In-Depth Guide to Choosing Between MP4, WebM, and MKV Video Containers

A video container is a file format that encapsulates data such as video codec, audio codec, and subtitles. It is equivalent to a box that holds different items, while the codec is the compressed audio and video content stored inside the box itself.

A single container can encapsulate content with multiple different codecs. For example, MP4 can hold both H.264 encoded video and H.265 encoded video. Containers and codecs do not have an absolute binding relationship.

MP4 was introduced by the International Organization for Standardization (ISO), with the design goal of adapting to general playback scenarios. It supports the vast majority of consumer electronic devices and mainstream playback software, and is currently the most widely used video container.

WebM was introduced by Google, with the design goal of adapting to open-source web scenarios. The format itself is open-source and royalty-free, can be directly embedded into web pages for streaming playback, and is one of the video containers specified in the HTML5 standard.

MKV was introduced by the Matroska Association, with the design goal of serving the archiving needs of enthusiasts. It supports encapsulating arbitrary multimedia data such as multiple audio tracks, multiple subtitles, and chapter information, and can accommodate almost all codec formats.

The most mainstream codec combination for MP4 is H.264 video plus AAC audio. This combination supports hardware-accelerated decoding and playback on all hardware devices released after 2010, and has far higher compatibility than other combinations.

The standard codec combination for WebM is VP9 video plus Opus audio. This combination aligns with WebM's open-source positioning, and occupies less storage space than H.264+AAC at the same image quality.

MKV has no fixed standard codec combination. It supports encapsulation of audio and video data with any codec, and common combinations include H.265 plus FLAC, which is used for archiving original high-definition video resources.

The table below summarizes the decoding support of the three containers in native players, grouped by device type and system generation. Compatibility mainly depends on whether the device chip integrates the corresponding hardware decoding module, and whether the operating system pre-installs the container demultiplexer.

MP4 files store the moov atom (the data block that stores video index information) and the mdat atom (the data block that stores actual audio and video content) in different locations of the file. The faststart feature moves the moov atom to the beginning of the file.

When users need online streaming playback, or upload an MP4 to a video platform, enabling faststart allows the player to start playback before the entire file is downloaded. If this feature is not enabled, playback can only start after the download is complete.