Why does White move first in chess?

The rule today

FIDE's Laws of Chess say it in the very first article: the player with the light-colored pieces, White, makes the first move, and then the players move alternately. In tournaments, the pairings decide who gets White. At home, you decide. The rest of the rules are in the chess rules.

Once you could choose

For a long time it wasn't settled. The laws of chess that George Walker published in London in 1846 say that whoever has won the first move also chooses the color. Wilhelm Steinitz wrote in 1889 that players drew lots for the move and the choice of color, but that in international and public matches and tournaments it was the rule for the first player to have the white pieces.

Exactly when the rule was first written down isn't known. One of the oldest examples chess historians have found is in the book of a New York tournament from 1880: the player who has the move is always to play with the white pieces. In published games, White was already moving first by about 1862, according to the same source.

Is moving first an advantage?

Yes, but a small one. Here's how 2.6 billion online games between club players ended, 660 million of them between strong players, in blitz, rapid, and classical.

That's why colors are shared out carefully in tournaments. In the Swiss system, nobody gets the same color three times in a row, with a few exceptions. More under How does a chess tournament work?