Disclaimer: This post may contain affiliate links, meaning we get a small commission if you make a purchase through our links, at no cost to you. For more information, please visit our Disclaimer Page.

File compression or decompression are both important processes in today’s modern computing world. Businesses need to share data with each other to get things done, and large documents, graphically heavy files, and other important details take up a lot of space.

Sending, receiving, and downloading these types of files could take a long time, slowing down business operations all over. In order to mitigate this issue, file compression applications like WinZip come into play. They will keep all of the data in a particular file, compress it down to a smaller size, make it easier to send along to its destination, and then unpack it back to its original size.

However, there might be occasions where users notice that the program unzips files quite slowly. We can address situations in which this might occur, go over anything someone might be able to do in order to speed up the process, and talk about which factors might play into the unzipping speed overall.

Additionally, we will talk more about file compression, including reducing the size of a compressed file further and some possible reasons why said file might remain bigger than it should be.

Why Does WinZip Unzip Files So Slowly?

There can be a few common reasons why WinZip might unzip files slowly on your system. In fact, before we get into any reasons that could be specific to the program, we should address the system itself.

While some compression software can work differently or better than their counterparts, it is also true that your computer’s specs can play a role in how fast this all goes. We will cover this in greater detail in a later section as we talk about what things affect unzip speed, but it is important to know that some of the limitations here may be on your system.

That said, there could be some possible tweaks to your system that might help you speed up this process.

The other reason has to do with processes that WinZip itself may need to go through. These could be related to file scanning, file size, and what kind of storage unit you’re using to keep or move the file. Similarly, the file system on Windows itself has some impact on the speed with which files can be compressed or extracted.

This isn’t specific to WinZip itself, and other extractor programs will face the same limitations. However, it could be more noticeable on a program like WinZip, and there are alternative applications that don’t seem to suffer some kind of sluggish effect as much as WinZip might.

How Do I Unzip Files Faster?

We’ve touched on some of the aspects that might make WinZip perform at suboptimal speeds. Fortunately, there might be a few things that you can do in order to expedite this process.

Our list isn’t necessarily comprehensive, and some of the things you can do may depend on which systems you are running. Background processes can also influence things. However, we can provide some of the broader troubleshooting solutions that many users may find helpful.

1. Temporarily deactivating your antivirus software may help to speed things up here. Depending on the settings for your antivirus, it could be trying to scan the file as it is extracting it, preventing it from moving quickly.

Sometimes, it may try to scan the file at the beginning, holding it until you restart the program. If you do turn this feature off for the extraction process, we recommend that you scan the file or files manually right after you’ve extracted them. It is good to take this precaution, just to be on the safe side.

2. Use as much RAM as possible. This is particularly important if the file you want to extract is very large. Even being able to increase your RAM from 8 gigabytes to 16 can improve things dramatically on this front.

3. If you have a second drive available that you can plug in, do so for the extraction part of the process. If you are extracting files from a zipped archive to the same drive on which the archive is stored, the process will slow down.

Here, the drive has to bounce between reading the archive and writing the files that it is extracting for you, making the process much more sluggish than it could be with multiple drives at your disposal.

4. Other than these fixes, it is good to keep in mind that there aren’t many ways to increase unzipping speed for large files.

For big files that use multiple gigabytes of space, the hardware you are running has a larger impact on extraction speeds than the program you’re using in order to do it.

What Affects Unzip Speed?

Although we’ve touched on some of the ways you might add a little speed to WinZip’s own decompression process, the limits of your system also have some impact on this measurement. Before we get into that, we should cover the Windows Attachment Manager Service first. This process can slow down a lot of what WinZip does.

It usually comes into play when you download files from the web, including those that you might receive for work via your email address. For our purposes, we will assume that you’re dealing with a file like this, and you need to put it on your system as an archive before you can start the extraction of its contents.

When you receive an archive of files in this way, the service we mentioned above will, in most cases, create an alternate data stream based on the NTFS file system, and it will do so specifically for this archive. Once done, this stream includes information about the internet zone, which is how the application knows what to do with the file.

In short, it uses this information in order to determine if it needs to block the file, give you access with appropriate warnings, or just let it through altogether.

Compressed files with the .zip extension are not usually something that Windows will consider high-risk. That said, the contents of a zipped archive could be riskier than the container in which they are kept.

Because WinZip knows about Attachment Manager, it communicates with this application in order to share information about the files inside the archive. This subjects the archive, and WinZip, to extra processing time, all of which can slow down how fast the program operates.

In any .zip file’s properties, you can choose to ‘Unblock’ the archive itself. Doing so will cut the Attachment Manager out of the process, and it could speed up the extraction.

In your system, the processor you have can make a big difference in how fast extraction can happen. The processor’s speed determines how quickly it can read and transfer data to the drive for you. A faster CPU can help with this.

However, it may be most noticeable only when you’re dealing with large files. These are the ones that will seem like they extract the slowest, and better processing speeds might help them.

Also, the type of drive you use can have some impact here. The hard drive also reads and writes at particular speeds. Its maximum speed will determine at least part of how quickly the decompression process happens. On a related note, solid-state drives can read and write this data faster than their magnetic cousins.

If you deal with very large archives on a regular basis and have access to an SSD, it may be best to use this sort of drive for this activity. This is particularly true if you are able to use a second drive to write the extracted files to the SSD.

Does Compressing a File Make It Smaller?

Yes, compressing a file reduces its size on the disk. Precisely how much the file size will shrink may depend upon what type of data you’re trying to deal with in the archive itself.

Additionally, it doesn’t make files smaller. It helps them to take up less space on whatever storage unit you are using. It’s also worth noting that .zip archives will compress each file separately, and group compression may see better rates of space-saving sizes once everything is done.

How Do I Reduce the Size of a Zip File?

Although it is possible, it can be difficult to reduce the size of a file that is already zipped up. Zip is an old compression format, and it may not compress files as well as some of its newer cousins. Additionally, some types of data lend themselves to compression at better rates than others.

Some audio or image formats, for example, are already heavily compressed, and you may not get much out of zipping them up. Furthermore, you can’t zip up a zipped file again and expect it to get smaller. In some cases, this can increase the file size instead.

For the best results, it is a good idea to familiarize yourself with which files are lossless when they are unzipped. It is these files that could benefit the most from space reduction.

Why Is My Compressed File Still Big?

Some files can’t be compressed in such a way that the space they use is reduced significantly. In most cases, this is because the file type you’re working with is compressed as much as it can be before you even zip it up. In others, you may just have a very large uncompressed file that is still somewhat large when you compress it.


WinZip is one of the older compression forms that you’ll see, but it is still popular today due to its simplicity and name recognition. If you have many small files you want to compress, WinZip should suffice. For larger files on older machines, it might seem slow or cumbersome, but there are things you might be able to tweak to speed it up.