Photoshop 2024 saving flattened images as PSD

[lizwadephoto]

Photoshop 2024 on a Macbook. I open a JPG image, make some changes, flatten if needed (not always needed because I'm not always creating additional layers), and when I hit CTL+S, Photoshop wants to save as a PSD. I have to click on 'Save as a Copy', then erase the "copy.jpg" at the end of the filename, and then click 'Save'. This happens about 50% of the time and I cannot figure out why. Help!

[D Fosse]

As I'm sure you know, jpeg doesn't support 16 bit/layers/transparency/alpha channels.

Are you cropping? If so, check the crop tool options. If it's set to hide cropped pixels, instead of delete, the result is a floating layer, which jpeg does not support. This happens even if you just flattened. This is just because pixels outside the canvas requires a floating layer.

[lizwadephoto]

Interesting! I know it has happened at times when I haven't cropped, so I don't think that's the problem...

[D Fosse]

Well, it has to be one of these four: 16 bit, floating layers, transparency or alpha channels. These are the things not allowed in a jpeg.

I've tested this on several occasions, because often people claim otherwise: If you resave a jpeg without violating the jpeg specification, then Photoshop will resave as jpeg by default.

Another thing is that you really shouldn't resave jpegs at all. It will deteriorate with every resave.