File Compression: Everything You Need to Know
About Compressing Files & Why

How & Why File Compression Can Save You Time, Money, and Hassle Today

If you've ever downloaded something from the Internet (which is pretty likely given the fact that it's 2017), there's a good chance you've come across ZIP files, (or some other type of file compression like RAR or 7Z).

There's also a good chance you're not entirely sure how file compression works, which would explain why you're reading this post.

Out of the hundreds of different types of file extensions, compression files like ZIP are unique. They aren't designated to images, video, audio, or any one type of data.


But wait, how can you reduce the size of a file without ruining the data? It might sound impossible, but once you know what's going on behind the scenes, it makes a lot of sense.

So if you have ever wondered "what does compressing a file do?" then you are in the right place. So, let's get started with some of the basics.

File Compression Image

What is file compression?

It's true that ZIP isn't the only type of compressed file, but it's definitely one of the most common. We could go on and on about ZIP, ARC, ARJ, RAR, CAB, and the dozens of others, but they all essentially function the same way. So, for the purpose of keeping this post clear and easy to follow, we'll be focusing on just the ZIP extension.

Essentially, a compressed file is a sort of archive that contains one or more files that have been reduced in size. Since these file are smaller, they can be stored without taking up much space, or transferred at higher speeds over the Internet. By using a program such as WinZip, you can then decompress the file or files back into their original state without any degradation.

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Still unsure how this wizardry actually works? Bear with me while I get a little more technical.

How does file compression work?

Here's where things can get a little complicated. Essentially, there are two main types of file compression ? lossless and lossy. Lossless compression takes your files and reduces their size without losing any information. Lossy compression reduces your file size by chopping off bits and pieces that aren't 100% necessary to function. I know that's a pretty big oversimplification, so let's break them down one at a time.

Lossless file compression

This may sound crazy, but it's how it works. In order for lossless compression to work, a file needs to be reduced without losing anything. This is done by removing redundancy.

File compressors remove redundancy

What's redundancy, you ask?

Data redundancy is a condition created within a database or data storage environment in which the same piece of data is held in multiple places.

By eliminating redundancy, you are left with just one instance of each bit of data.

Lossless file compression would be like taking this:


and compressing it to this:


The same information is there, but it's simplified to takes up less space (Note that the numbers correspond to the number of times that the previous letter repeats). This way, when you decompress (unzip/open/extract) the file, it knows how to go back to its original form. This is mainly used for text and spreadsheets because losing words or data from a document isn't something you want to happen.

Lossy file compression

Lossy compression functions basically the same way, but as you can probably tell by the name, it results in some data being permanently lost (not as bad as it sounds).

This is more common with media files like video, audio, and images because they don't really suffer too much from the data loss. In fact, music and videos you currently have on your computer have probably been compressed and you don't even notice the missing bits. This is because the data that's removed is outside of the range humans can hear or see.

There is a downside, however - If you compress the same file over and over again using the lossy method, you'll start to notice a reduction in quality since data is being removed each time.

Why bother compressing your files?

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If you're someone who frequently edits media files, you know how crucial file compression is when transferring photos, music, and videos. You really don't want to kill all your bandwidth and waste tons of valuable storage space. If you're not one of those people, then here's why it's so necessary.

Compress files for faster transfer

Takes up less space

Let's say you have a huge number of files on your computer, but don't plan on doing anything with them for a while (maybe you're a virtual hoarder, who knows). Leaving them on your hard drive to take up space isn't the most practical thing to do.

Instead, you can ZIP a large quantity of files into a single archival folder that both frees up space and makes organizing a lot cleaner.

Storing your collection of old Kung Fu movies on a hard drive? Compress them all down into one ZIP file and be amazed at how much space you'll save.

More efficient transfers

If you've ever tried emailing a really large file, you know it can take a long time. Even worse - trying to email several documents at once. A lot of the time your message will fail because some email clients don't allow files over a certain size to transfer.

Sure, you could send a series of multiple emails with small attachments on each, but that's both time consuming and hard to keep track of (and you'll probably annoy the recipient).

By compressing your documents into one ZIP file, it will take up less space and transfer a lot faster. The recipient just needs to use a program like WinZip to extract the files and they'll have everything you sent them in one, organized folder.

Can save money

Hard drives are expensive - I don't have to tell you that. Storing loads and loads of data obviously takes up tons of space, so why not get the most bang for your buck?

File Compression can save you money

Say you have 200GB of data you need to stash away on your computer, but your hard drive is only 250GB. Sure it will fit, but then you're left with only 50GB which isn't much these days.

You could go out and buy a larger, more expensive hard drive, transfer everything from the old one to the new one, and be good to go.


You could compress your 200GB of data into a ZIP file that only takes up 100GB. You still have all of your files, ready to use when you need them, but you don't have to spend any money on more storage space.

How to compress/decompress files

At this point, you should have a pretty solid understanding of file compression - how it works and why it's beneficial. That's great and all, but you probably want to know how to zip and unzip files yourself, right?

The following is a crash course on the process of compressing and decompressing files. Luckily, if the files you're trying to compress are relatively small, your operating system should be able to zip them without the need of 3rd party software. A simple right click option will take care of it for you.

But what if you're dealing with several gigs of data? You're going to need something with more "oomph" to take care of things. Lucky for you WinZip is a leading file compressor.

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Compressing large files within WinZip

  1. This part's pretty tricky. First, you need to open WinZip (hard, right?).
  2. Then you need to find and select all the files you want to compress in the Files pane.
  3. Once they're all selected, you'll click Add to Zip.
  4. Click Save as.
  5. Select a target location, give it a name, and click Save. And that's all there is to it.

Compressing large files outside of WinZip (you need WinZip installed for this to work)

  1. Open a folder containing all the files you wish to compress.
  2. Highlight each one you're going to zip.
  3. Right click in the highlighted area and the WinZip submenu will appear. You have a couple options to choose from here.
  4. * Add to Zip file: clicking this option lets you name your Zip file, determine how it should be compressed, and add encryption.

    * Add to [filename].zip: This options is much quicker, but you don't have as much freedom. It will essentially create a Zip file with the name of the containing folder, but you won't be able to customize the settings.

  5. Your Zip file is now created for you to store or transfer.
Unzip compressed files

Decompressing (unzipping) your files

Unzipping a file is as simple as either:

  1. Dragging the file or folder from the zipped folder to a new location.


  1. Right click inside the zipped folder, select Extract All, then follow the prompts.

There you have it

So, that about sums up the basics of file compression. It sounds impossible being able to reduce the size of a file, then put it back together in another location, but that's essentially what happens.

If you're interested in learning more, check out WinZip's website for more documentation.

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