What the platforms actually specify
- Windows guidance puts the confirming action first, with cancel to its right.
- Apple's guidance puts the button that performs the action furthest right, with cancel to its left — the exact opposite arrangement.
- Android's guidance places the dismissive action on the left.
- So there is no order that is correct everywhere, and an argument about which is better is an argument about which users you have.
Why testing may mislead you
One answer raised a genuine complication. Because one desktop convention has trained an enormous number of people for decades, a usability test will tend to report that users expect that order — but what it is measuring is the conditioning rather than any underlying preference. That does not make the finding wrong. It does mean a test result showing familiarity should not be read as evidence about what is inherently more natural.
The advice that survives the disagreement
- On the web, where there is no single platform to defer to, pick one arrangement and use it consistently across the product.
- Make the primary action visually prominent regardless of side. One answer argued this matters more than the order, since roughly half your users will find any given order unexpected.
- Label the buttons with what they do. A button reading Delete or Save is identifiable by reading it, which reduces how much the position has to carry.
- Keep it consistent everywhere in the interface, so people learn your arrangement once rather than checking every time.
Where the thread ended up
Nobody produced evidence that one side is intrinsically better, and the most-voted answer's first instruction was to test with your own users. The practical reading is that this is a convention question rather than a perception one — the cost of getting it wrong is not confusion so much as a moment's hesitation, and consistency is what removes that moment.