How to Compress PNG Files Using Windows or OS X

These guides (one for Windows, one for OS X) will show you how to compress .PNG images so the files are smaller in size but no quality is lost to the image itself.

The most common reason for wanting to compress PNG files is so that they can be used on the Internet, and whatever medium it is they’re being served through (a web page, twitter, even Facebook) will load faster – because the files are smaller in size. The additional benefit is that the images themselves will not suffer in quality.

If you have a website, it’s particularly important to compress your image files, as Google is putting more and more weight on ‘page speed’ when it determines where your content ranks in their search results. The smaller your files, the faster your page will load. So lets jump in!

If you’re a Windows user, click here to get started. If you’re on a Mac, click here to get started. We also have a separate tutorial if you’re using Linux, which you can find here. All of the methods outlined in these guides use free software.

How to Compress PNG Files in Windows

  1. Start out by heading over to the PNGGauntlet home page. Click the Download button and install PNGGauntlet as you would any other Windows program. Once the installation has completed, place a check in the box labeled Launch PNGGauntlet and click the Finish button.

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  3. The first time you use this tool you may want to save the original files and have the new ones created in a different folder. Eventually once you’re happy with the program, you can set it to simply overwrite the existing files after they’ve been compressed. So click the button at the end of the Output Directory: field.

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  5. Select the folder (or make one) that you want to save your compressed PNG files in. Click OK when you’re done.
  6. As illustrated in the screenshot below, you’ll see the path to the directory where your images will be saved. Now, click the Add Images button.

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  8. Navigate to the PNG files you want to compress, and select them all. Click Open.

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  10. Now it’s time – click the Optimize! button.

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  12. PNGGauntlet will now start compressing your files. This process can actually take quite a while, depending on two main things – how many images you’re working with, and how fast your computers CPU (processor) is.

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  14. Once completed, you’ll see how much each file was ‘shrunk’ and how long it took to complete the entire procedure. As seen in the screenshot below, it took about 15 minutes to work on 15 PNG files, but the resulting files are considerably smaller now!

    Take a moment to view some of the ‘before and after’ images that you just compressed. You’ll see that there was no change to the ‘quality’ of the image, it’s simply smaller in size.


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  16. Once you’re happy with the tool, you can place a check in the box labeled Overwrite Original Files.

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  18. That’s it! One last suggestion – if you’re going to compress hundreds of images at once, you may want to let the program run over-night, while you’re not using your PC. If you are running PNGGauntlet while using other programs, try to minimize how many you’re using, and close the programs not in use. That will also help speed up the compression process.

How to Compress PNG Files in OS X

  1. To compress PNG files on your Mac, head over to ImageOptim home page and click the Download button. Once the download has completed, double-click the ImageOptim.tbz2 file to uncompress it.

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  3. Drag the file ImageOptim.app to your Applications folder, and launch it from there.

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  5. Select ImageOptim from the menu bar, and then Preferences from the list.

    On the General tab, place a check in the box labeled Backup original files before savingif you want to keep backups of the files before you compress them. I personally don’t bother, but you may want to try it out at first so that you can compare and confirm the image looks exactly the same after it has been compressed.


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  7. Simply drag-and-drop .PNG files into the main window of ImageOptim.

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  9. Right away it will start to do its thing. You’ll be able to watch the progress as the program shrinks your images.

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  11. Once completed, you’ll be presented with a summary of how much space was saved/files were shrunk. You’ll also be able to see exactly how much each individual file was shrunk by looking at the Savings column.

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  13. That’s all there is to it! As I mentioned in the Windows section, compressing PNG files can take quite a bit of time – depending on how many you’re compressing at one time, and how fast the speed of your CPU (processor) is. If you’re working with a lot of files, you may want to let ImageOptim run over-night. If you’re using your Mac while you compress PNG files, you may want to minimize the number of programs you have open, as that will help speed the process up too.
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