major differences in the yfz450r over there years? 2013 on up

Hi everyone, I'm coming back to the sport after 15ish years. I'm in the market for a used yfz450r and was trying to find out if there have been any major changes to them over the years or if they've remained relatively the same? I'm looking at some between 2013 and 2021, so I'm trying to weigh out my options. Any help is greatly appreciated!