This issue is being filed because @giacomo-petri correctly pointed out that while specs ( html aam nor accName ) clarify the order of precedence for instances where a placeholder attribute and an aria-placeholder attribute are specified on the same element.

From my testing today, it fortunately looks like almost all browser implementations are in sync, where placeholder takes priority over aria-placeholder. The only outlier i found was when testing with Firefox on macOS, where that one instance combined the native placeholder value and the aria-placeholder value into a single string exposed to users.

I have created a PR to clarify these steps in HTML AAM