diff --git a/app/app.py b/app/app.py
index 27e31a6..52e95ea 100644
--- a/app/app.py
+++ b/app/app.py
@@ -191,9 +191,29 @@ def register_context_processors(app):
     @app.context_processor
     def inject_config():
         """Inject configuration variables into all templates"""
+        # Cache-busting token for the uploadable logos.
+        #
+        # Must be appended OUTSIDE url_for(): passing 'logo.png?v=1' as the
+        # filename makes Flask percent-encode the '?' into '%3F', which asks
+        # for a file literally named "logo.png%3Fv=1" and 404s.
+        #
+        # Derived from the newest logo's mtime so that uploading a new logo in
+        # Admin → Customize Logos is picked up immediately, rather than reusing
+        # a hardcoded value the browser has already cached.
+        logo_version = 1
+        for _logo_name in ('header_logo.png', 'login_logo.png'):
+            try:
+                _mtime = int(os.path.getmtime(
+                    os.path.join(app.config['UPLOAD_FOLDER'], _logo_name)))
+                logo_version = max(logo_version, _mtime)
+            except OSError:
+                # Logo not uploaded yet — keep the current token.
+                pass
+
         return {
             'server_version': app.config['SERVER_VERSION'],
             'build_date': app.config['BUILD_DATE'],
+            'logo_version': logo_version,
             'logo_exists': os.path.exists(
                 os.path.join(app.root_path, app.config['UPLOAD_FOLDERLOGO'], 'logo.png')
             )
diff --git a/app/templates/auth/login.html b/app/templates/auth/login.html
index 5d4a88d..ff9fcb0 100644
--- a/app/templates/auth/login.html
+++ b/app/templates/auth/login.html
@@ -181,7 +181,7 @@
     <div class="login-container">
         <!-- Logo Section (Left - 2/3) -->
         <div class="logo-section">
-            <img src="{{ url_for('static', filename='uploads/login_logo.png') }}?v={{ range(1, 999999) | random }}" 
+            <img src="{{ url_for('static', filename='uploads/login_logo.png') }}?v={{ logo_version }}" 
                  alt="DigiServer Logo" 
                  onerror="this.style.display='none';">
         </div>
diff --git a/app/templates/base.html b/app/templates/base.html
index f9a7d30..a242638 100644
--- a/app/templates/base.html
+++ b/app/templates/base.html
@@ -376,7 +376,7 @@
     <header>
         <div class="container">
             <h1>
-                <img src="{{ url_for('static', filename='uploads/header_logo.png?v=1') }}" alt="DigiServer" style="height: 32px; width: auto; margin-right: 8px;" onerror="this.style.display='none';" onload="this.style.display='inline';">
+                <img src="{{ url_for('static', filename='uploads/header_logo.png') }}?v={{ logo_version }}" alt="DigiServer" style="height: 32px; width: auto; margin-right: 8px;" onerror="this.style.display='none';" onload="this.style.display='inline';">
                 DigiServer
             </h1>
             <nav>