The sidewalk is for pedestrians, not cyclists.
What are the exceptions?
- If there are no or very few pedestrians on the sidewalk, I'll ride there for a few yards to start or end my trip - like from a convenient curb cut to/from the door of the store I'm going to.
- Sometimes there will be a high traffic, high speed street with no bike lane that is rather hairy to ride on, but has a sidewalk that is hardly used by pedestrians - not uncommon, since those sort of streets aren't usually in "walking neighborhoods". Then I'll ride on that sidewalk if I feel unsafe on the road.
But otherwise, stay off the sidewalk. Pedestrians move unpredictably, they stop and turn and back up and dart right and left, it is dangerous to ride around them. Children and dogs are the worst. You can get plenty hurt bouncing off a pedestrian and falling into a parked car or a plate glass window, and worse yet you can hurt someone else. For a little kid or an elderly person, being rammed by a bike and rider is not a minor thing.
To this I would add that sometimes you might have to ride on a sidewalk for a bit when transitioning between the road and an MUP, or between MUPs over a bridge, or something like that. Here, I can think of at least one spot where cyclists are actually directed to use the sidewalk, then cross traffic in the crosswalk to get from a cycle track to an MUP.