Difference Between AAC and M4A (with Table)

The difference between AAC and M4A is that the former is an encoding system used to compress audio files while the latter refers to a file extension format.

A distinct coding mechanism is embodied in AAC that produces an enhanced audio experience while occupying minimal storage. The M4A file extension is used in conjunction with AAC as representative of audio files stored using this coding system.

There may be other extensions –like MP4- used with the AAC format, however, M4A remains one of the most commonly used extensions, especially by popular platforms like iTunes.

The seminal difference between the two remains that AAC is an audio codec and M4A is a file container that is commonly used for the AAC format.

Comparison Table Between AAC and M4A

Parameters of ComparisonAACM4A
DefinitionAAC is an audio coding system originally developed as an improvement on the mp3 format.M4A is the file extension format used with the AAC.
System TypeEncoding systemFile container
Contained ByMPEG-2 and MPEG-4MPEG-4
CodecAAC is a codec. It is a lossy compression codec that reduces the size of an audio file without compromising its quality, although a part of the data is lost in compression.  M4A is not a codec. It is simply a file container commonly used with the ACC codec. There are other file containers like .acc, .mp4 that can also be used with ACC codecs.
Kind Of Audio Compression SupportedAAC is solely a lossy compression codec.      M4A can be used with either a lossy compression or a lossless compression codec like ALAC.    

What is AAC?

Advanced Audio Coding or AAC is an audio file format that was launched in 1997 as an improved successor to the mp3 format. This upgraded version boasts a higher power of compressing audio files while using minimum space. AAC claims to offer enhanced sound quality at the existing mp3 bit rate. AAC is a part of the MPEG-2 and MPEG-4 specifications.

This coding system operates as a lossy file format to deliver an enriched audio experience by effectively removing excess data from the file without compromising its audio quality. AAC is the customary audio file format used by a number of platforms including popular forums like iTunes, Nintendo, PlayStation 3.

AAC was the result of a drive to improve upon the existent audio coding systems. Sony, Nokia, AT&T Bell Laboratories, Dolby and Fraunhofer Institute teamed up to create the AAC codec. The sample frequencies of AAC – ranging from 8 kHz to 96 kHz- are much more extensive than its predecessor.

Compression without a quality compromise is feasible in AAC formats due to the flexibility offered by the coding system. The Temporal Noise Shaping feature aids in achieving superior compression standards without distorting sound quality.


What is M4A?

M4A represents a MPEG-4 audio file extension. It is a file extension format commonly used with AAC. The AAC lossy compression technique is implemented to reduce the size of the audio file while retaining its superior soundscape. The .m4a format is often used to save such compressed files.

Since the AAC format is used extensively by iTunes, the M4A file extension format is also popularly used by the same platform. The distinguishing feature of M4A file extensions is that they can be used to save both lossy and lossless compression formats.

Sometimes files need to be renamed in order to access them as certain platform may not support the given file extension format. Video files do not use this extension format. Audio files with the M4A file extensions can be successfully accessed on the Windows Media Player, Roxio Popcorn, Quicktime and others.

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Main Differences Between AAC and M4A

  1. The main difference between AAC and M4A is that the former denotes an audio codec and the latter is a file extension commonly used with these audio codec files.
  2. M4A files are part of the MPEG-4 audio system. While AAC is a part of both MPEG-2 and MPEG-4 specifications.
  3. AAC is an encoding system that operates to code audio data in a lossy compression format. M4A is a file extension and container that is frequently used with AAC files.
  4. M4A files are usually encoded with the lossy compression of the AAC codec, however, they may also be encoded with the lossless ALAC codec. Alternatively, AAC formats are always lossy compression formats. They compress audio files at the mp3 bit rate with a small loss of data.
  5. AAC is a codec system that was developed as a novel improvement over the mp3. It encodes audio data. On the other hand, M4A is not a codec but simply a file container. There can be other file containers used with AAC like .acc, .mp4, .m4b, etc.
  6. Unprotected AAC files have the M4A extension, while the protected versions have the M4P file extension.


There exist significant differences between AAC and M4A in terms of the system specifications they operate under, their typology as well as their function.

There are also similarities between the two as both are commonly used together. They can both be converted into mp3 formats and they are both solely audio formats. Both these file formats have been popularized by similar platforms like iTunes, Nintendo and others.

However, the salient difference is witnessed in terms of their functionality and their typology. AAC is essentially a coding system. It is a lossy compression codec that works to maintain sound quality by occupying lesser space. Whereas, M4A is simple a file extension container that is usually associated with AAC.

The container type can be altered easily from ,m4a to .aac. Their operation specifications also differ in that the former operates under MPEG-2 and 4 while the latter solely operates under MPEG-4. M4A can be used with lossless compression codecs as well, hence its usage is not solely limited for the AAC codec.


  1. http://www.aes.org/e-lib/browse.cfm?elib=8079
  2. https://www.sciencedirect.com/science/article/pii/S1742287618300665