My daughter started using a balance bike around 18 months. By the time she was 2.5, she zoomed around on it and had started asking about pedals. We got her a pedal bike two months before she turned 3, with the expectation that we might have to take the pedals off for a few more months. Instead, within a few days (maybe 2 total hours of practice?) she was riding confidently and totally by herself--at not quite 3 years old.
It's so different than the challenging, scary attempts to remove training wheels when my siblings and I were 5 or 6 years old. One of those things where I didn't realize the science and tradition on teaching kids to ride bikes could change so dramatically within two decades!