https://www.w3.org/TR/css3-selectors/#the-user-action-pseudo-classes-hover-act
The :active pseudo-class applies while an element is being activated by the user. For example, between the times the user presses the mouse button and releases it. On systems with more than one mouse button, :active applies only to the primary or primary activation button (typically the "left" mouse button), and any aliases thereof.
What is reality in Chromium, EGDE and IE? Only Firefox meet this requirement. I tested with <input type="button" />. I don't tested all elements. Please check middle button and right button.
Firefox: "left" mouse button
Chrome: "left", "right" and "middle" mouse buttons
Edge: "left", "right", "middle", "4" and "5" mouse buttons
Please note: in past only left button worked as :active. I think there shall be reported a bug due to current specification. Gecko based browsers (SeaMonkey, Firefox) works properly.
This misinterpretation in IE11, EDGE and Chrome spoils my solutions and I must add additional script for them to work properly...
Thanks for "4" and "5" button information about EDGE. I upgrade my script, I cannot test because my mouse has only 3 buttons.
I think also in "caniuse" the information about wrongly implementation of :active shall be added. I don't know how to report it to caniuse..
Most helpful comment
Firefox: "left" mouse button
Chrome: "left", "right" and "middle" mouse buttons
Edge: "left", "right", "middle", "4" and "5" mouse buttons