Free M4A sample files
AAC audio in an MP4 container: the format of iTunes purchases and iPhone voice memos. Download valid M4A test files in 4 exact sizes, from 100 KB to 5 MB, each with a checksum.
- Extension
- .m4a
- MIME type
- audio/mp4
- Kind
- Binary
- Category
- Audio
M4A files by size
Every file below is a valid MPEG-4 audio file of exactly the stated size. Open a file's page for its checksum and contents, and to preview it in your browser before downloading.
| File | Size | Contents | Download |
|---|---|---|---|
| 100 KB M4A samplesample-m4a-100kb.m4a | 100 KB102,400 bytes | 6.3 s | Download M4A |
| 500 KB M4A samplesample-m4a-500kb.m4a | 500 KB512,000 bytes | 31.8 s | Download M4A |
| 1 MB M4A samplesample-m4a-1mb.m4a | 1 MB1,048,576 bytes | 1 min 5 s | Download M4A |
| 5 MB M4A samplesample-m4a-5mb.m4a | 5 MB5,242,880 bytes | 5 min 26 s | Download M4A |
What is an M4A file?
An M4A file is an MP4 file that holds only audio. The container is the same nested-box structure as video MP4, and the extension tells software, and people, that there is no picture. The audio is nearly always AAC, the successor to MP3, though the same container can carry lossless ALAC.
As with video, the "moov" box is the index. If it sits at the front, playback can start while the file is still downloading; if an encoder leaves it at the end, the player needs the whole file first.
How to recognise an M4A file
Software recognises an M4A file by its file signature: fixed bytes at the start of the file, also called magic bytes or a magic number.
| Extension | .m4a |
|---|---|
| MIME type | audio/mp4 |
| Also seen as | audio/x-m4a, audio/m4a |
| Container | ISO base media file format (ISO/IEC 14496-12) |
| Usual codec | AAC-LC (ISO/IEC 14496-3); sometimes ALAC |
| Frame length | 1,024 samples for AAC-LC |
| Related extensions | .m4b audiobooks, .m4r ringtones, .mp4 |
What to test for
These are the behaviours that most often go wrong when software handles M4A files.
- The container is the same as MP4 video, so content sniffers often report video/mp4. Telling them apart takes a look at the ftyp brand or at the tracks.
- AAC encoders add a short run of priming samples before the real audio. Players that do not account for it report a slightly longer duration and leave a gap between tracks that should join seamlessly.
- Three media types are in circulation: audio/mp4, audio/x-m4a and audio/m4a. Browsers send different ones for the same file.
Strengths of M4A
- Better sound than MP3 at the same bit rate.
- An index in the file gives exact duration and fast seeking.
Limitations of M4A
- Shares its container with video, which confuses type detection.
- Three media types are in circulation for the same file.
Typical uses of M4A test files
- Testing audio uploads from iPhones, which record voice memos as M4A
- Checking podcast and audiobook pipelines
- Verifying type detection between audio and video MP4
- Testing transcoding to MP3 or Opus
Software that opens M4A
- Apple Music, iTunes and QuickTime Player
- Chrome, Firefox, Safari and Edge
- VLC and Windows Media Player
- Android and iOS, natively
- FFmpeg and MP4Box
Specifications
Related
M4A sample files: questions
- Which codec do the M4A samples use?
- AAC-LC at 128 kbit/s, 44,100 Hz stereo, which is the combination every device and browser plays.
- Is an M4A file the same as an AAC file?
- Not quite. M4A is AAC inside an MP4 container, with an index that allows seeking. A file ending in .aac is a bare stream of AAC frames with a small header on each and no index.
- What is the MIME type of an M4A file?
- The MIME type is audio/mp4. You will also meet audio/x-m4a and audio/m4a in practice. The file extension is .m4a.
- Is a sample M4A file the same as a dummy or example M4A file?
- Yes. Sample, test, dummy and example M4A files are different names for the same thing: an M4A file with known contents that stands in for a real one. Any file on this page will do wherever a tutorial or a test plan asks for a dummy M4A file.