Upon activating the toy, an egg appears on the screen. After setting the Tamagotchi unit's clock, the egg will wiggle for several minutes, and then hatch into a small pet. In later versions, inputting the player's name and birthday is also required when setting the clock, and at birth, the player can name the pet and learn of its family group and/or gender. The player can care for the pet as much or as little as they choose, and the outcome depends on the player's actions. The first Tamagotchis could only be paused by going to set the clock, effectively stopping the passage of time in the game, but in later models a pause function was included.
Pets have a Hunger meter, Happy meter, Bracelet meter and Discipline meter to determine how healthy and well behaved the pet is. There is also an age and weight check function for the current age and weight of the pet. Filling up the Hunger meter can be achieved by feeding the pet a meal (usually a loaf of bread) or a snack (usually a piece of candy). Filling up the Happy meter can be achieved by playing mini games with the pet or by feeding it a snack (there are no limits to this, but there are limits to how many meals can be fed).
If the pet gets sick, a skull icon appears next to the pet as it sits still at the bottom of the screen, with an unhappy expression. The pet can become sick for a number of reasons such as overfeeding of snacks or failing to clean up droppings. The pet can die if sickness is left unchecked. The pet can be cured by pressing the "Medicine" option. Usually a pet will not play or be fed a meal when sick.
Pets would often fall asleep during the night time. Originally players had the option of manually turning off the light when the pet fell asleep (it would turn on the light by itself when it awoke). In order to raise a healthy pet, players were encouraged but not required to turn off the lights when the pet fell asleep. In recent versions, the pet turns off the light on its own when it went to sleep. Recent versions also allow waking the pet for a short time once it has fallen asleep. V5 had the three children look outside on the window when they wake up in the morning and before bed at night.