diff --git a/devterm/templates/base64.html b/devterm/templates/base64.html
new file mode 100644
index 0000000..140426f
--- /dev/null
+++ b/devterm/templates/base64.html
@@ -0,0 +1,109 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Base64 Tool - Devterm</title>
+    <style>
+        * { margin: 0; padding: 0; box-sizing: border-box; }
+        body {
+            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+            background: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
+            min-height: 100vh;
+            color: #fff;
+        }
+        .container { max-width: 1200px; margin: 0 auto; padding: 2rem; }
+        header {
+            display: flex;
+            align-items: center;
+            gap: 1rem;
+            padding-bottom: 1rem;
+            border-bottom: 1px solid rgba(255,255,255,0.1);
+            margin-bottom: 2rem;
+        }
+        h1 { font-size: 1.5rem; background: linear-gradient(90deg, #00d4ff, #7c3aed); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
+        .back-link { color: #94a3b8; text-decoration: none; }
+        .back-link:hover { color: #00d4ff; }
+        .grid { display: grid; grid-template-columns: 1fr 1fr; gap: 1.5rem; }
+        .panel { background: rgba(255,255,255,0.05); border: 1px solid rgba(255,255,255,0.1); border-radius: 12px; overflow: hidden; }
+        .panel-header { padding: 1rem; border-bottom: 1px solid rgba(255,255,255,0.1); font-weight: 600; }
+        textarea {
+            width: 100%;
+            height: 300px;
+            background: transparent;
+            border: none;
+            color: #e2e8f0;
+            padding: 1rem;
+            font-family: 'Monaco', 'Menlo', monospace;
+            font-size: 14px;
+            resize: none;
+        }
+        textarea:focus { outline: none; }
+        .actions { display: flex; gap: 1rem; margin: 1.5rem 0; }
+        button {
+            background: linear-gradient(90deg, #00d4ff, #7c3aed);
+            border: none;
+            color: white;
+            padding: 0.75rem 1.5rem;
+            border-radius: 8px;
+            cursor: pointer;
+            font-weight: 600;
+            transition: opacity 0.2s;
+        }
+        button:hover { opacity: 0.9; }
+        .error { color: #ef4444; }
+        .success { color: #22c55e; }
+    </style>
+</head>
+<body>
+    <div class="container">
+        <header>
+            <a href="/" class="back-link">←</a>
+            <h1>Base64 Encoder/Decoder</h1>
+        </header>
+        <div class="grid">
+            <div class="panel">
+                <div class="panel-header">Input</div>
+                <textarea id="input" placeholder="Enter text or paste Base64..."></textarea>
+            </div>
+            <div class="panel">
+                <div class="panel-header">Output</div>
+                <textarea id="output" readonly></textarea>
+            </div>
+        </div>
+        <div class="actions">
+            <button onclick="encode()">Encode →</button>
+            <button onclick="decode()">← Decode</button>
+            <button onclick="clearAll()">Clear</button>
+        </div>
+    </div>
+    <script>
+        async function encode() {
+            const input = document.getElementById('input').value;
+            if (!input.trim()) return;
+            const res = await fetch('/base64/encode', { method: 'POST', body: input });
+            const data = await res.json();
+            if (data.error) {
+                alert('Error: ' + data.error);
+            } else {
+                document.getElementById('output').value = data.result;
+            }
+        }
+        async function decode() {
+            const input = document.getElementById('input').value;
+            if (!input.trim()) return;
+            const res = await fetch('/base64/decode', { method: 'POST', body: input });
+            const data = await res.json();
+            if (data.error) {
+                alert('Error: ' + data.error);
+            } else {
+                document.getElementById('output').value = data.result;
+            }
+        }
+        function clearAll() {
+            document.getElementById('input').value = '';
+            document.getElementById('output').value = '';
+        }
+    </script>
+</body>
+</html>
