diff --git a/app.py b/app.py
index 807be11..cc962ca 100644
--- a/app.py
+++ b/app.py
@@ -4,7 +4,7 @@ Simple Tablet Lending and Return Management Web Application
 with SQLite backend
 """
 
-from flask import Flask, render_template, request, redirect, url_for, flash
+from flask import Flask, render_template, request, redirect, url_for, flash, make_response, session
 import sqlite3
 import os
 from datetime import datetime
@@ -25,15 +25,41 @@ app.config['BABEL_TRANSLATION_DIRECTORIES'] = 'translations'
 
 # Locale selector function
 def get_locale():
-    # Try to get language from URL parameter
-    lang = request.args.get('lang')
+    # Try to get language from cookie
+    lang = request.cookies.get('language')
     if lang and lang in app.config['LANGUAGES']:
         return lang
     # Try to get from session
     if hasattr(request, 'session') and 'language' in request.session:
         return request.session['language']
-    # Try to get from browser preferences
-    return request.accept_languages.best_match(app.config['LANGUAGES'].keys())
+    # Default to Spanish (es) for internal app
+    return 'es'
+
+
+# Before request handler to set language from URL param and persist to cookie/session
+@app.before_request
+def handle_language():
+    lang = request.args.get('lang')
+    if lang and lang in app.config['LANGUAGES']:
+        # Store in session
+        session['language'] = lang
+        # Set cookie for longer persistence (1 year)
+        # Note: We need to use response.set_cookie, but before_request can't modify response
+        # So we'll handle this in a separate route
+    return None
+
+
+# Language switcher endpoint
+@app.route('/set_language')
+def set_language():
+    lang = request.args.get('lang')
+    if lang and lang in app.config['LANGUAGES']:
+        session['language'] = lang
+        # Set cookie
+        resp = make_response(redirect(request.referrer or '/'))
+        resp.set_cookie('language', lang, max_age=31536000)  # 1 year
+        return resp
+    return redirect(request.referrer or '/')
 
 # Initialize Babel with locale selector
 babel = Babel(app, locale_selector=get_locale)
diff --git a/templates/add_non_loanable_device.html b/templates/add_non_loanable_device.html
index ae0489e..52ec344 100644
--- a/templates/add_non_loanable_device.html
+++ b/templates/add_non_loanable_device.html
@@ -1,63 +1,63 @@
 {% extends "base.html" %}
 
 {% block content %}
-    <h2>Add Non-Loanable Device</h2>
-    <p>Add a device that will be tracked in inventory but cannot be loaned to users (e.g., projectors, monitors, etc.)</p>
+    <h2>{{ _('Add Non-Loanable Device') }}</h2>
+    <p>{{ _('Add a device that will be tracked in inventory but cannot be loaned to users (e.g., projectors, monitors, etc.)') }}</p>
     
     <form method="POST" action="/add_non_loanable_device">
         <div class="form-group">
-            <label for="device_type">Device Type:</label>
+            <label for="device_type">{{ _('Device Type') }}:</label>
             <select id="device_type" name="device_type" required>
-                <option value="">Select device type...</option>
-                <option value="projector">Projector</option>
-                <option value="monitor">Monitor</option>
-                <option value="laptop">Laptop (non-loanable)</option>
-                <option value="printer">Printer</option>
-                <option value="camera">Camera</option>
-                <option value="audio">Audio Equipment</option>
-                <option value="network">Network Equipment</option>
-                <option value="other">Other</option>
+                <option value="">{{ _('Select device type...') }}</option>
+                <option value="projector">{{ _('Projector') }}</option>
+                <option value="monitor">{{ _('Monitor') }}</option>
+                <option value="laptop">{{ _('Laptop (non-loanable)') }}</option>
+                <option value="printer">{{ _('Printer') }}</option>
+                <option value="camera">{{ _('Camera') }}</option>
+                <option value="audio">{{ _('Audio Equipment') }}</option>
+                <option value="network">{{ _('Network Equipment') }}</option>
+                <option value="other">{{ _('Other') }}</option>
             </select>
         </div>
 
         <div class="form-group">
-            <label for="brand">Brand:</label>
+            <label for="brand">{{ _('Brand') }}:</label>
             <input type="text" id="brand" name="brand" required>
         </div>
 
         <div class="form-group">
-            <label for="model">Model:</label>
+            <label for="model">{{ _('Model') }}:</label>
             <input type="text" id="model" name="model" required>
         </div>
 
         <div class="form-group">
-            <label for="serial_number">Serial Number:</label>
+            <label for="serial_number">{{ _('Serial Number') }}:</label>
             <input type="text" id="serial_number" name="serial_number" required>
         </div>
 
         <div class="form-group">
-            <label for="location">Location:</label>
+            <label for="location">{{ _('Location') }}:</label>
             <input type="text" id="location" name="location">
         </div>
 
         <div class="form-group">
-            <label for="purchase_date">Purchase Date:</label>
+            <label for="purchase_date">{{ _('Purchase Date') }}:</label>
             <input type="date" id="purchase_date" name="purchase_date">
         </div>
 
         <div class="form-group">
-            <label for="purchase_cost">Purchase Cost:</label>
+            <label for="purchase_cost">{{ _('Purchase Cost') }}:</label>
             <input type="number" id="purchase_cost" name="purchase_cost" step="0.01">
         </div>
 
         <div class="form-group">
-            <label for="notes">Notes:</label>
+            <label for="notes">{{ _('Notes') }}:</label>
             <textarea id="notes" name="notes"></textarea>
         </div>
 
         <div class="form-group">
-            <button type="submit" class="btn">Add Device</button>
-            <a href="/non_loanable_devices" class="btn">Cancel</a>
+            <button type="submit" class="btn">{{ _('Add Device') }}</button>
+            <a href="/non_loanable_devices" class="btn">{{ _('Cancel') }}</a>
         </div>
     </form>
 {% endblock %}
diff --git a/templates/add_tablet.html b/templates/add_tablet.html
index 8199daf..bc1fa4b 100644
--- a/templates/add_tablet.html
+++ b/templates/add_tablet.html
@@ -1,30 +1,30 @@
 {% extends "base.html" %}
 
 {% block content %}
-    <h2>Add New Tablet</h2>
+    <h2>{{ _('Add New Tablet') }}</h2>
     <form method="POST" action="/add_tablet">
         <div class="form-group">
-            <label for="brand">Brand:</label>
+            <label for="brand">{{ _('Brand') }}:</label>
             <input type="text" id="brand" name="brand" required>
         </div>
 
         <div class="form-group">
-            <label for="model">Model:</label>
+            <label for="model">{{ _('Model') }}:</label>
             <input type="text" id="model" name="model" required>
         </div>
 
         <div class="form-group">
-            <label for="serial_number">Serial Number:</label>
+            <label for="serial_number">{{ _('Serial Number') }}:</label>
             <input type="text" id="serial_number" name="serial_number" required>
         </div>
 
         <div class="form-group">
-            <label for="notes">Notes:</label>
+            <label for="notes">{{ _('Notes') }}:</label>
             <textarea id="notes" name="notes"></textarea>
         </div>
 
         <div class="form-group">
-            <button type="submit" class="btn">Add Tablet</button>
+            <button type="submit" class="btn">{{ _('Add Tablet') }}</button>
         </div>
     </form>
-{% endblock %}
\ No newline at end of file
+{% endblock %}
diff --git a/templates/add_user.html b/templates/add_user.html
index 2bcd10b..78439d9 100644
--- a/templates/add_user.html
+++ b/templates/add_user.html
@@ -1,30 +1,30 @@
 {% extends "base.html" %}
 
 {% block content %}
-    <h2>Add New User</h2>
+    <h2>{{ _('Add New User') }}</h2>
     <form method="POST" action="/add_user">
         <div class="form-group">
-            <label for="name">Name:</label>
+            <label for="name">{{ _('Name') }}:</label>
             <input type="text" id="name" name="name" required>
         </div>
 
         <div class="form-group">
-            <label for="email">Email:</label>
+            <label for="email">{{ _('Email') }}:</label>
             <input type="email" id="email" name="email">
         </div>
 
         <div class="form-group">
-            <label for="phone">Phone:</label>
+            <label for="phone">{{ _('Phone') }}:</label>
             <input type="text" id="phone" name="phone">
         </div>
 
         <div class="form-group">
-            <label for="identification">Identification:</label>
+            <label for="identification">{{ _('Identification') }}:</label>
             <input type="text" id="identification" name="identification" required>
         </div>
 
         <div class="form-group">
-            <button type="submit" class="btn">Add User</button>
+            <button type="submit" class="btn">{{ _('Add User') }}</button>
         </div>
     </form>
-{% endblock %}
\ No newline at end of file
+{% endblock %}
diff --git a/templates/base.html b/templates/base.html
index de6ba8f..50ff3ff 100644
--- a/templates/base.html
+++ b/templates/base.html
@@ -122,7 +122,7 @@
                         <span class="text-sm opacity-80">{{ _('Language') }}:</span>
                         {% for lang_code, lang_name in config['LANGUAGES'].items() %}
                             <a 
-                                href="?lang={{ lang_code }}"
+                                href="{{ url_for('set_language', lang=lang_code) }}"
                                 class="px-2 py-1 text-sm rounded hover:bg-white/20 transition-colors
                                        {% if language == lang_code %}bg-white/30 font-medium{% endif %}"
                             >
diff --git a/templates/edit_non_loanable_device.html b/templates/edit_non_loanable_device.html
index 80c90b4..339a252 100644
--- a/templates/edit_non_loanable_device.html
+++ b/templates/edit_non_loanable_device.html
@@ -1,71 +1,71 @@
 {% extends "base.html" %}
 
 {% block content %}
-    <h2>Edit Non-Loanable Device</h2>
+    <h2>{{ _('Edit Non-Loanable Device') }}</h2>
     
     <form method="POST" action="/edit_non_loanable_device/{{ device.id }}">
         <div class="form-group">
-            <label for="device_type">Device Type:</label>
+            <label for="device_type">{{ _('Device Type') }}:</label>
             <select id="device_type" name="device_type" required>
-                <option value="projector" {% if device.device_type == 'projector' %}selected{% endif %}>Projector</option>
-                <option value="monitor" {% if device.device_type == 'monitor' %}selected{% endif %}>Monitor</option>
-                <option value="laptop" {% if device.device_type == 'laptop' %}selected{% endif %}>Laptop (non-loanable)</option>
-                <option value="printer" {% if device.device_type == 'printer' %}selected{% endif %}>Printer</option>
-                <option value="camera" {% if device.device_type == 'camera' %}selected{% endif %}>Camera</option>
-                <option value="audio" {% if device.device_type == 'audio' %}selected{% endif %}>Audio Equipment</option>
-                <option value="network" {% if device.device_type == 'network' %}selected{% endif %}>Network Equipment</option>
-                <option value="other" {% if device.device_type == 'other' %}selected{% endif %}>Other</option>
+                <option value="projector" {% if device.device_type == 'projector' %}selected{% endif %}>{{ _('Projector') }}</option>
+                <option value="monitor" {% if device.device_type == 'monitor' %}selected{% endif %}>{{ _('Monitor') }}</option>
+                <option value="laptop" {% if device.device_type == 'laptop' %}selected{% endif %}>{{ _('Laptop (non-loanable)') }}</option>
+                <option value="printer" {% if device.device_type == 'printer' %}selected{% endif %}>{{ _('Printer') }}</option>
+                <option value="camera" {% if device.device_type == 'camera' %}selected{% endif %}>{{ _('Camera') }}</option>
+                <option value="audio" {% if device.device_type == 'audio' %}selected{% endif %}>{{ _('Audio Equipment') }}</option>
+                <option value="network" {% if device.device_type == 'network' %}selected{% endif %}>{{ _('Network Equipment') }}</option>
+                <option value="other" {% if device.device_type == 'other' %}selected{% endif %}>{{ _('Other') }}</option>
             </select>
         </div>
 
         <div class="form-group">
-            <label for="brand">Brand:</label>
+            <label for="brand">{{ _('Brand') }}:</label>
             <input type="text" id="brand" name="brand" value="{{ device.brand }}" required>
         </div>
 
         <div class="form-group">
-            <label for="model">Model:</label>
+            <label for="model">{{ _('Model') }}:</label>
             <input type="text" id="model" name="model" value="{{ device.model }}" required>
         </div>
 
         <div class="form-group">
-            <label for="serial_number">Serial Number:</label>
+            <label for="serial_number">{{ _('Serial Number') }}:</label>
             <input type="text" id="serial_number" name="serial_number" value="{{ device.serial_number }}" required>
         </div>
 
         <div class="form-group">
-            <label for="location">Location:</label>
+            <label for="location">{{ _('Location') }}:</label>
             <input type="text" id="location" name="location" value="{{ device.location or '' }}">
         </div>
 
         <div class="form-group">
-            <label for="status">Status:</label>
+            <label for="status">{{ _('Status') }}:</label>
             <select id="status" name="status" required>
-                <option value="available" {% if device.status == 'available' %}selected{% endif %}>Available</option>
-                <option value="in_use" {% if device.status == 'in_use' %}selected{% endif %}>In Use</option>
-                <option value="maintenance" {% if device.status == 'maintenance' %}selected{% endif %}>Maintenance</option>
-                <option value="retired" {% if device.status == 'retired' %}selected{% endif %}>Retired</option>
+                <option value="available" {% if device.status == 'available' %}selected{% endif %}>{{ _('Available') }}</option>
+                <option value="in_use" {% if device.status == 'in_use' %}selected{% endif %}>{{ _('In Use') }}</option>
+                <option value="maintenance" {% if device.status == 'maintenance' %}selected{% endif %}>{{ _('Maintenance') }}</option>
+                <option value="retired" {% if device.status == 'retired' %}selected{% endif %}>{{ _('Retired') }}</option>
             </select>
         </div>
 
         <div class="form-group">
-            <label for="purchase_date">Purchase Date:</label>
+            <label for="purchase_date">{{ _('Purchase Date') }}:</label>
             <input type="date" id="purchase_date" name="purchase_date" value="{{ device.purchase_date or '' }}">
         </div>
 
         <div class="form-group">
-            <label for="purchase_cost">Purchase Cost:</label>
+            <label for="purchase_cost">{{ _('Purchase Cost') }}:</label>
             <input type="number" id="purchase_cost" name="purchase_cost" step="0.01" value="{{ device.purchase_cost or '' }}">
         </div>
 
         <div class="form-group">
-            <label for="notes">Notes:</label>
+            <label for="notes">{{ _('Notes') }}:</label>
             <textarea id="notes" name="notes">{{ device.notes or '' }}</textarea>
         </div>
 
         <div class="form-group">
-            <button type="submit" class="btn">Update Device</button>
-            <a href="/non_loanable_devices" class="btn">Cancel</a>
+            <button type="submit" class="btn">{{ _('Update Device') }}</button>
+            <a href="/non_loanable_devices" class="btn">{{ _('Cancel') }}</a>
         </div>
     </form>
 {% endblock %}
diff --git a/templates/history.html b/templates/history.html
index 061ffbd..b5018e9 100644
--- a/templates/history.html
+++ b/templates/history.html
@@ -2,18 +2,18 @@
 
 {% block content %}
     <div class="section">
-        <h2>Loan History</h2>
+        <h2>{{ _('Loan History') }}</h2>
         {% if loans %}
             <div class="table-container">
                 <table>
                     <thead>
                         <tr>
-                            <th>Tablet</th>
-                            <th>Serial Number</th>
-                            <th>Borrower</th>
-                            <th>Loan Date</th>
-                            <th>Return Date</th>
-                            <th>Status</th>
+                            <th>{{ _('Tablet') }}</th>
+                            <th>{{ _('Serial Number') }}</th>
+                            <th>{{ _('Borrower') }}</th>
+                            <th>{{ _('Loan Date') }}</th>
+                            <th>{{ _('Return Date') }}</th>
+                            <th>{{ _('Status') }}</th>
                         </tr>
                     </thead>
                     <tbody>
@@ -31,7 +31,7 @@
                 </table>
             </div>
         {% else %}
-            <p>No loan history available.</p>
+            <p>{{ _('No loan history available.') }}</p>
         {% endif %}
     </div>
-{% endblock %}
\ No newline at end of file
+{% endblock %}
diff --git a/templates/loan_tablet.html b/templates/loan_tablet.html
index b9f2527..ce13733 100644
--- a/templates/loan_tablet.html
+++ b/templates/loan_tablet.html
@@ -1,16 +1,16 @@
 {% extends "base.html" %}
 
 {% block content %}
-    <h2>Loan Tablet</h2>
+    <h2>{{ _('Loan Tablet') }}</h2>
     <form method="POST" action="/loan_tablet">
         <!-- Tablet Selection with Search -->
         <div class="form-group">
-            <label for="tablet_id">Tablet:</label>
+            <label for="tablet_id">{{ _('Tablet') }}:</label>
             <input type="text" id="tablet_search" class="search-input"
-                   placeholder="Search tablets (brand, model, or serial)..."
+                   placeholder="{{ _('Search tablets (brand, model, or serial)...') }}"
                    onkeyup="filterDropdown('tablet_search', 'tablet_id')">
             <select id="tablet_id" name="tablet_id" required size="5">
-                <option value="">Select a tablet</option>
+                <option value="">{{ _('Select a tablet') }}</option>
                 {% for tablet in available_tablets %}
                     <option value="{{ tablet.id }}"
                             data-search="{{ tablet.brand|lower }} {{ tablet.model|lower }} {{ tablet.serial_number|lower }}">
@@ -22,12 +22,12 @@
 
         <!-- User Selection with Search -->
         <div class="form-group">
-            <label for="user_id">User:</label>
+            <label for="user_id">{{ _('User') }}:</label>
             <input type="text" id="user_search" class="search-input"
-                   placeholder="Search users (name or ID)..."
+                   placeholder="{{ _('Search users (name or ID)...') }}"
                    onkeyup="filterDropdown('user_search', 'user_id')">
             <select id="user_id" name="user_id" required size="5">
-                <option value="">Select a user</option>
+                <option value="">{{ _('Select a user') }}</option>
                 {% for user in users %}
                     <option value="{{ user.id }}"
                             data-search="{{ user.name|lower }} {{ user.identification|lower }}">
@@ -38,7 +38,7 @@
         </div>
 
         <div class="form-group">
-            <button type="submit" class="btn">Loan Tablet</button>
+            <button type="submit" class="btn">{{ _('Loan Tablet') }}</button>
         </div>
     </form>
 
@@ -75,4 +75,4 @@
             overflow-y: auto;
         }
     </style>
-{% endblock %}
\ No newline at end of file
+{% endblock %}
diff --git a/templates/non_loanable_devices.html b/templates/non_loanable_devices.html
index 990d433..489cc4d 100644
--- a/templates/non_loanable_devices.html
+++ b/templates/non_loanable_devices.html
@@ -2,22 +2,22 @@
 
 {% block content %}
     <div class="section">
-        <h2>Non-Loanable Devices Inventory</h2>
-        <p>These devices are tracked in inventory but cannot be loaned to users.</p>
-        <a href="/add_non_loanable_device" class="btn">Add Non-Loanable Device</a>
+        <h2>{{ _('Non-Loanable Devices Inventory') }}</h2>
+        <p>{{ _('These devices are tracked in inventory but cannot be loaned to users.') }}</p>
+        <a href="/add_non_loanable_device" class="btn">{{ _('Add Non-Loanable Device') }}</a>
         
         {% if devices %}
             <div class="table-container">
                 <table>
                     <thead>
                         <tr>
-                            <th>Type</th>
-                            <th>Brand</th>
-                            <th>Model</th>
-                            <th>Serial Number</th>
-                            <th>Location</th>
-                            <th>Status</th>
-                            <th>Actions</th>
+                            <th>{{ _('Type') }}</th>
+                            <th>{{ _('Brand') }}</th>
+                            <th>{{ _('Model') }}</th>
+                            <th>{{ _('Serial Number') }}</th>
+                            <th>{{ _('Location') }}</th>
+                            <th>{{ _('Status') }}</th>
+                            <th>{{ _('Actions') }}</th>
                         </tr>
                     </thead>
                     <tbody>
@@ -30,8 +30,8 @@
                                 <td>{{ device.location or '-' }}</td>
                                 <td>{{ device.status }}</td>
                                 <td>
-                                    <a href="/edit_non_loanable_device/{{ device.id }}" class="btn">Edit</a>
-                                    <a href="/delete_non_loanable_device/{{ device.id }}" class="btn btn-danger" onclick="return confirm('Are you sure you want to delete this device?')">Delete</a>
+                                    <a href="/edit_non_loanable_device/{{ device.id }}" class="btn">{{ _('Edit') }}</a>
+                                    <a href="/delete_non_loanable_device/{{ device.id }}" class="btn btn-danger" onclick="return confirm('{{ _("Are you sure you want to delete this device?") }}')">{{ _('Delete') }}</a>
                                 </td>
                             </tr>
                         {% endfor %}
@@ -39,7 +39,7 @@
                 </table>
             </div>
         {% else %}
-            <p>No non-loanable devices registered.</p>
+            <p>{{ _('No non-loanable devices registered.') }}</p>
         {% endif %}
     </div>
 {% endblock %}
diff --git a/templates/project_management.html b/templates/project_management.html
index 597babd..606b1da 100644
--- a/templates/project_management.html
+++ b/templates/project_management.html
@@ -1,25 +1,25 @@
 {% extends "base.html" %}
 
 {% block content %}
-    <h2>Project Management - Development Notes</h2>
+    <h2>{{ _('Project Management - Development Notes') }}</h2>
     
     <div class="project-management-container">
         <div class="editor-section">
             <div class="editor-controls">
-                <button onclick="saveNotes()" class="btn">Save Notes</button>
-                <button onclick="loadNotes()" class="btn">Reload</button>
+                <button onclick="saveNotes()" class="btn">{{ _('Save Notes') }}</button>
+                <button onclick="loadNotes()" class="btn">{{ _('Reload') }}</button>
                 <span id="status" style="margin-left: 15px; font-style: italic;"></span>
             </div>
             
             <div class="editor-row">
                 <div class="editor-col">
-                    <h3>Editor</h3>
+                    <h3>{{ _('Editor') }}</h3>
                     <textarea id="markdown-editor" class="markdown-editor" 
-                              placeholder="Write your markdown notes here..."></textarea>
+                              placeholder="{{ _('Write your markdown notes here...') }}"></textarea>
                 </div>
                 
                 <div class="editor-col">
-                    <h3>Preview</h3>
+                    <h3>{{ _('Preview') }}</h3>
                     <div id="markdown-preview" class="markdown-preview"></div>
                 </div>
             </div>
@@ -54,13 +54,13 @@
                 .then(content => {
                     document.getElementById('markdown-editor').value = content;
                     document.getElementById('markdown-preview').innerHTML = marked.parse(content);
-                    document.getElementById('status').textContent = 'Loaded successfully';
+                    document.getElementById('status').textContent = '{{ _("Loaded successfully") }}';
                     setTimeout(() => {
                         document.getElementById('status').textContent = '';
                     }, 2000);
                 })
                 .catch(error => {
-                    document.getElementById('status').textContent = 'Using default content';
+                    document.getElementById('status').textContent = '{{ _("Using default content") }}';
                     setTimeout(() => {
                         document.getElementById('status').textContent = '';
                     }, 2000);
@@ -80,10 +80,10 @@
             })
             .then(response => {
                 if (response.ok) {
-                    statusEl.textContent = 'Saved successfully!';
+                    statusEl.textContent = '{{ _("Saved successfully!") }}';
                     statusEl.style.color = '#4CAF50';
                 } else {
-                    statusEl.textContent = 'Error saving';
+                    statusEl.textContent = '{{ _("Error saving") }}';
                     statusEl.style.color = '#f44336';
                 }
                 setTimeout(() => {
@@ -92,7 +92,7 @@
                 }, 2000);
             })
             .catch(error => {
-                statusEl.textContent = 'Error: ' + error.message;
+                statusEl.textContent = '{{ _("Error") }}: ' + error.message;
                 statusEl.style.color = '#f44336';
                 setTimeout(() => {
                     statusEl.textContent = '';