Complexity Intelligence Spell Checking API analyzes a word or sentence depending on the service requested by the user. The user can have the API find single or multiple words that are candidates as possible correction of the word in input. It can also return the best correction to the string. It can correct multiple errors simultaneously. Complexity Intelligence is a start-up that focuses on Artificial Intelligence research. Complexity Intelligence is developing a range of natural language processing services accessible through web-services. Both free and paid subscriptions are available. Support is provided for both Java and PHP. The API uses RESTful protocol and responses are formatted in XML.