YMMV

YMMV is a jargon abbreviation used in the Ars Magica Fan Community. It stands for "Your Mileage May Vary."

The meaning is, loosely, "I like this idea, but you may prefer some alternative; this may not work for you." The implication is that the writer admits that legitimate differences of taste or opinion exist, and that such alternatives are equally valid as the idea being suggested.

To speculate on where the term came from, I seem to remember television advertisements for cars in the 1980's (when most of the COOFs from the Berk List were growing up) saying what the cars' government ratings of fuel economy were (the term is "gas mileage"). Such statements were always accompanied by a footnote to the effect that "your actual mileage may vary." The car company was advertising the the gas mileage the car got in laboratory tests, while at the same time disclaiming that those figures were actually achievable under normal operating conditions. Hence, the car might not work quite as well as the numbers suggest it should.