The Sandbox Effect is a theory used to explain certain behaviors observed with some Internet search engines. The Sandbox Effect is the theory that websites with newly-registered domains or domains with frequent ownership or nameserver changes are placed in a sandbox (or holding area) in the indexes of Google until such time is deemed appropriate before a ranking can commence. Webmasters have noticed that their site will only show for keywords that are not competitive. It appears this effect does not affect new pages unless the domain is in the sandbox.

The Sandbox Effect is a topic of hot debate among those interested in search engines and search engine optimization. There are many different opinions about it, including the view that the Sandbox Effect doesn't actually exist and that the search ranking behavior can be explained as a result of a mathematical algorithm, rather than a decided policy.