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

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Type: application/octet-stream
SHA-256: 3703a79acd8c1f6042a0b6d4c9e2e8b6ae69df5889475a6cde52c5a7b813f95d
Direct URL: https://sampletestfiles.com/downloads/bin/sample-bin-20mb.bin

What is in this file

20,971,520 pseudo-random bytes from a seeded generator, so every build 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  41 f8 6e 7b 20 a4 36 0b f3 6c 18 20 bb 2f 08 fd  |A.n{ .6..l. ./..|
00000010  4a c8 b2 38 c1 f3 9b b1 88 fc c9 ca 46 cd 2d 0a  |J..8........F.-.|
00000020  fb fa 36 57 a0 94 0a d2 9d 12 23 0b b8 15 6a aa  |..6W......#...j.|
00000030  68 9f 86 52 e0 6c 54 20 79 a4 f2 52 5b af d4 ff  |h..R.lT y..R[...|

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 download and upload throughput
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	3703a79acd8c1f6042a0b6d4c9e2e8b6ae69df5889475a6cde52c5a7b813f95d
Created	2026-10-10
Validation	Exact size, signature bytes and structure checked when the file was generated
Preview	Not available for this file; details only
Source	Generated for this site; 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

Download from the command line and verify

Fetch the file with curl, then compare its checksum with the SHA-256 value above.

curl -o sample-bin-20mb.bin 'https://sampletestfiles.com/downloads/bin/sample-bin-20mb.bin'
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. A matching value proves that the download is complete and unaltered.

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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