When to start opening the select list? On mousedown? Or on click? And Why?

  • Component: select aka. dropdown
  • Platform/system: web, non-touch device (laptop with trackpad or desktop with a mouse)

Is there a guideline, convention, or some studies done which can help developers/designers decide when to open the select list exactly? On mousedown or on click?

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Some custom third-party select implementations open the list first on click (mousedown+mouseup on the same element), whereas other implementations - especially the native ones - open it already on mousedown. Try, for example, the native HTML <select> element in your browser.

In my observation (using a Windows machine), all browsers opened the native select list consistently on mousedown, so there must be some guideline or convention when to open the <select> list with reasons behind it.

Personally, I'd also prefer opening the list on mousedown to improve perceived performance as well as consistency with the native behavior. But instead of personal opinion, I'd like to know what the general recommendation is (if there is any) and why with some numbers.

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