Hatcheries are the lynchpin by which the entire zerg infrastructure is built. Not only do they produce workers and serve as a place to drop off resources, they also produce units. Each hatchery spawns larvae, which you can morph into workers, overlords, or army units. On its own, a hatchery will spawn up to a maximum of three larvae over time. While other races can build additional production facilities without expanding, the zerg player has to build an entirely new hatchery to be able to spend excess money. Therefore, when you don’t feel safe expanding, you may need to build an additional hatchery inside a base that already has one. Though it’s a significant investment, this “macro hatchery” will provide you with the additional larvae you need. Having ‘extra’ hatcheries will give you something to do with any surplus resources, and they’ll also allow you to produce and replace units quickly between and during battles. In the event that your main base is overrun, additional hatcheries at your expansions will give you the extra larvae you'll need to quickly rebuild.

Most zerg players build their second hatchery at the expansion closest to them at the start of the game. One hatchery is generally not enough to support both a growing economy and unit production, even in the early game. Because expanding is generally a zerg player’s first objective, stopping the creation of an early expansion can be very crippling. Should you find your natural expansion blocked, often the safest way to proceed is to take the next-closest expansion rather than delaying the construction of your hatchery.

Once you have multiple hatcheries constructed, use hotkeys to speed up your production. You can assign all of your hatcheries to a control group by selecting all of them with the shift key, holding down the Ctrl key, and then pressing the number you wish to assign it to (i.e. Ctrl + 1). Once your hatcheries are assigned to a group, pressing that number will select them all at once, allowing you to evolve all of your larvae without having to individually select each hatchery.

Queens have an ability called “Spawn Larva” that dramatically speeds up unit production. When used, it causes the hatchery to produce an additional four larva after a period of time. Learn more about queens.

This zerg player has three hatcheries in their main base.

Hordes of zerg come from multiple bases.

A zerg player builds at their expansion.

If you can catch an expansion early enough, you can stop it.