diff --git a/readme.txt b/readme.txt
index 6c3762e..96d4b3f 100644
--- a/readme.txt
+++ b/readme.txt
@@ -4,7 +4,7 @@ Tags: cache, caching, performance
 Requires at least: 4.7
 Tested up to: 6.9
 Requires PHP: 7.1
-Stable tag: 1.9.0
+Stable tag: 1.9.1
 License: GPLv2 or later
 License URI: https://www.gnu.org/licenses/gpl-2.0.html
 
@@ -85,6 +85,9 @@ Create a new team account, invite a member of your team, and allow them to spin
 * Ensures debug.log files aren’t saved in a publicly-accessible location
 
 == Changelog ==
+= 1.9.1 (2026-01-07) =
+* Improvement: Add support for SpinupWP subdomains
+
 = 1.9.0 (2025-10-01) =
 * Change: Use SPINUPWP_REDIS_* variables instead of SPINUPWP_CACHE_*
 * Change: No longer enabling WP_REDIS_SELECTIVE_FLUSH by default as it can result in timeouts when flushing the cache. Flushing the object cache will now flush it for all sites on a server.
diff --git a/spinupwp.php b/spinupwp.php
index 5802ecc..4b3193f 100644
--- a/spinupwp.php
+++ b/spinupwp.php
@@ -4,7 +4,7 @@
 Plugin URI:   https://spinupwp.com
 Description:  SpinupWP helper plugin.
 Author:       SpinupWP
-Version:      1.9.0
+Version:      1.9.1
 Network:      True
 Text Domain:  spinupwp
 Requires PHP: 7.1
diff --git a/src/MagicLogin.php b/src/MagicLogin.php
index f9a8fe8..fe9b53e 100644
--- a/src/MagicLogin.php
+++ b/src/MagicLogin.php
@@ -111,6 +111,15 @@ protected function has_valid_signature( string $secret ) {
 		$url       = home_url() . "?{$query}";
 		$signature = hash_hmac( 'sha256', $url, $secret );
 
+		$subdomain = getenv( 'SPINUPWP_SUBDOMAIN' );
+		if ( $subdomain ) {
+			$subdomain_url = "https://{$subdomain}" . "?{$query}";
+			$subdomain_signature = hash_hmac( 'sha256', $subdomain_url, $secret );
+			if ( hash_equals( $subdomain_signature, $query_signature ) ) {
+				return true;
+			}
+		}
+
 		return hash_equals( $signature, $query_signature );
 	}
 
diff --git a/src/Plugin.php b/src/Plugin.php
index 8cadcf3..581d0fa 100644
--- a/src/Plugin.php
+++ b/src/Plugin.php
@@ -51,6 +51,7 @@ public function run() {
 
 			( new MagicLogin() )->init();
 			( new SiteHealth() )->init();
+			( new SubdomainUrlRewriter() )->init();
 		}
 
 		add_filter( 'spinupwp_should_use_object_cache_dropin', array( $this, 'should_use_object_cache_dropin' ) );
diff --git a/src/SubdomainUrlRewriter.php b/src/SubdomainUrlRewriter.php
new file mode 100644
index 0000000..9567c30
--- /dev/null
+++ b/src/SubdomainUrlRewriter.php
@@ -0,0 +1,93 @@
+<?php
+
+namespace SpinupWp;
+
+class SubdomainUrlRewriter {
+
+	/**
+	 * @var string
+	 */
+	private $subdomain;
+
+	/**
+	 * @var string
+	 */
+	private $site_url;
+
+	/**
+	 * Init
+	 *
+	 * @return void
+	 */
+	public function init() {
+		$this->subdomain = getenv( 'SPINUPWP_SUBDOMAIN' );
+
+		if ( ! $this->subdomain || ! $this->is_subdomain_request() ) {
+			return;
+		}
+
+		$this->site_url = home_url();
+		$this->register_hooks();
+	}
+
+	/**
+	 * Determine if the current request is via the subdomain.
+	 *
+	 * @return bool
+	 */
+	private function is_subdomain_request() {
+		return isset( $_SERVER['HTTP_HOST'] )
+			&& $_SERVER['HTTP_HOST'] === $this->subdomain;
+	}
+
+	/**
+	 * Register hooks to rewrite URLs before saving to the database.
+	 *
+	 * @return void
+	 */
+	private function register_hooks() {
+		add_filter( 'content_save_pre', array( $this, 'rewrite_urls' ) );
+		add_filter( 'excerpt_save_pre', array( $this, 'rewrite_urls' ) );
+		add_filter( 'pre_update_option', array( $this, 'rewrite_urls_recursive' ), 10, 1 );
+	}
+
+	/**
+	 * Rewrite subdomain URLs to the configured site URL.
+	 *
+	 * @param string $content
+	 *
+	 * @return string
+	 */
+	public function rewrite_urls( $content ) {
+		if ( ! is_string( $content ) || empty( $content ) ) {
+			return $content;
+		}
+
+		return str_replace(
+			array( 'https://' . $this->subdomain, 'http://' . $this->subdomain ),
+			$this->site_url,
+			$content
+		);
+	}
+
+	/**
+	 * Recursively rewrite URLs in arrays and strings.
+	 *
+	 * @param mixed $data
+	 *
+	 * @return mixed
+	 */
+	public function rewrite_urls_recursive( $data ) {
+		if ( is_string( $data ) ) {
+			return $this->rewrite_urls( $data );
+		}
+
+		if ( is_array( $data ) ) {
+			foreach ( $data as $key => $value ) {
+				$data[ $key ] = $this->rewrite_urls_recursive( $value );
+			}
+		}
+
+		return $data;
+	}
+}