File Types That Are Secretly Just .Zip Files In Disguise

The best kept secret in the world 🤫

Not only interesting, but very useful. Especially for pulling pictures and charts out of Office documents quickly or en masse.

PK3 and PK4 files (used by games like quake 3, star wars Jedi knight Jedi academy, doom 3 and etc) are also just zip files. Wish more games would use standard data compression instead of having to use a tool to manually unpack game archives with a script.

I love how Joe uses AI generated images now instead of stock photos 😂

Epub files can also be renamed as zip then extracted. Or you can also just zip a bunch of pictures and save it as .CBZ (or CBR for RAR’ed files) and voila, you have a lossless container/wrapper for your image files that can be viewed with any comic viewer la Sumatra pdf.

For the exe files, i reckon driver installers are basically always archives extractables with 7-zip. Which is really usefull to get the INF and SYS files alone and not deal with the crappy installers of hardware vendors

Jar files are zip folders that hold special code for the JRE to compile at runtime. The structure is defined by the developer of the specific application. The only standard thing about it is simply that it needs a main.class in the root. Other than that, it's up to the dev to build out the program's file structure.

It's actually a great way to design a file format though, I've done it myself with my own coding. It means you can easily edit the file with third party software, and use existing zip libraries to pack data in and out of the file, and you get compression on top of it. It's a smart way to work.

Now I know why I can open .jar files with 7zip or winrar. It makes sense

I'd love to see you go over files such as .DEB (Debian packages) and AppImage/Flatpak/Snap files as well!

Another example is Apple iPSW files, those are the firmware files for all of Apple’s firmwares. Those are secretly ZIP files as well.

The reason you pack it in a zip file is because every file is compressed separately. This means you can have a metadata file inside the zip and just extract this (probably quite small) text file. With other compression formats you would have to decompress the whole (possibly very large) file first to check some small file within.

If you've ever used Scratch (the programming language), you might know that .SB3 and .SB2 files are also ZIPs. Extracting them actually has a use: checking the size of the project.json file inside (which is limited to 5MB). edit: correct error - .sb files aren't .zips

Interesting. I just knew before about that APKs, ISOs, JARs and some EXEs are Zips. The rest was new for me

As a Linux user, I've been so confused as to why .docx and other ms office xml formats have archive manager assigned as default or one of the programs to open it. I suppose it's because the format isn't native or foss to be properly incorporated that file magic can only recognize the .zip aspect of it.

Many years ago (I won't say how many lest I age myself), an indie game I loved that had a level editor had the fan community asking the dev to support custom player skins in the created levels. I looked into how hard or easy that would be, and that's when I first discovered how incredibly useful it is to just package data, images, etc. into a ZIP file and change the extension to make it look fancier 😂 It's nice to know even the big companies do the same thing and it wasn't a dumb novice-dev idea of mine.

Great niche topic to cover. Most of those do indeed have file headers that begin with PK (Phil Katz). We can see this by opening in a hex editor like HxD, or even Notepad++ (if it's not massive in size). Many Windows executables begin with MZ (Mark Zbikowski) and can also be extracted. Thankfully 7zip makes it quick and easy to check.

If you're using something like 7-Zip, you don't need to rename the file. Changing the extension simply tells the OS's built-in archiving software to decompress the file.

Apple platforms like iOS and macOS also hide folders like that. If you've ever installed anything on a Mac, you might know that the app comes in a .dmg file (similar to .iso) and then you're supposed to drag the [AppName].app file from there to your applications folder and run it by double clicking like an .exe. But it's not actually a file, as if you extract a DMG on Windows, the .app shows up as a folder. Inside, there is a directory called "Contents" and in it are a bunch of resource files alongside a "MacOS" directory that has the main executable.

Ah yes, opening files with a file extractor. I always do this with Android APK files whenever I want to extract some fonts or assets files used in that app. I never knew you can also open Office files the same way, this is helpful.