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What file formats of compressed archives does Windows 10 natively know how to work with on fresh install?

There are many file formats for compressed archives. To name a few:

  1. .tar.gz
  2. .zip
  3. .rar
  4. .7z
  5. etc

But I'm especially curious what is the subset of these various "compressed archive" file formats that Microsoft Windows natively knows how to decompress out-of-the-box after a fresh install of the OS -- without having to install additional software.

Which compressed archive file formats does Windows 10 know about on fresh install?

Michael Altfield
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    Related question [here](https://superuser.com/questions/894859). Answer: Deflate and Deflate64 (this functionality hasn’t been changed since it was introduced). Deflate is the same compression that .zip files support. [Background](https://superuser.com/questions/575840) – Ramhound Sep 20 '21 at 21:55
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    If you wish to provide compressed files for Windows, you might also ask *what versions/types* of these archive formats? For example, can MS Windows natively open a *pasword-protected* Zip, and with what encryption method (e.g., AES-256, ZipCrypto)? It would be nice to have those specifications, though I've not seen such documentation. BTW, include CAB, XPRES*n*K and LZH as native Windows compressed formats. See https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/compact . – DrMoishe Pippik Sep 20 '21 at 22:01
  • The only third party de-compression W10 supports is ZIP, you will have to use 7-zip to do most others. – Moab Sep 21 '21 at 00:18
  • “can MS Windows natively open a pasword-protected Zip, and with what encryption method (e.g., AES-256, ZipCrypto)?” - No – Ramhound Sep 21 '21 at 00:46

1 Answers1

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Windows 10 knows only about ZIP archive files; it can create them, and open them. It can't create encrypted ZIP files; it can open them if and only if encrypted using very insecure ZipCrypto encryption (not the default with 3rd-party archivers such as WinRAR and 7-Zip, but can usually be selected as an option). The only way to send a user of native Windows without 3rd-party archiver support an encrypted file is to risk ZipCrypto. (A self-extracting file using any format will work, but email usually objects to executables.) This for Windows 10, last tried in 2021; later versions may extend support.

pol098
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  • This claim is wrong. For instance, `.cab` files are another (obscure) archive format natively supported by Windows. `.cab` files support DEFALTE and LZX (a variation of the LZ77 family) which should give a bit better compression ratios ([source link](https://learn.microsoft.com/en-us/previous-versions/bb417343(v=msdn.10)#microsoft-lzx-data-compression-format)). – Socowi Feb 08 '23 at 13:00
  • Not sure if there are other hidden formats. At least theoretically speaking, Windows supports decompressing gzip and brotli too, because it comes with a pre-installed browser (*Edge*) which sends the user agent `ACCEPT-ENCODING: gzip, deflate, br`. Whether or not that functionality is accessible to end users for decompression file archives (e.g. an uncompressed `.zip` or `.cab` archive) is another question. – Socowi Feb 08 '23 at 15:09
  • Thanks to *Socowi* for details re my comment. The question I was really answering (not exactly what was asked) was "how can I send an encrypted file to a naïve user of Windows without a 3rd-party archiving program", which I have had to do. My point is that you *can* do this, but only if you take the steps to use the not very secure ZipCrypto encryption (7-Zip and WinRar both support it, possibly with a different name, and not as default, must select it). This is correct (unless changed in a later Windows) - I did it, a couple of years ago. – pol098 Feb 09 '23 at 18:02
  • Thanks for clarifying this. OP never mentioned encryption, so I already wondered about that part of your answer. – Socowi Feb 09 '23 at 18:22