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forza69

macrumors 6502a
Original poster
Jan 30, 2010
780
126
I recently upgraded to a 15 inch rMBP and it is the first Mac I have ever owned. I need to take some screenshots and upload them to a site but whenever I try and upload it says file too big (8-10MB). Is there an easy way to lower the file size to say, 2MB? I'm using the 1920x1200 resolution setting at the moment. TYIA
 
Nov 28, 2010
22,670
31
located
As screenshots are stored in PNG format, file sizes are big, especially with your resolution.

However, you can open those PNGs via double click in Preview, then adjust the physical size via Menu Bar > Tools > Adjust Size and enter pixel values you find enough.
Then you can save the PNG as JPEG via File > Save As (CMD+SHIFT+S) > select Format > JPEG and be done with it. That should get you files smaller than 2 MB, if the resolution is not 3840 x 2400 pixel or so.
 

Bear

macrumors G3
Jul 23, 2002
8,088
5
Sol III - Terra
I believe the default for screenshots is PNG, you could switch it to JPG which will produce noticeably smaller files. In Terminal:
Code:
defaults write com.apple.screencapture type jpg
killall SystemUIServer

This would save having to go through Preview.
 

switon

macrumors 6502a
Sep 10, 2012
636
1
RE: jpg instead of png...

I recently upgraded to a 15 inch rMBP and it is the first Mac I have ever owned. I need to take some screenshots and upload them to a site but whenever I try and upload it says file too big (8-10MB). Is there an easy way to lower the file size to say, 2MB? I'm using the 1920x1200 resolution setting at the moment. TYIA

Why not change the default format for screen shots:

Code:
defaults write com.apple.screencapture type jpg; killall SystemUIServer

Regards,
Switon

P.S. Whoops, but Bear beat me to it.
 
Last edited:

forza69

macrumors 6502a
Original poster
Jan 30, 2010
780
126
Thanks guys! I tried out an app called RetinaCapture and it seems to do the job easily. I'll probably uninstall it now and do what you guys recommend which is even easier.
 

alinpanaitiu

macrumors member
May 29, 2021
42
45
Romania
For people still looking for a solution, I wrote a small app to optimise the screenshot file size automatically.

It is called Clop and you can find it here: https://lowtechguys.com/clop



It’s been 10 years since the last post, but people are still bumping into this. Solutions like ImageOptim exists but they are manual and take time.

This is the first Google result for the issue so I’m hoping the necroposting can be excused.

Clop also converts the screenshot to both jpeg and png and chooses the smallest one. JPEG is good for images with lots of detail like photos, while PNG is good for images with big smooth areas.

The app is open source at https://github.com/FuzzyIdeas/Clop
 
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