A microcache is a cache whose container is often too small to hold items other than a log book. If there are items in such caches, they tend to be very small items, such as coins. Frequently, the cache is not even large enough to hold its own writing utensil, containing only a small piece of paper where finders usually have room to write their name and a date.
Microcaches come in many differing types of containers. A common type would be a canister for 35-mm film rolls. Another common type would be magnetic key safes. As with regular-sized caches, the variety depends on the creativity of the hider.
Generally microcaches are hidden in locations where a regular-sized cache would not be easily hidden. Such locations may be parks that do not have sufficient hiding spaces for larger types. Often microcaches are used in urban settings, where there may exist only a small hidden spot. These are often called urban micros.
One of the elements that microcaches bring to geocaching is the extra challenge of locating it, as often the vicinity of the cache does not indicate the location of the cache. In many cases, the element of stealth is required as the cache may be hidden in a highly-trafficked spot, which adds to the challenge of locating the cache while non-cachers are present.
Microcaches are criticized by some geocachers as they tend to betray the principle of being able to exchange items. There are also criticism of microcaches as they sometimes are hidden in locations that are suitable for regular-sized caches. Another complaint is that microcaches often require very little preparation for hiding, thus allowing a geocacher to hide an inordinately high number of caches, versus those who take extra effort to prepare regular-sized caches.
Defenders of microcaches often cite that there exist many microcaches that are designed with detail and significant planning. They also argue that microcaches are usually hidden where a regular-sized cache would be inappropriate. Some argue that microcaches allow geocachers to have the extra challenge of microcache hunting versus hunting for regular-sized caches.