That's a great question, and one I've wondered myself when trying to dispose of a large pizza box on a city street. The honest answer is: it depends. Most standard urban trash cans you see on sidewalks are designed for everyday litter like coffee cups, wrappers, and small bags. Their openings are often not large enough to accommodate an unfolded, full-size pizza box.
You might be able to force a box through if you fold it diagonally or crush it down significantly, but it's not ideal. For bulky items like large pizza boxes, it's always best to look for a larger, open-top dumpster or a designated recycling bin if the cardboard is clean. If neither is available, taking the item home for proper disposal is the most responsible choice. This helps keep our sidewalks clean and prevents overflow around public bins.