How to force the Handbrake app in Windows to use MP4 with H.265 and retain your audio quality

If H.265 (x265) in HandBrake is defaulting to MKV instead of MP4, it’s because some video/audio combinations aren’t supported in MP4 containers.

Here’s how to force MP4 with H.265 and retain your audio quality:

✅ Step-by-Step to Force MP4 with H.265 in HandBrake

1. Container:
   • Top of the main window: Set Format to MP4
   • ⚠️ Do NOT enable “Web Optimized” — it can restrict compatibility
2. Video Tab:
   • Video Codec: Select H.265 (x265)
   • Framerate: Same as source, Constant
   • Quality: Use Constant Quality RF 45–51 (extremely compressed)
   • Encoder Preset: Very Slow or Placebo (smaller files, slower)
3. Audio Tab:
   • Codec: AAC (avcodec)
     ⚠️ MP4 does not support Opus or some surround formats
   • Bitrate: 160 kbps or higher for good quality
   • Mixdown: Stereo (or match your source)
   • Sample Rate: Auto
4. Dimensions Tab (optional):
   • Reduce resolution (e.g., 1920×1080 → 640×360)
   • Anamorphic: None
   • Modulus: 2

🔧 If HandBrake still switches to MKV

That means:

• You selected unsupported audio, e.g., Opus or multi-channel DTS/AC3
• Or you used subtitle or attachment features that MP4 doesn’t allow

✅ Fix:

• Stick with AAC (Stereo) for audio
• Avoid subtitles unless they’re burned in
• Don’t add attachments like fonts or chapters

💡 TL;DR: Preset for Max Compression (H.265 in MP4)