Does searing meat seal in the juices?

The idea that searing forms a crust that locks juices inside is one of cooking's most durable myths, and it is wrong. It traces to a 19th-century chemist, Justus von Liebig, whose theory was disproven long ago, side-by-side tests show seared meat does not retain more moisture, and can actually lose slightly more, because the high heat that browns the surface also drives off some water. A seared steak is not a sealed vessel; juices pass right through that crust.

But searing is absolutely worth doing, just for a different reason: flavor. The browning is the Maillard reaction, a cascade of chemical reactions between amino acids and sugars at high heat that creates hundreds of new flavor and aroma compounds and the deep savory taste and color of a good crust. That is the real payoff, and it is enormous. So sear your meat, but sear it for the crust and taste, not to trap juices. The actual keys to a juicy result are not overcooking (use a thermometer and pull it at the right internal temperature) and resting the meat after cooking, which lets the juices redistribute rather than spilling out the moment you cut in.