Double click

A double click is not two clicks. It is one gesture the system recognises when two presses land close enough together in time and in space, and the threshold is a setting the reader owns: every desktop operating system exposes a double-click speed, and some people have it turned right down. That is why a double click can never be the only way to reach a command. Anyone who cannot produce two presses inside the interval, or who is using a touch screen where the gesture barely exists, is simply locked out of it.

It survives where it means something a single click does not. In a file manager, one click selects and two open, which is the distinction that gave the gesture its career. In a spreadsheet or a table of editable cells, two clicks enter edit mode on the value you already selected. In text, two clicks select a word and three select the paragraph, which is browser behaviour you get for free and should not break. What these have in common is that the single click already does something useful, so nobody is stranded by not knowing about the second one.

On the web the event is dblclick, and it arrives after two full click events, not instead of them. Your click handler runs first, so the two behaviours have to compose: select, then open. If they conflict, you are fighting the platform, and the usual fix is to move the destructive or navigating action to a button rather than to try to swallow the first click with a timer. Suppressing that first click for a few hundred milliseconds to see whether a second is coming makes every single click feel broken.

Watch what a double click does to a form. Two presses on a submit button send two requests unless the button disables itself on the first, which is one of the oldest bugs on the web and is still worth checking.