What focal length is best for a first prime lens?

Across the reviewers we read, a 35mm or 50mm prime is the most-recommended starting point. A 50mm (or a 35mm on crop sensors) gives a natural perspective and a fast aperture for portraits and low light, which is why budget options like the Canon EF 50mm f/1.8 STM and Nikon 35mm f/1.8G DX show up so often in beginner recommendations.