • Ensure no active plugins interfere with login URL modifications.

Conclusion

Redirecting all subsites’ login URLs to the main site’s login page is a straightforward way to streamline user authentication and enhance security in a WordPress Multisite. Whether through PHP, server configurations, or plugins, you can choose the method that best suits your technical skills and project requirements.

For more advanced customization or troubleshooting, consult the WordPress Codex or hire a professional WordPress developer. Let us know in the comments if you have questions!