Who is behind it
PhysRef has no company behind it, only a single independent developer, who also runs CalcRef, ChemTable, Trigonify and OpticBench, which cover calculus, the elements, trigonometry and optics. They are named here so the connection between them is out in the open; this page does not link to them.
Where the formulas and constants come from
Each formula is a single record in the site's data files, and the formula pages and printable sheets render from those records rather than from separate copies. The constants table follows CODATA values and the 2019 SI redefinition, with the defining constants such as c and h written at their exact values.
Where the same law appears under two categories, the shorter entry is marked as a duplicate and its page points search engines at the fuller one.
How guides are credited and dated
You will not find a person's name at the top of the guides; they are signed PhysRef. Search engines read the same thing from the page markup, where author and publisher are both the PhysReforganization. The date printed on a guide marks when its text last changed.
How the practice questions are made
The practice set is generated from those same formula records. A question asks which equation a named formula is, what a symbol stands for, or the SI unit of a quantity, and a wrong option is only ever drawn from entries that never pair with the right answer anywhere in the data. The free daily round of 10 questions is the same for every visitor on a given day.
What it will not do for you
PhysRef is a study aid. Your course, your instructor and your textbook still come first, and it is no authority for design or engineering work, where the governing standard and a qualified engineer decide. Every formula rests on assumptions, such as no friction or a point mass, and a page cannot know whether your problem meets them.
Reporting an error
Spot a wrong formula, a unit that does not match, or a guide that misstates something? Write to [email protected] with the page address. The privacy notes and the terms cover everything else.