Convert MKV to MP4 Online

How to convert MKV to MP4

1. 1

   Add MKV files

   Drop one or more Matroska videos into the queue. The server reads the primary video and audio streams.

2. 2

   Choose output quality

   Set the video quality and optional dimensions in Options. A high quality value is safer for detailed footage.

3. 3

   Convert and download

   Run the queue and download the MP4 files individually or as a ZIP.

Matroska video vs MPEG-4 Part 14 video

Why convert MKV to MP4?

• Play an MKV file on an iPhone, Android phone, browser, or smart TV that expects MP4.
• Upload to a service that accepts MP4 but does not recognize Matroska.
• Standardize a media library around H.264 and AAC for predictable playback.
• Create a smaller delivery copy from an archive file without keeping every subtitle track.

Will quality change?

The video is decoded and re-encoded to H.264, so this is a lossy transcode, not a passthrough remux. High-bitrate sources may lose some fine detail, and subtitles, attachments, and chapters are not preserved by this path. Audio is converted to AAC. Check the result before replacing an archive copy.

Processing and limits

Processing

Server-side

Engine

FFmpeg with libx264 and AAC

Maximum size

100 MB per file.

Batch support

Yes, multiple MKV files can be queued.

Quality controls

Video quality control and optional resizing. Higher quality preserves more detail and creates a larger file.

The MKV is uploaded over HTTPS and processed by FFmpeg on the server. The output is an MP4 with H.264 video, AAC audio, and fast-start metadata. Temporary files are removed after conversion.

• Subtitles, chapters, and attachment tracks are not carried into the MP4 output.
• MKV can contain codecs that require a full re-encode, so quality loss is possible.
• The 100 MB upload limit is restrictive for full-length movies.

Platform compatibility

MP4 with H.264 and AAC is broadly supported on phones, tablets, browsers, smart TVs, and game consoles. MKV is excellent for archives but less predictable on consumer playback devices, which is why this conversion is common.

When not to convert

• Keep the MKV if you need multiple subtitle tracks, chapters, or an archive of the original codecs.
• Use a remux tool instead when the video and audio codecs are already MP4-compatible and you only need to change the container.
• Do not convert a full movie through a 100 MB upload limit without trimming or using a local tool.

Frequently asked questions

Does MKV to MP4 keep subtitles?

No. This conversion path does not preserve subtitle or attachment tracks. Use a subtitle-aware tool if captions must remain selectable.

Is the conversion a remux or a re-encode?

It is a re-encode to H.264 and AAC. A remux would only change the container, but this path standardizes the codecs for broad playback.

Why is the MP4 smaller than the MKV?

H.264 at the selected quality can compress more aggressively than the source codec. The tradeoff is possible loss of fine detail, not a free size reduction.

Can I convert a 4K MKV?

The upload limit is the first constraint. Large 4K files may exceed 100 MB and take longer to process. Use a local tool for feature-length 4K sources.

Will the audio stay in sync?

FFmpeg preserves the primary audio timing during a normal transcode. Unusual variable-frame-rate sources can still need review after conversion.

Can I batch convert MKV files?

Yes. Queue multiple files, run them together, and download the MP4s as a ZIP. Each file is limited to 100 MB.