What Is an MP4 File (and How Do I Open One)?

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Key Takeaways

  • MP4 files are a widely used video format for downloading and streaming online videos.
  • Most video players, including default players on Windows and macOS, support MP4 files. Other video players can be easily associated with MP4 files if desired.

A file with the .mp4 file extension is an MPEG-4 video file format. MP4s are one of the more common video file formats used for downloading and streaming videos from the internet. But who created them, and how do you open one?

What Is an MP4 File?

An MP4 file is a compressed video file format. MP4s can also contain audio data or subtitles in addition to video data.

MP4 files were created under the ISO/IEC 14496-12:2001 standard by the ISO/IEC and Motion Picture Experts Group (MPEG). Because of this, MP4 is an international standard for audio-visual coding.

Initially created in 2001, MPEG-4 Part 12 was based on the QuickTime File Format (.MOV). The current version—MPEG-4 Part 14—was released in 2003. MP4 is considered a digital multimedia container format—essentially a file containing a bunch of data that’s been compressed. The standard specifies how the data is stored within the container itself, but not how that data is encoded.

MP4s are a compressed format—the video file has been shrunk so it uses up less space on your PC or phone, or when it is streamed on the Internet. The process of compressing the file does result in some loss of quality, however the exact loss will depend on which compression algorithm is used. Some, like H.265, manage to create even smaller files without appreciably hurting visual fidelity. This makes MP4 a portable and web-friendly video format.

While MP4 files can play audio, they shouldn’t be confused with M4A or MP3, as these are file formats that only contain audio.

How Do I Open an MP4 File?

Because MP4 is a standardized file format for video, almost all video players support MP4. To open a file, all you have to do is double-click your video, and it will open with your operating system’s default video viewer. Android and iPhone natively support playback of MP4 as well—just tap the file, and you’ll be watching your video in no time.

Windows and macOS users can play MP4 files without having to install any third-party software. Windows currently uses the Movies and TV by default; in macOS, they’re played using QuickTime.

An MP4 recording of a Rocket League game.

If, however, you prefer a different video player than either of those, you can pretty easily change the app associated with MP4 files on Windows, and it isn’t hard to change in macOS either. And you most likely won’t even have to do that. When you install a new video playback app, the chances are high that the new app will claim the association with MP4 files during installation, unless specified otherwise. VLC is a popular third-party application the supports MP4s and most other video formats.


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