diff --git a/site/assets/js/main.js b/site/assets/js/main.js
index ab395ae..153adda 100644
--- a/site/assets/js/main.js
+++ b/site/assets/js/main.js
@@ -691,7 +691,7 @@ document.addEventListener('DOMContentLoaded', function () {
 document.addEventListener('DOMContentLoaded', function () {
     var select = document.querySelector('#joinModal select[name="membership_id"]');
     if (!select) return;
-    document.querySelectorAll('[data-target="#joinModal"][data-membership]').forEach(function (btn) {
+    document.querySelectorAll('[data-bs-target="#joinModal"][data-membership]').forEach(function (btn) {
         btn.addEventListener('click', function () { select.value = btn.getAttribute('data-membership'); });
     });
 });
diff --git a/site/includes/footer.php b/site/includes/footer.php
index 2742ed4..f982464 100644
--- a/site/includes/footer.php
+++ b/site/includes/footer.php
@@ -37,7 +37,7 @@
 
 <!-- Scripts: jQuery first (Bootstrap navbar/alerts depend on it), then plugins -->
 <?= script_tag('assets/vendor/jquery/jquery-3.7.1.min.js') ?>
-<?= script_tag('assets/vendor/bootstrap/js/bootstrap.min.js') ?>
+<?= script_tag('assets/vendor/bootstrap5/js/bootstrap.bundle.min.js') ?>
 <?= script_tag('site/assets/js/main.js') ?>
 </body>
 </html>
diff --git a/site/includes/include.php b/site/includes/include.php
index 4bd8c70..d75db93 100644
--- a/site/includes/include.php
+++ b/site/includes/include.php
@@ -58,7 +58,7 @@ $canonical = $GLOBALS['_canonical_override'] ?? match ($page) {
 <link href="https://fonts.googleapis.com/css?family=Roboto:400,500,700,900&display=swap" rel="stylesheet">
 
 <!-- Vendor: Bootstrap 4.3.1 -->
-<?= link_tag('assets/vendor/bootstrap/css/bootstrap.min.css') ?>
+<?= link_tag('assets/vendor/bootstrap5/css/bootstrap.min.css') ?>
 
 <!-- Vendor: Font Awesome 5 -->
 <?= link_tag('site/assets/fonts/fontawesome/css/all.css') ?>
diff --git a/site/includes/navbar.php b/site/includes/navbar.php
index 6152ca1..3af007f 100644
--- a/site/includes/navbar.php
+++ b/site/includes/navbar.php
@@ -14,7 +14,7 @@ $logo_dims = svg_img_dims_attr(dirname(__DIR__, 2) . '/' . $logo_rel);
       <a class="navbar-brand" href="<?= htmlspecialchars(gym_url(current_gym())) ?>">
       <img loading="eager" decoding="async" alt="Logo FitMe3070" src="<?= $logo ?>" <?= $logo_dims ?> style="width: 150px;">
     </a>
-    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation"> <span class="navbar-toggler-icon"></span> </button>
+    <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation"> <span class="navbar-toggler-icon"></span> </button>
     <div class="collapse navbar-collapse" id="navbarSupportedContent">
       <ul class="navbar-nav mx-auto ">
         <?php foreach($navbar as $key => $n):
diff --git a/site/index.php b/site/index.php
index 4016b4a..8c58137 100644
--- a/site/index.php
+++ b/site/index.php
@@ -73,7 +73,7 @@ $hero_img    = $gym['hero_image'] !== '' ? $gym['hero_image'] : 'site/assets/img
             <h1><?= htmlspecialchars($gym['hero_title'] !== '' ? $gym['hero_title'] : $gym['name']) ?><?php if ($gym['hero_subtitle'] !== ''): ?><br><span><?= htmlspecialchars($gym['hero_subtitle']) ?></span><?php endif; ?></h1>
             <div class="hero-cta-row">
                 <a href="?assunto=insc#contactos" class="site-btn">Inscreve-te Já!</a>
-                <button type="button" class="site-btn sb-ghost" data-toggle="modal" data-target="#trialModal">Marca uma Aula Experimental</button>
+                <button type="button" class="site-btn sb-ghost" data-bs-toggle="modal" data-bs-target="#trialModal">Marca uma Aula Experimental</button>
             </div>
         </div>
     </div>
@@ -496,7 +496,7 @@ if ($memberships):
                     <?php foreach ($features as $f): ?><li><i class="fas fa-check" aria-hidden="true"></i><?= htmlspecialchars($f) ?></li><?php endforeach; ?>
                 </ul>
                 <?php endif; ?>
-                <button type="button" class="site-btn pc-cta" data-toggle="modal" data-target="#joinModal"
+                <button type="button" class="site-btn pc-cta" data-bs-toggle="modal" data-bs-target="#joinModal"
                         data-membership="<?= (int) $m['id'] ?>"><?= htmlspecialchars($m['cta_label']) ?></button>
             </article>
             <?php endforeach; ?>
@@ -670,7 +670,7 @@ $session = session();
                         <?php if ($session->getFlashdata('email') !== null): ?>
                         <div class="alert alert-success alert-dismissible fade show" role="alert">
                             <?= $session->getFlashdata('email') ?>
-                            <button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">&times;</span></button>
+                            <button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="Close"></button>
                         </div>
                         <?php endif; ?>
                         <label class="consent-check">
@@ -752,12 +752,12 @@ if ($on('personal_trainer')):
         <span class="section-eyebrow">FitMe 3070</span>
         <h3 id="trialModalLabel">Marca a tua aula experimental</h3>
         <p>Treina connosco sem compromisso. Deixa os teus dados e entramos em contacto para confirmar o dia e a hora.</p>
-        <button type="button" class="trial-close" data-dismiss="modal" aria-label="Fechar">&times;</button>
+        <button type="button" class="trial-close" data-bs-dismiss="modal" aria-label="Fechar">&times;</button>
       </div>
       <form class="trial-form" method="post" action="<?= htmlspecialchars(gym_url($gym, 'agendar')) ?>">
         <?= csrf_field() ?>
         <?= public_form_trap('trial') /* honeypot + carimbo + prova de JS */ ?>
-        <div class="form-row">
+        <div class="row">
           <div class="col-12 col-md-6 mb-3">
             <input type="text" name="nome" required placeholder="Nome *" aria-label="Nome">
           </div>
@@ -796,7 +796,7 @@ if ($on('personal_trainer')):
   </div>
 </div>
 <?php if (($_GET['agendar'] ?? '') === 'erro'): ?>
-<script>document.addEventListener('DOMContentLoaded',function(){if(window.jQuery){jQuery('#trialModal').modal('show');}});</script>
+<script>document.addEventListener('DOMContentLoaded',function(){if(window.bootstrap){new bootstrap.Modal(document.getElementById('trialModal')).show();}});</script>
 <?php endif; ?>
 
 <?php
@@ -812,12 +812,12 @@ if ($memberships):
         <span class="section-eyebrow"><?= htmlspecialchars($info['name'] !== '' ? $info['name'] : APP_NAME) ?></span>
         <h3 id="joinModalLabel">Inscreve-te</h3>
         <p>Deixa os teus contactos e entramos em contacto para concluir a inscrição.</p>
-        <button type="button" class="trial-close" data-dismiss="modal" aria-label="Fechar">&times;</button>
+        <button type="button" class="trial-close" data-bs-dismiss="modal" aria-label="Fechar">&times;</button>
       </div>
       <form class="trial-form" method="post" action="<?= htmlspecialchars(gym_url($gym, 'inscricao')) ?>">
         <?= csrf_field() ?>
         <?= public_form_trap('inscricao') /* honeypot + carimbo + prova de JS */ ?>
-        <div class="form-row">
+        <div class="row">
           <div class="col-12 mb-3">
             <select name="membership_id" aria-label="Mensalidade" required>
               <?php foreach ($memberships as $m): ?>
@@ -852,7 +852,7 @@ if ($memberships):
   </div>
 </div>
 <?php if (($_GET['inscricao'] ?? '') === 'erro'): ?>
-<script>document.addEventListener('DOMContentLoaded',function(){if(window.jQuery){jQuery('#joinModal').modal('show');}});</script>
+<script>document.addEventListener('DOMContentLoaded',function(){if(window.bootstrap){new bootstrap.Modal(document.getElementById('joinModal')).show();}});</script>
 <?php endif; ?>
 <?php endif; ?>