Boiled eggs are eggs (typically chicken's eggs) cooked by immersion in boiling water with their shells unbroken. Eggs cooked in water without their shells are known as poached eggs. Hard-boiled eggs are either boiled long enough for both the egg yolk and the egg white to solidify, or they left to cool down, which of itself solidifies them, while a soft-boiled egg's yolk, and sometimes even the white, remains at least partially liquid. The egg timer was so-named due to its common usage in timing the boiling of eggs.

Soft-boiled eggs
Soft-boiled eggs are typically cooked by placing the eggs in a pan of boiling water and then simmering.[1] British cook Delia Smith suggests placing an egg in cold water, bringing to the boil, and simmering: 3 minutes for a very soft egg, 4 minutes to make sure the white is set, and 5 minutes for an almost-set yolk.

Soft-boiled eggs are not recommended for people who may be susceptible to salmonella, such as very young children, the elderly, and those with weakened immune systems.

Serving
Soft boiled eggs are commonly served in egg cups, where the top of the egg is cut off with a knife or egg scissors, using a teaspoon to scoop the egg out. Other methods include breaking the eggshell by tapping gently around the top of the shell with a spoon.[4] Soft-boiled eggs can be eaten with buttered toast cut into strips, which are then dipped into the runny yolk. In the United Kingdom, these strips of toast are known as Soldiers.[5]

Hard-boiled eggs
Hard-boiled eggs are boiled for longer than soft-boiled eggs, long enough for the yolk to solidify.[6] They can be eaten warm or cold. Cold hard-boiled eggs can be chopped up to form the basis for egg salad. Hard-boiled eggs can also be eaten warm in an egg cup.

There are several theories as to the proper technique of hard-boiling an egg. One method is to bring water to a boil and cook for eight minutes. Another method is to bring the water to a boil, but then remove the pan from the heat and allow eggs to cook in the gradually cooling water.[7] Others prescribe cooking in continually boiling water over heat for a shorter period of time.[6]

Over-cooking eggs will typically result in a thin green sulfur coating on the yolk. Immersing the egg in cold water after boiling is a common method of halting the cooking process to prevent this effect.[7] It also causes a slight shrinking of the contents of the egg, easing the removal of the shell.

Hard-boiled eggs in their shells can be stored in the refrigerator for days to weeks.

白煮蛋指的是未剥壳的蛋（一般指鸡蛋）浸没在沸水中而煮熟的蛋。而水煮的去壳的蛋称为水煮蛋.煮得老的鸡蛋既非煮得足以使蛋黄和蛋清都凝结成形，亦非使之冷却后自凝;而半熟的鸡蛋的部分蛋黄甚至是蛋白是液体状的。煮蛋计时器也是因去用途而得名。

半熟的鸡蛋

半熟的鸡蛋一般是指放在一平底锅内沸水慢慢煨而煮出来的蛋。英国厨师迪莉娅史密斯建议把鸡蛋放在冷水中煮，到水开时用文火煨，三分钟后就有一个半数的蛋了，4分钟能使蛋清成形，5分钟蛋清蛋黄就几乎全成形了。

但是半数的蛋并不适合那些可能对沙门氏菌过敏者，像小孩子，老人以及免疫力低下着。

吃法

半熟的蛋通常用蛋杯盛放，蛋的顶部被刀或蛋剪刀切开，然后用一个茶勺把蛋挖出来就可以吃了。还有别的方法，比如用勺子轻敲蛋壳顶部。半熟蛋可以和切片黄油吐司一起吃，因为后者会浸没在流体状的蛋黄中。在英国，这样的切片吐司称为“士兵”。

煮得老的鸡蛋

老鸡蛋煮得比半熟蛋足够久，因而其蛋黄能凝结起来，可以趁热吃也可以做冷菜。它可以冷却后剁碎做蛋沙拉的料底，也可以趁热放入蛋杯内享用。

至于适合煮老鸡蛋的方法，这里有多种说法。一个是说把蛋和水一起烧开，煮8分钟。另一个说是水烧开后移开锅子停止加热，用水的余热继续煮蛋。还有人给出说法，说是把蛋放入沸水中加热一小会儿。

煮过头的蛋的蛋黄表面通常有薄薄的一层硫磺色的衣，为了避免这层衣的出现，人们常常在煮完蛋后把它浸没在冷水中，这样一来蛋白和蛋黄也会轻微收缩，剥起来更容易。

未剥壳的老鸡蛋可以放入冰箱中保存几天到几周。