Image Resolution in Preview does not save after altering

I can confirm that Sequoia saves the resolution setting, whereas Tahoe reverts to 72 ppi when reopening an image (though it is not resampled).

Bugs can be reported to Apple here:

Feedback - macOS - Apple

Yes, resample image does something – it resamples the image, aka scaling. If you uncheck the box, then adjust the size or resolution the other changes, e.g. an image that's 1000 pixels wide at 100 ppi becomes 500 pixels wide at 200 ppi; if you check the box to resample then go from 100 to 200 ppi, the computer interpolates and creates new pixels – that's resampling.

Personally, I use Photoshop even for simple manipulations like that, or if I really need increase the resolution (upsample a lot) then I use Topaz AI. Both are paid, but Adobe does offer a free online image resizing tool that may tide you over until Apple fixes Preview:

https://www.adobe.com/express/feature/image/resize

There are a bunch of other apps that can resize images, check the App Store.

ashprint wrote:

I'm sorry, it's actually Tahoe 26.1. I tried using other apps and even Adobe, but the image size increases significantly :(

For example, if the base image is 2.5 MB, other apps change it to 5.5 MB or even 7 MB, whereas the Preview app keeps it around 2.7 MB at most.

If the file size is increasing, then you're doing something other than simply changing the resolution. You are either increasing the pixel count of the image (keeping the dimensions the same but increasing the resolution will do that) or you are saving the image at a higher quality setting (which is useless).

A 1200x1200 pixel image can be 16.67" x 16.67" at 72 dpi or 4" x 4" at 300 dpi, the file size will be identical. But if you take the 16.67" x 16.67" at 72 dpi and make it 300 dpi without changing the dimensions, then you will have a 5000x5000 pixel image and of course that's going to be a bigger file.

Well, using a different graohics app is one. Or, you could wait and see if Apple changes Preview in some future update of Tahoe.

I also run an online shop, and I rely on Preview to edit my product images. After updating my Mac to Tahoe 26.0.1, I can no longer change the resolution from 72 dpi to 300 dpi. Even images I previously uploaded at 300 dpi are being altered as soon as I open them in the new Preview app.

I sell JPG images and adjusting the DPI in Preview is a crucial part of my workflow, so this issue has completely disrupted my work.

mystic97 did you ever find a solution to this problem?

I’ve tried everything on my end and nothing seems to work. My last option is downgrading back to Sequoia (ugh!).

I'm sorry, it's actually Tahoe 26.1. I tried using other apps and even Adobe, but the image size increases significantly :(

For example, if the base image is 2.5 MB, other apps change it to 5.5 MB or even 7 MB, whereas the Preview app keeps it around 2.7 MB at most.

I upload these to Etsy, and they have strict size restrictions, so keeping the file small is really important.

Are you saving the image after you resize it and change the dpi? Seems to work for me.

mystic97 wrote:

I have tried saving it after resizing. It doesn’t work. I’ve tried it with PNG and it works fine, but with JPEG, it does not.

I missed where you specified JPEGs.

ashprint wrote:

I also run an online shop, and I rely on Preview to edit my product images. After updating my Mac to Tahoe 26.0.1

The current version of macOS is 26.1. No idea if the issue has been addressed or not, but that's a place to start.

To repeat: Adobe does offer a free online image resizing tool that may tide you over until Apple fixes Preview:

https://www.adobe.com/express/feature/image/resize

There are a bunch of other apps that can resize images, check the App Store.

FWIW, jpgs are limited to 72 dpi in Preview. You will have to use a different graphics program to set a jog to 300 dpi.