---
title: Formats & Containers
description: Pick the output container for one-click downloads (Auto, MP4, MKV, WebM, Original) and understand the trade-offs.
---

VidBee saves merged video downloads as MP4 by default and falls back to MKV when codecs aren't compatible. You can override this from **Settings → One-Click Download → Container**.

## Container options

| Option | yt-dlp behavior | When to choose |
|---|---|---|
| **Auto (MP4/MKV)** | `--merge-output-format mp4/mkv` — prefer MP4, fall back to MKV when codecs cannot be muxed into MP4. | Default. Maximizes compatibility while avoiding mux failures (e.g. HEVC + Hi-Res audio on bilibili, WebM fragments on YouTube). |
| **MP4** | `--merge-output-format mp4 --remux-video mp4` | You need MP4 specifically (most compatible with QuickTime, iOS, social uploads). May fail on streams whose codecs MP4 cannot carry — switch back to **Auto** if you hit a `Conversion failed` error. |
| **MKV** | `--merge-output-format mkv --remux-video mkv` | Most permissive container. Carries any codec yt-dlp can deliver. |
| **WebM** | `--merge-output-format webm --remux-video webm` | Smallest files for VP9/AV1 + Opus streams from YouTube. Will fail when remote sources are AAC/H.264 only. |
| **Original (yt-dlp default)** | No `--merge-output-format` flag. | You want yt-dlp's built-in defaults (MKV when merging, source extension when single-stream). |

## Audio downloads

Container selection only applies to **video** downloads. One-click audio downloads continue to use the platform's preferred audio container (typically M4A/MP3/Opus).

## Where the setting lives

- **Desktop**: Settings → General → One-Click Download card → Container.
- **Web**: Settings page → One-Click Download → Container.

The setting is persisted instantly and applied to both manual one-click downloads and RSS subscription downloads.

## When MP4 still ends up as MKV

When **Auto** is selected and the source codec/audio combination cannot be muxed into MP4, yt-dlp writes an MKV file with the original codecs to avoid quality loss. To force MP4 anyway, switch the container to **MP4**; the download will fail with a clear codec error if it can't be muxed, instead of silently choosing MKV.

If you need MP4 from a non-MP4 source without losing the download, the alternative is to re-encode (slow, lossy). VidBee currently uses remux only — re-encoding is intentionally not exposed.