Short question: why if I do screenshot on a Mac and crop it, and see it using Preview, it is a good size but when posted to Internet, such as StackOverflow, its width and height always double? I can resize 50% width and height but the image is not as clear (not retina). So how can I use that image and not have it show up twice the width and height?)

I sometimes take a screenshot on a Mac (OS X Mavericks), by CMD-Shift 4, and resize it to 50% width and height in Preview.

But when posted on the Internet (for example, on an online forum or on ibb.co or imgur.com) , it is double size again. I tried 50% and then resolution changed from 144 to 72 for the original image, and the same: it is still double size. I had to do a 25% and also 72, in order that it is the proper size.

It is really weird. Why 25% and not 50%, and how does the 144 or 72 matter? (or does it?)



I'm not quite sure what you mean. I tested it with a screenshot (see above) and reduced the resolution to half, uploaded it here, it's still the new resolution that I chose in Preview.

Maybe you can try the following:

  • Change the resolution in Preview
  • Close the image
  • Right click on it, check Get Info, then "More Info", there you should find the current resolution which should be slower than before
  • If this does not work for you, maybe try a tool like ImageMagick that offers a lot of options for manipulating images.


  • Hi Harpe, remember to provide a solution in an answer :)
    – pallox
    Aug 29 '18 at 13:04
  • You're right, I added some steps to test or try something different.
    – Harpe
    Aug 29 '18 at 13:59

Why not change it by size (inches or pixels) instead of percent. Then you could be sure of the size.

Not the answer you're looking for? Browse other questions tagged .