diff --git a/.htaccess b/.htaccess
index 41521d2..e75f798 100644
--- a/.htaccess
+++ b/.htaccess
@@ -20,6 +20,15 @@
     </FilesMatch>
 </IfModule>
 
+# Voice playback MIME types, including Safari/iPhone-compatible AAC in MP4.
+<IfModule mod_mime.c>
+    AddType audio/webm .webm
+    AddType audio/wav .wav
+    AddType audio/aac .aac
+    AddType audio/mp4 .m4a
+    AddType video/mp4 .mp4
+</IfModule>
+
 # Deny direct access to storage and internal PHP libraries
 <IfModule mod_rewrite.c>
     RewriteEngine On
diff --git a/README.md b/README.md
index dd6c208..dbe1224 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,7 @@ CyberChat is a framework-free PHP, SQLite, JavaScript, and HTML5 chat applicatio
 - Premium-configurable recording presence for both sending and viewing
 - Premium-configurable automatic voice sending
 - Tier-configurable automatic playback of newly received voice clips
+- Optional FFmpeg voice transcoding to iPhone-compatible AAC/M4A or H.264/AAC MP4
 - Administrator tier overrides that grant plan features without payment
 - Single-worker queued polling with cursor catch-up, request timeouts, deduplication, bounded retry backoff, and a capped browser message buffer
 - Plan-based custom username colors
@@ -29,6 +30,7 @@ CyberChat is a framework-free PHP, SQLite, JavaScript, and HTML5 chat applicatio
 - A web server with HTTPS for production
 - Write access to `db/`, `archive/`, `uploads/voice/`, and `config.json`
 - A modern browser with `MediaRecorder` for voice recording
+- Optional: FFmpeg with AAC support; `libx264` is also required for the H.264 profile
 - Optional: PDO MySQL for the MySQL/MariaDB mirror
 
 ## Installation
@@ -38,7 +40,7 @@ CyberChat is a framework-free PHP, SQLite, JavaScript, and HTML5 chat applicatio
 3. Configure Apache with the included `.htaccess`, or adapt `nginx-example.conf`.
 4. Open `admin.php` and sign in with the initial password `changeme123`.
 5. Immediately change `admin.password` in the Configuration tab.
-6. Open **Plans & Platform** to configure tiers, Mailgun, Stripe, and optional MySQL mirroring.
+6. Open **Plans & Platform** to configure tiers, Mailgun, Stripe, optional voice transcoding, and MySQL mirroring.
 
 The SQLite schema and default Free, Plus, and Pro tiers are created automatically on first use.
 
@@ -115,6 +117,21 @@ Stripe references:
 - <https://docs.stripe.com/api/checkout/sessions/create>
 - <https://docs.stripe.com/webhooks>
 
+## Voice Compatibility and FFmpeg
+
+Browsers that support WebM continue to record WebM by default. Safari and iPhone may record MP4/AAC instead, which the upload API also accepts.
+
+Under **Admin > Plans & Platform > Voice Transcoding / FFmpeg**, configure:
+
+- Enable or disable server-side transcoding
+- FFmpeg executable name or absolute path
+- `M4A / AAC-LC`, recommended for audio-only playback on iPhone, Safari, Android, and desktop
+- `MP4 / H.264 + AAC`, which adds a tiny black H.264 video track for systems requiring a conventional MP4
+- Audio bitrate and conversion timeout
+- Whether to retain the original source when conversion fails
+
+When transcoding is disabled, the original browser recording is stored. WebM remains the preferred default on supported browsers. When enabled, new uploads are converted; existing voice files are unchanged.
+
 ## Archives
 
 The application archives daily messages into:
@@ -143,7 +160,7 @@ Set a PDO MySQL DSN in the dashboard, enable the mirror, and optionally enable a
 <script>
   window.CYBERCHAT_BASE = '/chat';
 </script>
-<script src="/chat/assets/js/cyberchat-app.js?v=20260609.5"></script>
+<script src="/chat/assets/js/cyberchat-app.js?v=20260609.6"></script>
 <script>
   CyberChat.init('#my-chat');
 </script>
@@ -166,6 +183,7 @@ api/stripe-webhook.php       Stripe event synchronization
 assets/js/cyberchat-app.js   Browser application
 lib/mailer.php               Reusable Mailgun sender
 lib/stripe.php               Stripe REST client and subscription sync
+lib/voice_transcoder.php     Optional FFmpeg voice compatibility pipeline
 lib/mysql_mirror.php         Optional SQLite-to-MySQL mirror
 ```
 
diff --git a/admin.php b/admin.php
index 8405866..450db21 100644
--- a/admin.php
+++ b/admin.php
@@ -1729,6 +1729,12 @@ td.actions{white-space:nowrap;width:1px}
                   <tr><td class="mono">voice.max_duration_seconds</td><td class="dim">integer</td><td>Maximum voice clip duration</td></tr>
                   <tr><td class="mono">voice.max_upload_bytes</td><td class="dim">integer</td><td>Maximum recording upload size</td></tr>
                   <tr><td class="mono">voice.auto_play_default</td><td class="dim">bool</td><td>Queue and play incoming clips sequentially by default</td></tr>
+                  <tr><td class="mono">voice.transcoding.enabled</td><td class="dim">bool</td><td>Use FFmpeg for uploaded voice clips</td></tr>
+                  <tr><td class="mono">voice.transcoding.ffmpeg_path</td><td class="dim">string</td><td>FFmpeg executable name or absolute path</td></tr>
+                  <tr><td class="mono">voice.transcoding.profile</td><td class="dim">string</td><td>m4a_aac or mp4_h264_aac</td></tr>
+                  <tr><td class="mono">voice.transcoding.audio_bitrate_kbps</td><td class="dim">integer</td><td>AAC output bitrate from 48 to 320 kbps</td></tr>
+                  <tr><td class="mono">voice.transcoding.timeout_seconds</td><td class="dim">integer</td><td>FFmpeg upload conversion timeout</td></tr>
+                  <tr><td class="mono">voice.transcoding.fallback_to_source</td><td class="dim">bool</td><td>Retain WebM/MP4 source when conversion fails</td></tr>
                   <tr><td class="mono">security.min_password_length</td><td class="dim">integer</td><td>Min password chars</td></tr>
                   <tr><td class="mono">security.session_timeout_hours</td><td class="dim">integer</td><td>Session expiry in hours</td></tr>
                   <tr><td class="mono">security.bcrypt_cost</td><td class="dim">integer</td><td>bcrypt work factor (10–14)</td></tr>
diff --git a/api/archive.php b/api/archive.php
index 66d71d2..a6334f5 100644
--- a/api/archive.php
+++ b/api/archive.php
@@ -47,6 +47,7 @@ $payload = array_map(function(array $row): array {
         'id' => (int)$row['id'],
         'message' => $row['message'], 'message_type' => $row['message_type'],
         'voice_url' => $row['message_type'] === 'voice' && !empty($row['voice_file']) ? voicePublicPath($row['voice_file']) : null,
+        'voice_mime' => $row['voice_mime'] ?? null,
         'voice_duration' => $row['voice_duration'] !== null ? (float)$row['voice_duration'] : null,
         'created_at' => (int)$row['created_at'], 'day_key' => $row['day_key'],
     ];
diff --git a/api/config.php b/api/config.php
index 8598994..08d30e1 100644
--- a/api/config.php
+++ b/api/config.php
@@ -21,6 +21,8 @@ jsonResponse([
         'max_duration_seconds' => $config['voice']['max_duration_seconds'] ?? 60,
         'max_upload_bytes' => $config['voice']['max_upload_bytes'] ?? 12582912,
         'auto_play_default' => $config['voice']['auto_play_default'] ?? true,
+        'transcoding_enabled' => $config['voice']['transcoding']['enabled'] ?? false,
+        'output_profile' => $config['voice']['transcoding']['profile'] ?? 'm4a_aac',
     ],
     'subscriptions' => ['enabled' => $config['subscriptions']['enabled'] ?? true],
 ]);
diff --git a/api/messages.php b/api/messages.php
index 607493a..810e31e 100644
--- a/api/messages.php
+++ b/api/messages.php
@@ -1,6 +1,7 @@
 <?php
 define('CYBERCHAT_API', true);
 require_once __DIR__ . '/../bootstrap.php';
+require_once ROOT_DIR . '/lib/voice_transcoder.php';
 sendCorsHeaders();
 
 try { archiveYesterdayIfNeeded(); } catch (Throwable $e) { error_log($e->getMessage()); }
@@ -83,26 +84,48 @@ function sendVoiceMessage(): never {
     }
 
     $mime = class_exists('finfo') ? (string)(new finfo(FILEINFO_MIME_TYPE))->file($file['tmp_name']) : '';
-    $header = (string)file_get_contents($file['tmp_name'], false, null, 0, 12);
+    $header = (string)file_get_contents($file['tmp_name'], false, null, 0, 16);
     if (str_starts_with($header, "\x1A\x45\xDF\xA3")) $mime = 'audio/webm';
     elseif (str_starts_with($header, 'RIFF') && substr($header, 8, 4) === 'WAVE') $mime = 'audio/wav';
+    elseif (strlen($header) >= 8 && substr($header, 4, 4) === 'ftyp') $mime = 'audio/mp4';
+    elseif (strlen($header) >= 2 && ord($header[0]) === 0xFF && (ord($header[1]) & 0xF0) === 0xF0) $mime = 'audio/aac';
     $allowed = [
         'audio/webm' => 'webm',
         'video/webm' => 'webm',
         'audio/wav' => 'wav',
         'audio/x-wav' => 'wav',
         'audio/wave' => 'wav',
+        'audio/mp4' => 'm4a',
+        'video/mp4' => 'm4a',
+        'audio/aac' => 'aac',
+        'audio/x-aac' => 'aac',
     ];
-    if (!isset($allowed[$mime])) jsonResponse(['error' => 'Voice clips must be WAV or WebM'], 400);
+    if (!isset($allowed[$mime])) jsonResponse(['error' => 'Voice clips must be WebM, MP4/M4A, AAC, or WAV'], 400);
 
     $dir = voiceUploadDir();
     ensureWritableDirectory($dir, 'Voice storage');
-    $filename = bin2hex(random_bytes(20)) . '.' . $allowed[$mime];
-    if (!move_uploaded_file($file['tmp_name'], $dir . '/' . $filename)) {
+    $token = bin2hex(random_bytes(20));
+    $sourceFilename = $token . '.' . $allowed[$mime];
+    $sourcePath = $dir . '/' . $sourceFilename;
+    if (!move_uploaded_file($file['tmp_name'], $sourcePath)) {
         jsonResponse(['error' => 'Could not store voice clip'], 500);
     }
 
-    $storedMime = $mime === 'video/webm' ? 'audio/webm' : $mime;
+    $sourceMime = match ($mime) {
+        'video/webm' => 'audio/webm',
+        'video/mp4' => 'audio/mp4',
+        'audio/x-wav', 'audio/wave' => 'audio/wav',
+        'audio/x-aac' => 'audio/aac',
+        default => $mime,
+    };
+    try {
+        $stored = transcodeVoiceRecording($sourcePath, $sourceFilename, $sourceMime);
+    } catch (Throwable $e) {
+        if (is_file($sourcePath)) @unlink($sourcePath);
+        throw $e;
+    }
+    $filename = $stored['filename'];
+    $storedMime = $stored['mime'];
     $db = getDB();
     try {
         $db->prepare("INSERT INTO messages
diff --git a/assets/js/cyberchat-app.js b/assets/js/cyberchat-app.js
index 7aba904..93284c6 100644
--- a/assets/js/cyberchat-app.js
+++ b/assets/js/cyberchat-app.js
@@ -14,7 +14,7 @@
     loginChallenge: initialChallenge,
     verifyToken: new URLSearchParams(location.search).get('verify') || '',
     voice: { recorder: null, stream: null, timer: null, heartbeat: null, started: 0,
-      chunks: [], blob: null, duration: 0, url: '', autoSend: false, autoPlay: false,
+      chunks: [], blob: null, mime: '', duration: 0, url: '', autoSend: false, autoPlay: false,
       playQueue: [], currentAudio: null, queuePlaying: false, autoplayWarningShown: false, sending: false }
   };
   let root;
@@ -89,9 +89,11 @@
   function linkify(text) {
     return text.replace(/(https?:\/\/[^\s<>]+)/g, '<a href="$1" target="_blank" rel="noopener noreferrer">$1</a>');
   }
-  function audioPlayer(src = '', id = '') {
+  function audioPlayer(src = '', id = '', mime = '') {
     return `<span class="cc-cyber-audio">
-      <audio ${id ? `id="${id}"` : ''} preload="metadata" ${src ? `src="${esc(src)}"` : ''}></audio>
+      <audio ${id ? `id="${id}"` : ''} preload="metadata" playsinline>${src
+        ? `<source src="${esc(src)}" ${mime ? `type="${esc(mime)}"` : ''}>`
+        : ''}</audio>
       <button class="cc-audio-play" type="button" aria-label="Play audio"><span class="cc-audio-play-icon"></span></button>
       <span class="cc-audio-signal" aria-hidden="true"><i></i><i></i><i></i><i></i></span>
       <input class="cc-audio-seek" type="range" min="0" max="1000" value="0" aria-label="Audio position">
@@ -565,7 +567,7 @@
     item.dataset.id = String(id);
     item.dataset.renderKey = messageRenderKey(message);
     const content = message.message_type === 'voice' && message.voice_url
-      ? `<span class="cc-voice-message"><span class="cc-voice-label">VOICE ${duration(message.voice_duration)}</span>${audioPlayer(publicUrl(message.voice_url))}</span>`
+      ? `<span class="cc-voice-message"><span class="cc-voice-label">VOICE ${duration(message.voice_duration)}</span>${audioPlayer(publicUrl(message.voice_url), '', message.voice_mime)}</span>`
       : linkify(esc(message.message));
     item.innerHTML = `<span class="cc-msg-time">${clock(message.created_at)}</span>
       <span class="cc-msg-user" style="color:${esc(message.color)}">${esc(message.username)}</span>
@@ -636,15 +638,31 @@
     if (!navigator.mediaDevices?.getUserMedia || !window.MediaRecorder) return toast('Voice recording is not supported');
     try {
       const stream = await navigator.mediaDevices.getUserMedia({ audio: true });
-      const mime = ['audio/webm;codecs=opus', 'audio/webm'].find(type => MediaRecorder.isTypeSupported(type));
-      if (!mime) { stream.getTracks().forEach(track => track.stop()); return toast('WebM recording is not supported'); }
+      const candidates = [
+        'audio/webm;codecs=opus', 'audio/webm',
+        'audio/mp4;codecs=mp4a.40.2', 'audio/mp4', 'audio/aac'
+      ];
+      let recorder = null;
+      let mime = '';
+      for (const candidate of candidates) {
+        if (MediaRecorder.isTypeSupported && !MediaRecorder.isTypeSupported(candidate)) continue;
+        try {
+          recorder = new MediaRecorder(stream, { mimeType: candidate });
+          mime = candidate;
+          break;
+        } catch {}
+      }
+      if (!recorder) recorder = new MediaRecorder(stream);
       state.voice.stream = stream;
       state.voice.chunks = [];
       state.voice.started = Date.now();
-      const recorder = new MediaRecorder(stream, { mimeType: mime });
+      const recordedMime = recorder.mimeType || mime || 'audio/webm';
       recorder.addEventListener('dataavailable', event => { if (event.data.size) state.voice.chunks.push(event.data); });
       recorder.addEventListener('stop', () => {
-        if (!recorder._discard) finishVoice(new Blob(state.voice.chunks, { type: mime }), (Date.now() - state.voice.started) / 1000);
+        if (!recorder._discard) finishVoice(
+          new Blob(state.voice.chunks, { type: recordedMime }),
+          (Date.now() - state.voice.started) / 1000
+        );
       }, { once: true });
       recorder.start(250);
       state.voice.recorder = recorder;
@@ -680,6 +698,7 @@
   function finishVoice(blob, length) {
     if (!blob.size || length < 0.25) return toast('Voice clip was too short');
     state.voice.blob = blob;
+    state.voice.mime = blob.type || 'audio/webm';
     state.voice.duration = length;
     if (state.voice.autoSend && feature('auto_voice_send')) return sendVoice();
     if (state.voice.url) URL.revokeObjectURL(state.voice.url);
@@ -694,6 +713,7 @@
     if (state.voice.url) URL.revokeObjectURL(state.voice.url);
     state.voice.url = '';
     state.voice.blob = null;
+    state.voice.mime = '';
     state.voice.duration = 0;
     if ($('#voice-review')) $('#voice-review').hidden = true;
   }
@@ -703,7 +723,10 @@
     const body = new FormData();
     body.append('action', 'send_voice');
     body.append('duration', state.voice.duration.toFixed(2));
-    body.append('voice', state.voice.blob, 'voice.webm');
+    const uploadName = state.voice.mime.includes('mp4') ? 'voice.m4a'
+      : state.voice.mime.includes('aac') ? 'voice.aac'
+        : state.voice.mime.includes('wav') ? 'voice.wav' : 'voice.webm';
+    body.append('voice', state.voice.blob, uploadName);
     const result = await api('messages.php', { method: 'POST', body })
       .catch(() => ({ error: 'Voice send failed. Polling will continue.' }));
     state.voice.sending = false;
@@ -729,7 +752,7 @@
   }
   function archiveRow(message) {
     const content = message.message_type === 'voice' && message.voice_url
-      ? audioPlayer(publicUrl(message.voice_url)) : esc(message.message);
+      ? audioPlayer(publicUrl(message.voice_url), '', message.voice_mime) : esc(message.message);
     return `<div class="cc-archive-row"><time>${esc(message.day_key)} ${clock(message.created_at)}</time>
       <span class="cc-type-tag">${esc(message.message_type)}</span><div>${content}</div></div>`;
   }
diff --git a/config.json b/config.json
index 5460c55..42a9d92 100644
--- a/config.json
+++ b/config.json
@@ -24,7 +24,15 @@
     "max_duration_seconds": 60,
     "max_upload_bytes": 12582912,
     "auto_play_default": true,
-    "upload_dir": "uploads/voice"
+    "upload_dir": "uploads/voice",
+    "transcoding": {
+      "enabled": false,
+      "ffmpeg_path": "ffmpeg",
+      "profile": "m4a_aac",
+      "audio_bitrate_kbps": 128,
+      "timeout_seconds": 45,
+      "fallback_to_source": true
+    }
   },
   "database": {
     "main_db": "db/chat.sqlite",
diff --git a/embed-example.html b/embed-example.html
index afa2c40..9116571 100644
--- a/embed-example.html
+++ b/embed-example.html
@@ -94,7 +94,7 @@
 <span class="kw">&lt;div</span> id=<span class="str">"my-chat"</span> style=<span class="str">"width:100%; height:600px"</span><span class="kw">&gt;&lt;/div&gt;</span>
 
 <span class="cm">&lt;!-- 4. Script + init --&gt;</span>
-<span class="kw">&lt;script</span> src=<span class="str">"assets/js/cyberchat-app.js?v=20260609.5"</span><span class="kw">&gt;&lt;/script&gt;</span>
+<span class="kw">&lt;script</span> src=<span class="str">"assets/js/cyberchat-app.js?v=20260609.6"</span><span class="kw">&gt;&lt;/script&gt;</span>
 <span class="kw">&lt;script&gt;</span>
   window.CYBERCHAT_BASE = <span class="str">'/path/to/cyberchat'</span>; <span class="cm">// adjust to your install path</span>
   CyberChat.init(<span class="str">'#my-chat'</span>);
@@ -104,7 +104,7 @@
 <script>
   window.CYBERCHAT_BASE = '';
 </script>
-  <script src="assets/js/cyberchat-app.js?v=20260609.5"></script>
+  <script src="assets/js/cyberchat-app.js?v=20260609.6"></script>
 <script>
   document.addEventListener('DOMContentLoaded', function() {
     CyberChat.init('#chat-here');
diff --git a/index.html b/index.html
index 37221ab..ad38b97 100644
--- a/index.html
+++ b/index.html
@@ -17,7 +17,7 @@
   <script>
     window.CYBERCHAT_BASE = '';
   </script>
-  <script src="assets/js/cyberchat-app.js?v=20260609.5"></script>
+  <script src="assets/js/cyberchat-app.js?v=20260609.6"></script>
   <script>
     document.addEventListener('DOMContentLoaded', function() {
       CyberChat.init('#app');
diff --git a/lib/admin_platform.php b/lib/admin_platform.php
index 074bd00..b7facf0 100644
--- a/lib/admin_platform.php
+++ b/lib/admin_platform.php
@@ -2,6 +2,8 @@
 
 function handleAdminPlatformAction(string $action): ?string {
     if ($action === 'save_platform_services') {
+        $voiceProfile = (string)($_POST['voice_transcoding_profile'] ?? 'm4a_aac');
+        if (!in_array($voiceProfile, ['m4a_aac', 'mp4_h264_aac'], true)) $voiceProfile = 'm4a_aac';
         setConfigValues([
             'subscriptions.enabled' => !empty($_POST['subscriptions_enabled']),
             'mailgun.api_key' => trim((string)($_POST['mailgun_api_key'] ?? '')),
@@ -13,6 +15,12 @@ function handleAdminPlatformAction(string $action): ?string {
             'stripe.success_url' => trim((string)($_POST['stripe_success_url'] ?? '')),
             'stripe.cancel_url' => trim((string)($_POST['stripe_cancel_url'] ?? '')),
             'stripe.portal_return_url' => trim((string)($_POST['stripe_portal_return_url'] ?? '')),
+            'voice.transcoding.enabled' => !empty($_POST['voice_transcoding_enabled']),
+            'voice.transcoding.ffmpeg_path' => trim((string)($_POST['voice_ffmpeg_path'] ?? 'ffmpeg')) ?: 'ffmpeg',
+            'voice.transcoding.profile' => $voiceProfile,
+            'voice.transcoding.audio_bitrate_kbps' => max(48, min(320, (int)($_POST['voice_audio_bitrate'] ?? 128))),
+            'voice.transcoding.timeout_seconds' => max(5, min(300, (int)($_POST['voice_transcoding_timeout'] ?? 45))),
+            'voice.transcoding.fallback_to_source' => !empty($_POST['voice_transcoding_fallback']),
             'database.mysql.enabled' => !empty($_POST['mysql_enabled']),
             'database.mysql.auto_import' => !empty($_POST['mysql_auto_import']),
             'database.mysql.dsn' => trim((string)($_POST['mysql_dsn'] ?? '')),
@@ -158,6 +166,32 @@ function renderAdminPlatformTab(): void {
         <p class="dim">Webhook endpoint: <span class="mono"><?= esc(appBaseUrl() . '/api/stripe-webhook.php') ?></span></p>
       </div></div>
 
+      <div class="panel"><div class="panel-head"><span class="panel-title">// VOICE TRANSCODING / FFMPEG</span></div><div class="panel-body">
+        <label class="cb-row"><input type="checkbox" name="voice_transcoding_enabled"
+          <?= getConfigVal('voice.transcoding.enabled', false) ? 'checked' : '' ?>>
+          <span>Transcode uploaded voice clips for broader playback compatibility</span></label>
+        <div class="form-row3">
+          <div class="field"><label>FFmpeg Binary</label><input name="voice_ffmpeg_path"
+            value="<?= esc(getConfigVal('voice.transcoding.ffmpeg_path', 'ffmpeg')) ?>" placeholder="/usr/bin/ffmpeg"></div>
+          <div class="field"><label>Output Profile</label><select name="voice_transcoding_profile">
+            <?php $voiceProfile = getConfigVal('voice.transcoding.profile', 'm4a_aac'); ?>
+            <option value="m4a_aac" <?= $voiceProfile === 'm4a_aac' ? 'selected' : '' ?>>M4A / AAC-LC (recommended)</option>
+            <option value="mp4_h264_aac" <?= $voiceProfile === 'mp4_h264_aac' ? 'selected' : '' ?>>MP4 / H.264 + AAC</option>
+          </select></div>
+          <div class="field"><label>Audio Bitrate (kbps)</label><input type="number" min="48" max="320"
+            name="voice_audio_bitrate" value="<?= (int)getConfigVal('voice.transcoding.audio_bitrate_kbps', 128) ?>"></div>
+        </div>
+        <div class="form-row">
+          <div class="field"><label>Conversion Timeout (seconds)</label><input type="number" min="5" max="300"
+            name="voice_transcoding_timeout" value="<?= (int)getConfigVal('voice.transcoding.timeout_seconds', 45) ?>"></div>
+          <label class="cb-row"><input type="checkbox" name="voice_transcoding_fallback"
+            <?= getConfigVal('voice.transcoding.fallback_to_source', true) ? 'checked' : '' ?>>
+            <span>Keep the original recording if FFmpeg fails</span></label>
+        </div>
+        <p class="dim">AAC-LC in an M4A container is the recommended audio-only profile for iPhone, Safari, Android, and desktop browsers.
+          The H.264 profile creates a tiny black video track plus AAC audio for systems that require a conventional MP4 file.</p>
+      </div></div>
+
       <div class="panel"><div class="panel-head"><span class="panel-title">// OPTIONAL MYSQL / MARIADB MIRROR</span></div><div class="panel-body">
         <label class="cb-row"><input type="checkbox" name="mysql_enabled" <?= getConfigVal('database.mysql.enabled', false) ? 'checked' : '' ?>><span>Enable MySQL mirror</span></label>
         <label class="cb-row"><input type="checkbox" name="mysql_auto_import" <?= getConfigVal('database.mysql.auto_import', false) ? 'checked' : '' ?>><span>Automatically import all SQLite databases on the configured interval</span></label>
diff --git a/lib/voice_transcoder.php b/lib/voice_transcoder.php
new file mode 100644
index 0000000..3a9a09d
--- /dev/null
+++ b/lib/voice_transcoder.php
@@ -0,0 +1,160 @@
+<?php
+
+function voiceTranscodingProfile(): string {
+    $profile = (string)getConfigVal('voice.transcoding.profile', 'm4a_aac');
+    return in_array($profile, ['m4a_aac', 'mp4_h264_aac'], true) ? $profile : 'm4a_aac';
+}
+
+function voiceFfmpegBinary(): string {
+    $binary = trim((string)getConfigVal('voice.transcoding.ffmpeg_path', 'ffmpeg'));
+    if ($binary === '' || preg_match('/[\x00-\x1F\x7F]/', $binary)) {
+        throw new RuntimeException('The FFmpeg binary path is invalid.');
+    }
+    return $binary;
+}
+
+function runVoiceTranscodeCommand(array $command, int $timeoutSeconds): array {
+    if (!function_exists('proc_open')) {
+        return ['exit_code' => 127, 'stderr' => 'PHP proc_open is unavailable.'];
+    }
+
+    $process = @proc_open($command, [
+        0 => ['pipe', 'r'],
+        1 => ['pipe', 'w'],
+        2 => ['pipe', 'w'],
+    ], $pipes, null, null, ['bypass_shell' => true]);
+    if (!is_resource($process)) {
+        return ['exit_code' => 127, 'stderr' => 'FFmpeg could not be started.'];
+    }
+
+    fclose($pipes[0]);
+    stream_set_blocking($pipes[1], false);
+    stream_set_blocking($pipes[2], false);
+    $stdout = '';
+    $stderr = '';
+    $started = microtime(true);
+    $exitCode = -1;
+
+    while (true) {
+        $stdout .= (string)stream_get_contents($pipes[1]);
+        $stderr .= (string)stream_get_contents($pipes[2]);
+        $status = proc_get_status($process);
+        if (!$status['running']) {
+            $exitCode = (int)$status['exitcode'];
+            break;
+        }
+        if ((microtime(true) - $started) >= $timeoutSeconds) {
+            proc_terminate($process);
+            usleep(100000);
+            $status = proc_get_status($process);
+            if ($status['running']) proc_terminate($process, 9);
+            $exitCode = 124;
+            $stderr .= "\nFFmpeg timed out.";
+            break;
+        }
+        usleep(50000);
+    }
+
+    $stdout .= (string)stream_get_contents($pipes[1]);
+    $stderr .= (string)stream_get_contents($pipes[2]);
+    fclose($pipes[1]);
+    fclose($pipes[2]);
+    $closeCode = proc_close($process);
+    if ($exitCode < 0) $exitCode = $closeCode;
+
+    return [
+        'exit_code' => $exitCode,
+        'stdout' => substr($stdout, -4000),
+        'stderr' => substr($stderr, -4000),
+    ];
+}
+
+function transcodeVoiceRecording(
+    string $sourcePath,
+    string $sourceFilename,
+    string $sourceMime
+): array {
+    if (!getConfigVal('voice.transcoding.enabled', false)) {
+        return ['filename' => $sourceFilename, 'mime' => $sourceMime, 'transcoded' => false];
+    }
+
+    $profile = voiceTranscodingProfile();
+    $bitrate = max(48, min(320, (int)getConfigVal('voice.transcoding.audio_bitrate_kbps', 128)));
+    $timeout = max(5, min(300, (int)getConfigVal('voice.transcoding.timeout_seconds', 45)));
+    $fallback = (bool)getConfigVal('voice.transcoding.fallback_to_source', true);
+    $token = pathinfo($sourceFilename, PATHINFO_FILENAME);
+    if (!preg_match('/^[a-f0-9]{40}$/', $token)) {
+        throw new RuntimeException('Voice recording filename is invalid.');
+    }
+
+    $extension = $profile === 'mp4_h264_aac' ? 'mp4' : 'm4a';
+    $outputMime = $profile === 'mp4_h264_aac' ? 'video/mp4' : 'audio/mp4';
+    $outputFilename = $token . '.' . $extension;
+    $outputPath = dirname($sourcePath) . '/' . $outputFilename;
+    $temporaryPath = dirname($sourcePath) . '/.' . $token . '.tmp.' . $extension;
+    $binary = voiceFfmpegBinary();
+
+    if ($profile === 'mp4_h264_aac') {
+        $command = [
+            $binary, '-nostdin', '-hide_banner', '-loglevel', 'error', '-y',
+            '-f', 'lavfi', '-i', 'color=c=black:s=16x16:r=1',
+            '-i', $sourcePath,
+            '-map', '0:v:0', '-map', '1:a:0', '-shortest',
+            '-c:v', 'libx264', '-preset', 'veryfast', '-tune', 'stillimage',
+            '-profile:v', 'baseline', '-level', '3.0', '-pix_fmt', 'yuv420p',
+            '-c:a', 'aac', '-profile:a', 'aac_low', '-b:a', $bitrate . 'k',
+            '-map_metadata', '-1', '-movflags', '+faststart', $temporaryPath,
+        ];
+    } else {
+        $command = [
+            $binary, '-nostdin', '-hide_banner', '-loglevel', 'error', '-y',
+            '-i', $sourcePath, '-vn',
+            '-c:a', 'aac', '-profile:a', 'aac_low', '-b:a', $bitrate . 'k',
+            '-map_metadata', '-1', '-movflags', '+faststart', $temporaryPath,
+        ];
+    }
+
+    $result = runVoiceTranscodeCommand($command, $timeout);
+    $validOutput = $result['exit_code'] === 0
+        && is_file($temporaryPath)
+        && filesize($temporaryPath) > 0;
+    if (!$validOutput) {
+        if (is_file($temporaryPath)) @unlink($temporaryPath);
+        $detail = trim((string)($result['stderr'] ?? ''));
+        error_log('Voice transcoding failed: ' . ($detail !== '' ? $detail : 'unknown FFmpeg error'));
+        if ($fallback) {
+            return ['filename' => $sourceFilename, 'mime' => $sourceMime, 'transcoded' => false];
+        }
+        throw new RuntimeException('Voice transcoding failed. Check the FFmpeg dashboard settings.');
+    }
+
+    $sourceBackupPath = null;
+    if ($outputPath === $sourcePath) {
+        $sourceBackupPath = dirname($sourcePath) . '/.' . $token . '.source.' . $extension;
+        if (!@rename($sourcePath, $sourceBackupPath)) {
+            @unlink($temporaryPath);
+            if ($fallback) {
+                return ['filename' => $sourceFilename, 'mime' => $sourceMime, 'transcoded' => false];
+            }
+            throw new RuntimeException('The original voice clip could not be prepared for replacement.');
+        }
+    }
+
+    if (!@rename($temporaryPath, $outputPath)) {
+        @unlink($temporaryPath);
+        if ($sourceBackupPath !== null && is_file($sourceBackupPath)) {
+            @rename($sourceBackupPath, $sourcePath);
+        }
+        if ($fallback && is_file($sourcePath)) {
+            return ['filename' => $sourceFilename, 'mime' => $sourceMime, 'transcoded' => false];
+        }
+        throw new RuntimeException('The transcoded voice clip could not be stored.');
+    }
+
+    if ($sourceBackupPath !== null) {
+        @unlink($sourceBackupPath);
+    } else {
+        @unlink($sourcePath);
+    }
+    return ['filename' => $outputFilename, 'mime' => $outputMime, 'transcoded' => true];
+}
diff --git a/nginx-example.conf b/nginx-example.conf
index cc66cba..11dc6d5 100644
--- a/nginx-example.conf
+++ b/nginx-example.conf
@@ -39,6 +39,26 @@ server {
         return 404;
     }
 
+    location ~* ^/uploads/voice/.*\.m4a$ {
+        default_type audio/mp4;
+        try_files $uri =404;
+    }
+
+    location ~* ^/uploads/voice/.*\.aac$ {
+        default_type audio/aac;
+        try_files $uri =404;
+    }
+
+    location ~* ^/uploads/voice/.*\.webm$ {
+        default_type audio/webm;
+        try_files $uri =404;
+    }
+
+    location ~* ^/uploads/voice/.*\.mp4$ {
+        default_type video/mp4;
+        try_files $uri =404;
+    }
+
     # PHP files
     location ~ \.php$ {
         fastcgi_pass unix:/run/php/php8.1-fpm.sock; # adjust PHP version