For some reason, when I change the DPI to 300 in Photopea/Photoshop, the images become pixelated. They are correct size, however, to upload to Zazzle. If I upload them to the products, does Zazzle automatically fix that so it still looks good?
When you increase the DPI in Photoshop, it changes the size of the artwork. Make sure to check the size of the art. It may now be too large or too small. I typically use 300 DPI and 2480 pixels for height and width, which results in a nice, crisp result.
The lowest resolution you should use is 150 dpi. But that still can result in low image quality. You will need to fix the resolution on any product where you get a yellow or red warning sign in the design tool. You will need to fix the resolution yourself either in Photoshop, a paint program, or image upscale app (there are some free ones available).
It doesn't change the size of the artwork in pixels, just inches. So if you have a 2400 pixel square image, with 72 DPI, and you change it to 300 DPI, leaving "resize artwork" unchecked, it will still be a 2400px image.
