BIN MIME Type

About Binary data files

The “I don’t know what this is” type. Browsers always download it rather than display it, so it is also used to force a download. Servers send it for any extension missing from their MIME table, which is the usual reason a .mjs, .wasm or .webmanifest file doesn’t work: add the mapping for that extension.

File signature

BIN has no fixed signature: it is data without a magic number, so validate uploads by parsing the content rather than by checking bytes.

Serve .bin with the right Content-Type

Content-Type: application/octet-stream

application/octet-stream bin;

AddType application/octet-stream .bin

@bin path *.bin
header @bin Content-Type "application/octet-stream"

curl -sI https://example.com/file.bin | grep -i '^content-type'
# Content-Type: application/octet-stream

Set the type in code

res.set('Content-Type', 'application/octet-stream');
// Or make the browser download it:
res.attachment('file.bin');

import mimetypes

mimetypes.add_type('application/octet-stream', '.bin')  # if your system doesn't know it
mimetypes.guess_type('file.bin')[0]  # 'application/octet-stream'

mime.AddExtensionType(".bin", "application/octet-stream")
w.Header().Set("Content-Type", "application/octet-stream")

Accept .bin uploads

<input type="file" accept=".bin,application/octet-stream">

The accept attribute only filters the file picker; users can still choose another file. Listing the extension as well as the type matters, because operating systems don’t always report the type you expect.

Related types

• .zip (application/zip): ZIP archive
• .exe (application/vnd.microsoft.portable-executable): Windows executable
• .wasm (application/wasm): WebAssembly module

More programs and binaries

.apk , .jar . Look up any extension or type with the MIME type lookup.

Sources

• IANA registration: application/octet-stream
• MDN: Common media types

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Frequently asked questions