25 KB M4A sample
An M4A file of exactly 25,600 bytes. It is a valid MPEG-4 audio file, generated by this site. Compare its checksum and test it with the parser used by your application. Use it wherever you need a 25 KB sample, test or dummy M4A file.
Download
sample-m4a-25kb.m4a
25 KB25,600 bytes
Download 25 KB M4ACreated in your browser in a few seconds, then checked against the SHA-256 checksum. The file is not uploaded anywhere. No sign-up.
- Type
- audio/mp4
- SHA-256
e328327ef8ca2e0c57a7d1b5cea07dee5b2882cbcf50761e8f688aec6cf25a9f- Delivery
- Created in your browser from static generator assets (how it works).
What is in this file
68 AAC frames (1.6 s) of a synthesised musical phrase that repeats every eight seconds, in one audio track. 119 bytes of a trailing "free" box bring the file to the exact size.
| Duration | 1.6 s |
|---|---|
| Audio codec | AAC-LC |
| Bit rate | 128 kbit/s |
| Sample rate | 44,100 Hz |
| Channels | Stereo |
| Container | MPEG-4 (brand "M4A ") |
| Fast start | Yes (moov before mdat) |
First bytes of the file
The first 64 bytes of sample-m4a-25kb.m4a as a hex dump: offset, bytes, then the same bytes as text. The M4A signature is 66 74 79 70 4D 34 41 20 at offset 4.
00000000 00 00 00 1c 66 74 79 70 4d 34 41 20 00 00 02 00 |....ftypM4A ....|
00000010 4d 34 41 20 6d 70 34 32 69 73 6f 6d 00 00 03 48 |M4A mp42isom...H|
00000020 6d 6f 6f 76 00 00 00 6c 6d 76 68 64 00 00 00 00 |moov...lmvhd....|
00000030 e5 7b 69 80 e5 7b 69 80 00 00 03 e8 00 00 06 2b |.{i..{i........+|Preview
Creates the file in your browser and shows it here.
Where 25 KB matters
A 25,600-byte file: the size of a small web image or a short document. These are the default limits a file of this size is useful for testing:
| System | Limit | Note |
|---|---|---|
| TCP initial congestion window | About 14.6 KB (10 segments) | 25 KB needs at least two flights of packets on a new connection. |
| Base64 encoding | Adds 33 percent | A 25 KB file becomes about 34 KB inside JSON or an email. |
Use this file for
- Checking email size handling
- Checking podcast and audiobook pipelines
- Verifying type detection between audio and video MP4
Testing notes for M4A
- Three media types are in circulation: audio/mp4, audio/x-m4a and audio/m4a. Browsers send different ones for the same file.
- 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.
Technical details
| File name | sample-m4a-25kb.m4a |
|---|---|
| Format | M4A (MPEG-4 audio) |
| Extension | .m4a |
| MIME type | audio/mp4 |
| Size | 25,600 bytes (25 KB) |
| Kind | Binary |
| Signature | 66 74 79 70 4D 34 41 20 at offset 4 |
| SHA-256 | e328327ef8ca2e0c57a7d1b5cea07dee5b2882cbcf50761e8f688aec6cf25a9f |
| Created | 2026-10-23 |
| Validation | See the listed size and SHA-256. Small downloads are checked in the browser; verify streamed downloads manually. A hash match does not prove parser compatibility. |
| Preview | Available on this page |
| Source | Generated in your browser by this site's generator; not copied from elsewhere |
| Licence | Free to use, modify and redistribute (terms) |
| Category | Audio |
Check the stated structure and checksum against your application requirements. As with any download, scan the file with your own security tools before opening it. How files are made and checked
Verify your copy
This file is created in your browser, so it has no direct URL for curl or wget. The generator is designed to produce reproducible bytes. After saving, compare the checksum with the SHA-256 value above.
sha256sum sample-m4a-25kb.m4a # Linux
shasum -a 256 sample-m4a-25kb.m4a # macOSOn Windows, run Get-FileHash sample-m4a-25kb.m4a -Algorithm SHA256 in PowerShell. For scripts and pipelines, save the file once and keep your own copy.
Related files
Questions about this file
- Is this file exactly 25 KB?
- Yes. It is 25,600 bytes, which is 25 KB in the binary units that operating systems and server limits use (1 KB = 1,024 bytes).
- What is inside the 25 KB M4A file?
- 68 AAC frames (1.6 s) of a synthesised musical phrase that repeats every eight seconds, in one audio track. 119 bytes of a trailing "free" box bring the file to the exact size.
- 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.