Can't reduce .jpg file size with Preview in Big Sur

All of that can in principle be done in Preview, which we all have. Unless the image file that is to be converted is already in the user Photos library, using Preview is much faster.

The problem, as the OP described and can be easily confirmed, is that in the present version (and several recent versions) there is this bug. Changing the dimensions works fine, I do that all the time. It’s just that quality slider that is not being honored.

jeffporter228 wrote:

Since upgrading to Big Sur I can no longer reduce the file size of a .jpg image with Preview. There was a previous thread about this, but the solutions offered don't work on my computer. To my knowledge there are three options to accomplish file size reduction in Preview: 1 - adjusting the file size via the Markup button, 2 - adjusting the resolution under the "Adjust Size" option under "Tools", and 3 - resaving the file and adjusting the file size under the "quality" slider. On my computer none of these options will change the file size, it simply reverts back to the original size when saved. This should be a simple task to do and it's really frustrating that it's not working in Big Sur. Any fixes coming from Apple? This problem exists on both my MacBook Pro and iMac, both running up-to-date versions of Big Sur.

In Preview>File >(Hold the Option key ) Save As

jeffporter228 wrote:

Hi, thanks for the reply. Preview>File>(Hold the Option key) Save as - this brings up the "Quality" slider, which I mentioned in my original post. While this slider shows the file size being adjusted, when the file is saved it reverts back to the original file size, hence it doesn't actually reduce the size. This is definitely a bug...

 you can submit your bug report using the following link: Apple Feedback http://www.apple.com/feedback 

Did a test (MacMini M1 - Big Sur 11.6). Same problem here and is not a filesystem problem as happens sometimes as when I open it the quality is the same as the original although saved at the extreme minimun quality (and shoud therefore be bad to see). Therefore the file IS NOT reduced in quality/size as you correctly state. At least for me and you.

Regarding your question "Any fixes coming from Apple?" nobody knows what Apple is going to do in the future and Apple is not present in this forum directly but surely will be fixed in future releases. Meanwhile you can report the issue here: www.apple.com/feedback

As a workaround, until this gets fixed: Save the file as png, and THEN if you open the png file and Save As in jpeg, the slider works. AFAICT it is only when the file is already in jpeg format that the slider is ignored.

Are you wanting to reduce the file size, i.e. MBs or the image size, pixels?

A better solution would be to export the file out of a Photos library and use the JPEG Quality option:

Or use a 3rd party app to resize either the image size of file size like Resizeit or Resize Master:

There are a number of easier to use options than using Preview.

+1