Optimizing images on the Mac

Optimizing images on the Mac

The performance of a website or blog is largely determined by the size of the images that have to be downloaded. ImageOptim is a free and open-source application to optimize images without losing quality. Smaller images not only decrease the loading time it also has a smaller impact on the storage availability on your hosting platform. In this post I will take the image I take some screenshots I made with command shift 5 and show how to compress the images and the results.

Installing ImageOptim

Do not try to download ImageOptim from the AppStore. Those results are not the program you want. If you are a Homebrew user you can Install ImageOptim with the following command.

brew install --cask imageoptim


  • Open your browser and go to the ImageOptim website.
  • Click on the Download for Free button and then on save.
  • DoubleClick on ImageOptim.tbz2 will extract the ImageOptim.app file.
  • Drag the ImageOptim.app file to the Applications folder The application is now installed

Using ImageOptim and results

The first time you use ImageOptim you get a warning telling you dat this application is downloaded from the internet (like you did not know). Let Gatekeeper know you really want to open this application. Drag the images you want to compress to ImageOptim. The result depends on how optimized the source image was. If you use it on an image that was already highly optimized, you won't gain much. But in other cases, you win a lot. For the three png files, I used in this example the savings were more than 30%. That is a lot. Note that if you are writing a technical blog screenshots are the most used images.



If you are running a website or a blog it is important to optimize the images on your blog. ImageOptim is easy to install, easy to use, and very effective.