The Sandbox (Wikipedia:Sandbox) is a Wikipedia namespace page designed for testing and experimenting with Wiki syntax. Sandboxes in other languages can be found in a list on the English Sandbox, and the Meta-Wikipedia has a Sandbox at m:Meta:Sandbox. Also, since a Sandbox cannot be used for all forms of testing, there is an entire test Wikipedia available for use.
Different Wikipedias (and their Sandboxes) use different forms of character encoding. For example, meta and the French Wikipedia use UTF-8, while the English Wikipedia uses ISO 8859-1. As a result, the English Sandbox can be used by those who work in a UTF-8 environment to display the multi-character code of special characters. However, while using Sandboxes in other languages may be useful on certain occasions, it is important to keep in mind that, unless interwiki links are used, each Sandbox can only access the links, images, and templates on that particular Wikipedia.
The Sandbox was created as a place with fewer rules and policies than other pages on Wikipedia. For example, there is no need to follow the Manual of Style or reach community consensus before making a major change. However, it must not be used for malicious purposes, such as googlebombing, and rules such as no personal attacks and avoiding direct links to shock sites, which are never needed for testing, still apply. Also, please do not place offensive content in the sandbox.
If you are a registered member, you can create your own sandbox in your userspace. For example, if your username was JohnDoe, you could have your very own sandbox at User:JohnDoe/sandbox.
The term "Sandbox" is an Americanism for "Sandpit", and is the traditional name for free testing areas in Wiki projects and the like.