20 MB BIN sample file

A BIN file of exactly 20,971,520 bytes. It is a valid Binary test file file, generated for this site and checked with an independent parser. Use it wherever you need a 20 MB sample, test or dummy BIN file.

sample-bin-20mb.bin

20 MB20,971,520 bytes

Download 20 MB BIN

Created in your browser in a few seconds, then checked against the SHA-256 checksum. No sign-up.

Type: application/octet-stream
SHA-256: 2792ffecd91282645347730c7ca23ea3bfe0527e396779c947e09e8da5c2ef64
Delivery: Created in your browser. Files of 2 MB and more have no direct URL (why).

What is in this file

20,971,520 pseudo-random bytes from a seeded generator, so every copy of the file is identical and compression cannot shrink it.

Content	Pseudo-random bytes
Compressible	No
Structure	None

First bytes of the file

The first 64 bytes of sample-bin-20mb.bin as a hex dump: offset, bytes, then the same bytes as text.

00000000  da a8 c4 b5 cd 5b 4d 49 fa e3 af f3 83 ed 0c 1a  |.....[MI........|
00000010  3a bc df 60 6f 61 73 a7 fb fc 6d 50 a0 da d0 4e  |:..`oas...mP...N|
00000020  ae c3 8b 8f dd 78 1b 5e 1b 2e 24 ff 41 f2 63 71  |.....x.^..$.A.cq|
00000030  31 c8 22 ac 1b 25 9a 69 bc cd 58 4f b6 f9 89 8c  |1."..%.i..XO....|

Preview

BIN files cannot be shown in a browser. Download the file and open it in an application that reads BIN, such as curl, wget and browser download managers.

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.

All 20 MB sample files

Use this file for

Testing email attachment limits
Measuring upload throughput, and download throughput from your own server
Testing size limits precisely

Testing notes for BIN

A file of zeros, as produced by many quick commands, compresses to almost nothing, which makes transfers look far faster than they are.
Because application/octet-stream says nothing about content, strict upload filters reject these files. That is itself a useful test.

BIN format reference

Technical details

File name	sample-bin-20mb.bin
Format	BIN (Binary test file)
Extension	.bin
MIME type	application/octet-stream
Size	20,971,520 bytes (20 MB)
Kind	Binary
SHA-256	2792ffecd91282645347730c7ca23ea3bfe0527e396779c947e09e8da5c2ef64
Created	2026-10-14
Validation	Exact size, signature bytes and structure checked when the generator was built; your copy is checked against the SHA-256 after it is created
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	Testing

Validated for expected format and integrity. 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 bytes are the same every time and in every browser, so after saving it you can compare its checksum with the SHA-256 value above.

sha256sum sample-bin-20mb.bin     # Linux
shasum -a 256 sample-bin-20mb.bin # macOS

On Windows, run Get-FileHash sample-bin-20mb.bin -Algorithm SHA256 in PowerShell. For scripts and pipelines, save the file once and keep your own copy, or use a 1 MB file, which has a direct URL.

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 BIN file?: 20,971,520 pseudo-random bytes from a seeded generator, so every build of the file is identical and compression cannot shrink it.
Is a .bin sample safe to download?: Yes. It is inert data: random bytes that are not executable and have no structure for any program to interpret.

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