No matter what year it is, information about what DPI to set for photos published on the internet is still being repeated. “Just use 72” is probably the most common opinion. Of course, 72 is enough. Just like any other value, even 1. If it’s 10,000, it won’t change anything – the photo will be identical.
This is not secret knowledge, and I know that most people probably know what DPI is. Unfortunately, sometimes someone comes up with their own theory and would bet their hand on it.
Impact on Internet Photos
In reality, we often talk about DPI (dots per inch) when we actually mean PPI (pixels per inch). However, the PPI of photo chosen in, for example, Photoshop corresponds to the later DPI when printing (of course, if it is not changed along the way). And all the advice regarding “internet DPI” refers to PPI and what is set as “resolution” in the resize window (not to be confused with dimensions), which is why I use these terms interchangeably here. PPI can be changed at any time, both from 300 to 20 and to 2000. It has no effect on the digital file because it is just information for the printer.
Of course, displays have their own PPI, which determines how many pixels per inch and depends on how sharp the photos and everything else will be. However, the display’s PPI has nothing to do with what is set in the image file. Only the dimensions given in pixels (height and width) matter for its quality.
Examples
Below, I am placing the same photo with DPI 1 (one) and 25000 (twenty-five thousand):
1
25000
Below is an additional example. The photo is not processed in any way, nor sharpened after resizing, and the individual files differ only in DPI:
10
72
300
999
There is no difference, but if you see it, there is certainly a doctor who can help you.
Prints
The difference will be in print, which is obvious. Below is a file resized for the internet, printed with DPI 300 and 72:
But as already mentioned – it can be changed at any time, for example from 72 to 300 or higher.
Meanwhile, when printing web pages, text documents, etc., photos can have any PPI value set because the photo is scaled so that its size relative to the text is the same as on the monitor. That’s why there is no difference between 1 and 25000:
Print of a web page with a DPI 1 photo
Print of a web page with a DPI 25,000 photo
Summary
I have nothing more to add. The answer to the question asked in the topic was already placed in the introduction to this post, which probably reduced its viewership by 3/4… DPI on the Internet does not matter. That’s all.