I thought i'd be able to do this with the built-in Preview app, but I can't find a way to do that.

I have an image i'd like to reduce the opacity to 50%.

Can anyone advise if there's a way to do this with built-in applications that come with MacOS or if this needs GIMP or another image editing tool? I'd rather not install GIMP (if I can avoid it) just for this.

  • What is the end use of the image - for instance if it's going on a webpage you can use CSS to adjust the opacity?
    – Mr R
    Mar 13, 2021 at 7:20
  • @MrR Yes, it's going on a webpage however I have limited control as it is set using a Wordpress plugin. I'd like to set the opacity on the background image but not the entire container.
    – crmpicco
    Mar 13, 2021 at 7:33
  • Perhaps wordpress wiki on featured image transparency can help? (sorry this seems like it might help but wordpress is not my jam).
    – Mr R
    Mar 13, 2021 at 7:43
  • See this answer to a very similar question: apple.stackexchange.com/a/251184/22003
    – dan
    Apr 12, 2021 at 17:15

2 Answers 2


Yes, you're going to need a graphic image editor, be it GIMP, or Pixelmator, or Affinity Photo, or Adobe Photoshop, or other.

Having some sort of program of this type is bound to come in useful again. Preview has its uses, but it's not a general-purpose image editor.


You don't strictly have to install something, there are always online tools like https://www.online-image-editor.com/.

I would definitely say that you have many options (there is even a backwards way with word like described here https://www.maketecheasier.com/make-transparent-images-osx/ -- WHY??? oh well...

it's a user's world now, enjoy.


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