I'm not saying you CANNOT use a checkbox outside of a form. I'm saying they gradually became different UX widgets that serve different purposes. You can use pr

I'm not saying you CANNOT use a checkbox outside of a form. I'm saying they gradually became different UX widgets that serve different purposes. You can use pretty much any widget to store a boolean state. A select? It works. Radio buttons? Works. Checkbox? Of course. Typing "1" or "0" in a text input limited to integers between 0 and 1 inclusive? Why not. But semantics matter, and so does the principle of least surprise. Nowadays users expect an immediate result when toggling a toggle button. Not as much when they toggle a checkbox.