7Z MIME Type

About 7-Zip archive files

7-Zip’s format usually compresses better than ZIP, but neither Windows Explorer (before Windows 11’s 2023 updates) nor macOS Finder could open it out of the box. For files meant for anyone, ZIP is the safer choice.

File signature

7Z files start with 37 7A BC AF 27 1C ("7z\xBC\xAF\x27\x1C"). The extension and the type a browser reports for an upload both come from the file name, so check these bytes on the server before trusting a file.

Serve .7z with the right Content-Type

Content-Type: application/x-7z-compressed

application/x-7z-compressed 7z;

AddType application/x-7z-compressed .7z

@7z path *.7z
header @7z Content-Type "application/x-7z-compressed"

curl -sI https://example.com/file.7z | grep -i '^content-type'
# Content-Type: application/x-7z-compressed

Set the type in code

res.set('Content-Type', 'application/x-7z-compressed');
// Or make the browser download it:
res.attachment('file.7z');

import mimetypes

mimetypes.add_type('application/x-7z-compressed', '.7z')  # if your system doesn't know it
mimetypes.guess_type('file.7z')[0]  # 'application/x-7z-compressed'

mime.AddExtensionType(".7z", "application/x-7z-compressed")
w.Header().Set("Content-Type", "application/x-7z-compressed")

Accept .7z uploads

<input type="file" accept=".7z,application/x-7z-compressed">

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
• .rar (application/vnd.rar): RAR archive
• .gz (application/gzip): Gzip file

More archives

.tar . Look up any extension or type with the MIME type lookup.

Sources

• IANA Media Types registry (not listed)
• MDN: Common media types

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Frequently asked questions