The Bing Spell Check API offers suggestions for misspelled words, and contextual spell checking for text provided by a third party application. This is Microsoft's third generation spell-checker which does not rely on dictionaries, but on machine learning and statistical machine translation. Developers can integrate capabilities such as slang and informal language recognition, and homophones correction. Currently, a free plan that limits calls to 5000 transactions per month is available. This API uses JSON format for data exchange, and API Keys for authentication.