FindFit, Mathematica selects an optimal algorithm when
Automatic is selected.
I'd like to know the name of the method applied to the
FindFit computation. Is there any option to explain that?
As noted by @Ｊ.Ｍ., the docs say that the default for
FindFit is SVD for linear least squares and Levenberg-Marquardt for nonlinear least squares. If it is important for the end-user to know explicitly the method used, then the user should explicitly define the method.