Web browsers will scale images to 200% when they detect a high resolution display, so a 2280 px image will also be scaled to 200% (or scaled to fit the window if there aren't enough screen pixels available). If the display is standard resolution, no scaling will occur.
Some websites use special coding to prevent the scaling, it requires two versions of each image - one at 1x and 2x.
The 1x version will be served to standard resolution displays, and the 2x version will be served unscaled to high resolution displays. This is done with a script that tricks the browser to think that the image already has been scaled. At least that's how it worked when I implemented this on my website some years ago.
If the websites you display your work on don't have this feature, the best you can do is to make the image look as good as possible at it's native size (1140 px). You can assign a keyboard shortcut to View > 200% to check how the image looks when scaled.
Do I just set it to 144 dpi and make it 1140px? That way, its not so blurry at 2x? Also, making it 2280px is not comfortable even at 72dpi
By @SB-W
PPI (it's not DPI) stands for Pixels Per Inch, and is optional metadata used to calculate printed dimensions.
Pixel dimensions divided by PPI = Printed dimensions in inches.
For screen viewing, PPI is irrelevant, and not even required. The image will display according to its pixel dimensions no matter what the PPI value is.
If you export from Photoshop, the PPI value will be stripped out because it's not needed for screen viewing.
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