Do you need to rinse dishes before putting them in the dishwasher?

Scrape the big stuff into the trash, then load. Pre-rinsing wastes a lot of water and actively works against you, because modern dishwasher detergents are enzyme-based and those enzymes are designed to bind to food soils. Give them a spotless plate and they have nothing to work on, which can leave a residue film. On top of that, many dishwashers made in the last decade use a turbidity sensor that measures how dirty the water is and adjusts cycle length and intensity accordingly, so a pre-rinsed load can trigger a shorter, gentler wash that cleans the actual baked-on spots less well.

The caveats are narrow. Scrape or shake off bones, large chunks, and anything that will clog the filter, and rinse things that will sit for a day or more before you run the machine, since dried-on egg, cheese, and tomato are genuinely hard. Pull the dishwasher filter every month or two and rinse it, most people never learn it exists, and a clogged filter is the leading cause of a machine that suddenly stops cleaning well. Use fresh detergent, since the enzymes degrade with age and humidity, run a hot water tap at the sink briefly before starting so the machine begins with hot water, and skip the heated dry to save energy.