Wolfram: File Name Extension

.nb

Wolfram Notebook file name extension.

.wls

WolframScript file name extension.

.wl

General purpose Wolfram language file name extension, also for Wolfram packages. (introduced about 2015.)

• Difference Between Wolfram Language, Mathematica, WolframEngine, WolframScript

.m

Old convention of file name extension for Wolfram language package files. Still supported. (the m standard for Mathematica.)