Types of caches
Current Cache Types
Note: Cache types should not be confused with cache sizes. Caches of any type can have containers of any size, and vice versa.
A traditional cache is the most common type of geocache, described in what is geocaching. It is a container of some sort containing a logbook. The coordinates of the container must be posted in the cache description.
A multi-cache involves two or more locations, the final location being a physical container. There are many variations, but most multi-caches have a hint or a set of coordinates to find the second "waypoint", and the second waypoint has hints or coordinates to the third, and so on.
An offset cache is a particular type of multi-cache. The coordinates for an offset cache are the location of an existing monument, plaque, or other object. Information on that object is used to calculate the coordinates of the cache container.
Mystery or Puzzle Caches
As the name might suggest, Puzzle Caches require you to solve a puzzle of some kind. Typically, the cache container is not at the posted coordinates, but is within a couple miles.
The Mystery/Puzzle type is a catch-all for caches that don't fit the other types for some reason. There are many creative variations.
Letterbox Hybrid Caches
Letterboxing is similar to geocaching. One difference is that the location of a letterbox is described with clues rather than with coordinates. Another difference is that those who find a letterbox record their discovery with rubber stamps: a personal stamp is used to mark a logbook in the letterbox, and a stamp in the letterbox is used to mark a personal logbook. Stamps for letterboxing are often hand-carved. The stamp in the letterbox is part of the letterbox, just like the logbook, and is not a trade item.
In some cases, the owner of a letterbox has listed it both as a letterbox and as a geocache. On the geocaching.com site, such caches are listed as letterbox hybrid caches. Groundspeak's guidelines require accurate GPS coordinates to be an integral part of the cache hunt. Some letterbox hybrids also use letterbox style clues (similar to a multi-cache or a mystery/puzzle cache). Others simply list the coordinates of the container (similar to a traditional cache).
An event cache is a set of coordinates along with a date and time to meet there. People can indicate on the website if they plan to attend, and log a "find" if they actually do. Event caches are great ways to meet people, trade hitchhikers, and swap caching stories.
CITO Event Caches
A CITO event cache is an event cache held specifically to clean up an area.
A mega-event cache is an event cache attended by at least 500 people.
Grandfathered Cache Types
Geocaching.com no longer allows new caches of the following types, but existing caches are grandfathered.
A virtual cache has no container or log book of any sort at the cache site. They can be created in locations where traditional caches cannot be placed. Geocachers find the location of a virtual cache and then prove that they were actually there by taking pictures of themselves and/or their GPSr or by answering specific questions about the location. Listing guidelines for virtual caches vary by listing site.
A webcam cache is a location with a public web cam. Finding the cache is locating the webcam and capturing from the cam a photograph of you. Webcams can have a photograph archive system from which to retrieve the photograph. If not, you will need to have someone watching the webcam on a computer to "capture" you at the location.
Locationless caches are sometimes referred to as "reverse" caches. In a locationless cache, the "hider" posts a description of a site without supplying coordinates. "Finders" try to find locations that match the description, and they post coordinates to those locations. Not all listing sites accept this kind of cache, but terracaching.com and GPSgames.org welcome locationless caches.
A traveling cache is a cache that travels from place to place. Before Groundspeak started selling and tracking travel bugs, a number of geocachers released physical caches that finders could pick up and move to a different location. A number of these caches are still active, but new traveling caches are no longer allowed to be listed on Geocaching.com. Other sites, such as GPSgames.org, welcome traveling caches. GPSgames.org even hosts a specialized geocaching GeoPoker game that features a traveling cache.
If a finder decides to move the cache to a new location, they are required to provide updated coordinates and sometimes a new hint. Some contain a logbook and a single item, such as an action figure or stuffed animal, that is supposed to stay in the cache. Depending on their size, they sometimes contain additional trade items.