20 MB MKV sample
An MKV file of exactly 20,971,520 bytes. It is a valid Matroska video file, generated by this site. Compare its checksum and test it with the parser used by your application. Use it wherever you need a 20 MB sample, test or dummy MKV file.
Download
sample-mkv-20mb.mkv
20 MB20,971,520 bytes
Download 20 MB MKVCreated in your browser in a few seconds, then checked against the SHA-256 checksum. No sign-up.
- Type
- video/x-matroska
- SHA-256
2d69dbc37d66c9be1a83c5d26df2d845fe81b2c02d2c69ecf7243bbcd86d9943- Delivery
- Created in your browser from static generator assets (how it works).
What is in this file
11,160 frames (6 min 12 s) of a synthetic test pattern with a frame counter, looping every six seconds, in one H.264 (AVC) video track. The index of key frames comes before the picture data, so a player can seek without reading the whole file. 52 bytes of an EBML Void element bring the file to the exact size.
| Dimensions | 640 × 360 px |
|---|---|
| Duration | 6 min 12 s |
| Frame rate | 30 fps |
| Video codec | H.264 (AVC), Main profile |
| Audio | No audio track |
| Document type | matroska |
| Clusters | 372, one for each key frame |
| Seek index | Cues element before the first cluster |
First bytes of the file
The first 64 bytes of sample-mkv-20mb.mkv as a hex dump: offset, bytes, then the same bytes as text. The MKV signature is 1A 45 DF A3.
00000000 1a 45 df a3 a3 42 86 81 01 42 f7 81 01 42 f2 81 |.E...B...B...B..|
00000010 04 42 f3 81 08 42 82 88 6d 61 74 72 6f 73 6b 61 |.B...B..matroska|
00000020 42 87 81 04 42 85 81 02 18 53 80 67 01 00 00 00 |B...B....S.g....|
00000030 01 3f ff cc 11 4d 9b 74 b3 4d bb 8e 53 ab 84 15 |.?...M.t.M..S...|Preview
MKV files cannot be shown in a browser. Download the file and open it in an application that reads MKV, such as VLC and mpv.
Where 20 MB matters
A 20,971,520-byte file: right at the default attachment limit of Outlook, and just under the 25 MB ceilings of Gmail and GitHub web uploads. These are the default limits a file of this size is useful for testing:
| System | Limit | Note |
|---|---|---|
| Microsoft Outlook | 20 MB of attachments by default for internet mail accounts | This file is right at the limit; add a second attachment and it is exceeded. |
| Gmail | 25 MB per message | Under the limit, although email encoding adds about a third in transit. |
| GitHub web uploads | 25 MiB per file added through the browser | Accepted. Pushing with Git allows larger files. |
| Cloudflare Pages assets | 25 MiB per file | The largest round size that can be served as a static asset. |
| Amazon API Gateway | 10 MB payload | Rejected; the upload has to go directly to object storage. |
| ASP.NET Core (Kestrel) | About 28.6 MB request body by default | Accepted with room for the multipart overhead. |
Use this file for
- Testing image resizing and memory use
- Verifying type detection between MKV and WebM
- Testing media servers and players with a seekable file
Testing notes for MKV
- Safari and Firefox do not play MKV, and Chrome does so only for some codecs. Remux to MP4 or WebM before showing video in a page.
- A file with no Cues element still plays but cannot seek quickly. Recordings that were interrupted, and live captures, are often like this.
Technical details
| File name | sample-mkv-20mb.mkv |
|---|---|
| Format | MKV (Matroska video) |
| Extension | .mkv |
| MIME type | video/x-matroska |
| Size | 20,971,520 bytes (20 MB) |
| Kind | Binary |
| Signature | 1A 45 DF A3 |
| SHA-256 | 2d69dbc37d66c9be1a83c5d26df2d845fe81b2c02d2c69ecf7243bbcd86d9943 |
| 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 | Not available for this file; details only |
| Source | Generated in your browser by this site's generator; not copied from elsewhere |
| Licence | Free to use, modify and redistribute (terms) |
| Category | Video |
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-mkv-20mb.mkv # Linux
shasum -a 256 sample-mkv-20mb.mkv # macOSOn Windows, run Get-FileHash sample-mkv-20mb.mkv -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 20 MB?
- Yes. It is 20,971,520 bytes, which is 20 MB in the binary units that operating systems and server limits use (1 KB = 1,024 bytes).
- What is inside the 20 MB MKV file?
- 11,160 frames (6 min 12 s) of a synthetic test pattern with a frame counter, looping every six seconds, in one H.264 (AVC) video track. The index of key frames comes before the picture data, so a player can seek without reading the whole file. 52 bytes of an EBML Void element bring the file to the exact size.
- Which codec do the MKV samples use?
- H.264 video at 640 × 360 and 30 frames per second, with no audio track. The index of key frames is at the front of the file.