QT (QuickTime Movie)
Apple's original digital video container that helped bring multimedia to personal computers in the early 1990s.
| Full name | QuickTime Movie |
| Extension | .qt |
| MIME type | video/quicktime |
| Developer | Apple Inc. |
| Released | 1991 |
| Type | Video container format |
| Internal structure | Hierarchical atoms (size + type fields) |
| Related formats | MOV, MPEG-4, ISO Base Media File Format |
What is a MOV file?
QT is the file extension for Apple's QuickTime Movie format. It stores video, audio, and other media tracks inside a single container file. The format was one of the first to make digital video practical on personal computers.
A QT file is a multimedia container built around a hierarchical structure of data blocks called atoms. Each atom holds either other atoms or raw media data such as video frames, audio samples, or subtitle text. The format supports multiple tracks simultaneously, so one file can carry video, stereo audio, and closed captions together. QuickTime's container design later served as the direct blueprint for the MPEG-4 file format standard.
History
Apple released QuickTime on December 2, 1991, as a multimedia extension for the Macintosh operating system. It was the first mass-market digital video format for personal computers, letting ordinary Macs play back video without dedicated hardware. Apple published the QuickTime File Format specification publicly in 2001, and the MPEG-4 committee used that specification as the foundation for the ISO Base Media File Format, which underlies MP4 files today.
Container vs codec
Every QT file is composed of atoms, the basic building blocks of the format. Each atom starts with a size field and a four-character type code, followed by its data. Container atoms nest child atoms inside them, while leaf atoms hold the actual media data in table form. The movie header atom stores timing, track count, and metadata separately from the raw media bytes, which can live in the same file or in an external referenced file.
What it is used for
- Storing video produced on or for Apple devices and older Mac software
- Archiving legacy multimedia projects from the 1990s and 2000s
- Editing workflows in Final Cut Pro and older QuickTime-based tools
- Converting to modern formats like MP4 while preserving the original source quality
How to open it
QT files open natively in Apple's QuickTime Player on macOS. On Windows and Linux, VLC media player reads QT files without any additional plugins.
Pros and cons
Strengths
- Supports multiple simultaneous tracks including video, audio, and text
- High quality codec support including ProRes and H.264
- Strong compatibility with macOS and Apple editing software
- Formed the technical basis for the widely used MP4 standard
Trade-offs
- Less common than MP4, so some non-Apple players may not handle all variants
- Apple discontinued QuickTime for Windows in 2016, limiting that platform's native support
- Older QT files may use codecs that are no longer widely supported
- Larger file sizes compared to modern MP4 with the same content when using lossless or legacy codecs
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MOV FAQ
What is the difference between a QT file and a MOV file?
They use the same QuickTime File Format internally. The .qt extension and the .mov extension both refer to QuickTime Movie files. MOV became the more common extension over time, but a player that opens one will open the other.
Can I play a QT file on Windows?
Yes. VLC media player opens QT files on Windows without any extra software. Apple stopped shipping QuickTime for Windows in 2016, so VLC is the most practical choice on that platform.
Is QT the same format that MPEG-4 is based on?
Yes. The MPEG-4 file format specification was built directly from Apple's publicly released QuickTime File Format specification from 2001. That is why MP4 and QT files share a very similar atom-based internal structure.
How do I convert a QT file to MP4?
You can convert a QT file to MP4 using an online converter or desktop software such as HandBrake or FFmpeg. Because both formats share a common ancestor, conversion is straightforward and quality loss is minimal when using the same codec.