Splitter or riving knife–what's the difference?

I'm preparing to purchase a tablesaw and have been researching the features of different models. What's the difference between a riving knife and a splitter?
—Jamie Handel, Chesterfield, Va.

The goals of a riving knife, shown above, and a splitter, below, are the same, Jamie. Both sit behind the blade to prevent the two sides of a cut piece of wood from pinching or rotating into the blade. This, in turn, prevents the workpiece from kicking back at the operator.

However, a splitter typically doesn't change height, while a riving knife raises and lowers with the blade. Also, the top of a true riving knife stands just lower than the top of the blade, so it doesn't have to be removed for most non-through cuts such as dadoes, grooves, and rabbets.

Every tablesaw comes with a splitter (it holds up the blade guard), and you can add an aftermarket splitter, such as the one shown bottom, without a guard. Soon, riving knives will be just as common because Underwriters Laboratories (UL) made them a UL-listing requirement for new tablesaw models introduced since January 2008. Existing tablesaw models are grandfathered in until 2014, when they, too, will need riving knives for UL listing.