ZIP Files Unpacked: A History of Data Compression's MVP

ZIP files have an interesting and grim past. There’s more to know about his humble file utility than most people imagine.

In the past, I paid little attention to home storage solutions. Don't get me wrong, my home was always neat and in order, but it could have been more efficient. I've always had a thing for how dumb late-night commercials and their gimmicky products were. So it was a surprise one day when my wife brought home one of these.

A person vacuum-seals clothes in a transparent storage bag on a wooden table.

It's just a humble vacuum storage bag. However, it reminded me of one of those infomercials from the Shamwow guy or Billy Mays. So I turned up my nose and let her continue with her folly.

To my chagrin, these things worked great. They compressed a huge amount of out-of-season clothing into a few thin packages that slid neatly under the bed. Boom, tons of space cleaned up on the closet shelves.

My snobbery had gotten the better of me. I should have known this was possible. Compression is a simple concept we use every single day in computer science. Embodied most prominently in the humble ZIP file, we all take compression for granted. It may be time to stop turning up our noses at such a mundane thing and take a look under the hood a little more often.

Let's put aside our assumptions and start with a concise description.

What Exactly Is a ZIP File?

A ZIP file is a compressed file format that reduces the size of files and folders using lossless data compression algorithms. It allows multiple files and directories to be bundled into one file, making transporting, sharing, and storing easier. ZIP files not only decrease file size to save storage space but also enable faster file transfer over the internet or between devices. Various software programs can create and extract them, and they support encryption and password protection for secure file sharing.

The History and Evolution of ZIP Files

In the early days of computing, storage space, and bandwidth were at a premium. Computers had limited storage capacity, and internet connections were slow. Transmitting large files over networks was time-consuming, and using disk space as efficiently as possible was crucial. This environment set the stage for the development of file compression techniques, which aimed to reduce file sizes, making them easier to store and faster to transmit.

The ZIP file format eventually claimed the compression crown, but not without a fight. Its origin story is contentious and grim, with legal disputes and controversies involving the ARC compression format and its creator. 

This video covers the compelling story of Phil Katz, ARC, and everyone involved in the birth of the ZIP file format quite well. I recommend watching it if you have time. 

Despite the controversies, Katz became the face of compression technologies during this era. The ZIP format itself evolved to include more robust encryption, support for larger files, and improved algorithms, maintaining its relevance and utility. 

How ZIP Files Work

ZIP files shrink files without losing any information using lossless compression. This type of compression works by finding repetitive information in a file and replacing it with shorter codes. If you have a book with repeating sentences, you note where they repeat instead of writing them every time. Voilà - smaller files, and when you need the originals, it rebuilds them perfectly using these codes. 

ZIP files can also combine many files and folders into one big file. This consolidation makes it easier to organize and share lots of data at once, like sending a whole project's files in one go instead of one by one.

When making a ZIP file, you can choose how much you want to compress it. More compression makes files smaller but takes longer to compress. Lighter compression settings are faster but produce larger files than heavier compression.

The Importance of ZIP Files in Everyday Tech

ZIP files are super useful in our tech-filled lives. They help in many ways, like when companies send out new software. Instead of downloading many files, you get one ZIP file with everything inside. ZIP files are also excellent for managing email attachments. Since email providers often have size limits, compressing files into a ZIP can help keep the size under the limit, making it possible to send them.

Because ZIP files make files smaller, they speed up sending and receiving data online. That is a big deal for websites that need to load fast or when you're sharing big files with friends. By compressing data, ZIP files also help manage storage better, whether on your phone, computer or in the cloud. You can keep more of what you want without running out of space.

From family and friends to big companies, ZIP files are at the core of how everyone uses computers. They make it easier to handle lots of data, share it quickly, and save space.

Security and ZIP Files

ZIP files aren't just about making files smaller; they also offer ways to keep your data safe. When you create a ZIP file, you can add encryption, which is handy when sending important stuff over the internet that needs a little privacy.

However, just like any security measure, there can be weaknesses. For example, if someone figures out your password, they can get into your ZIP file. To keep your data safe, always use strong, hard-to-guess passwords and consider using more advanced encryption algorithms like AES-256 if they're available. Taking these steps makes it much harder for anyone to sneak a peek at anything compromising.

Practical Tips for Using ZIP Files

Creating ZIP Files:

  • On Windows:
    1. Right-click on the file or folder you want to compress.
    2. Select "Send to" and then "Compressed (zipped) folder."
    3. Name your ZIP file and press Enter.
  • On Mac:
    1. Right-click on the file or folder.
    2. Choose "Compress [name of file or folder]."
    3. Your ZIP file appears in the same location.

Extracting ZIP Files:

  • On Windows:
    1. Right-click the ZIP file.
    2. Choose "Extract All" and then follow the instructions.
  • On Mac:
    1. Double-click the ZIP file.
    2. Files automatically expand and appear next to the original ZIP file.

Organizing Files for Compression:

  • Group related files together in a folder before zipping.
  • Remove any files you don't need to compress. The fewer files you zip, the quicker the process

Managing Large ZIP Archives:

  • Label your ZIP files clearly with dates or project names so you know what's inside without opening them.
  • Check your large ZIP files periodically to ensure they open correctly. This will help you catch any potential data corruption early.
  • Use reliable software for ZIP files that supports error checking and repair to maintain data integrity.

Encrypting ZIP Files

Given that major operating systems lack built-in support for robust encryption in ZIP files, we recommend 7-Zip for encryption needs across all platforms. 7-Zip, a free and open-source file archiver, supports AES-256 encryption for ZIP files. Though 7-Zip is native to Windows, Mac and Linux users can install the command-line version, ensuring consistent encryption capabilities across different systems.

Installing 7-Zip:

You can download all the flavors of 7-Zip at:

  • Windows: Download 7-Zip from its official website and install it as usual.
  • Mac/Linux: Download the 7-Zip command-line version. Move the downloaded 7zz binary to /usr/local/bin to make it accessible system-wide. This may require administrator permissions.

Encrypting ZIP Files:

Common Steps for All Platforms:

  • Open Your Terminal or Command Prompt:
    • Windows: Press Win + R, type cmd, and press Enter.
    • Mac/Linux: Open Terminal from your applications or search for it.
  • Navigate to Your Files:
    • Use the cd command to change to the directory containing the files you want to compress and encrypt.
  • Encrypt and Compress:
    • Execute the following command, substituting for your desired ZIP file name, yourfolder for the folder or files you're compressing. Be sure to replace PASSWORD with your actual password.

Windows Command:

7z a -tzip -pPASSWORD -mem=AES256 yourfolder/

Mac/Linux Command:

7zz a -tzip -pPASSWORD -mem=AES256 yourfolder/

Best Practices for Encryption:

  • Strong Passwords: Use a complex, unique password to secure your ZIP file. This enhances security and makes it difficult for unauthorized users to access your data.
  • Password Management: Keep your password in a secure location. If you lose it, there is no way to recover the encrypted files.
  • Compatibility Check: Ensure recipients of your encrypted ZIP file can use 7-Zip or compatible software to decrypt the file. Sharing the encryption method and password securely is also essential.

Using 7-Zip to encrypt your ZIP files on any operating system provides a reliable method for protecting sensitive data. With its support for AES-256 encryption, 7-Zip offers a high level of security for your files, whether you're archiving personal data or sharing confidential information.

Photo by Timur Weber on Pexels

Cover Photo by Nina Cuk on Unsplash

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