Are you saying London doesn't have crosswalks? I find that hard to believe.

London has plenty of pedestrian crossings, but they're unmarked, at least not in the same way - a stop line for cars before the lights, sure - except for 'zebra crossings', which look different, have different rules (no traffic lights and cars must give way to pedestrians) and would never be called a 'crosswalk'.

I suppose they just don't need to be, because not using one isn't 'jaywalking'. If there's too much traffic you identify a safe crossing by zebra stripes (or flashing beacon) or traffic lights or island.

When reCaptcha first asked me to identify the 'crosswalks', sure, I guessed it must be the road markings. But I just (still, to this day) select all the road markings that aren't obviously just centre direction seperating lines. I might get loads wrong, no idea.

They are called zebra crossings outside the US. They also look different.

My understanding is that 'crosswalks' are all legal points (because 'jaywalking' at another point is illegal in the US) of pedestrian crossing.

At least in the UK, zebra crossings are a tiny subset of pedestrian crossings. (And you can cross the road wherever you please.)