The Microsoft Azure Cognitive Services 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. This API uses JSON format for data exchange, and API Keys for authentication. Free trial API keys are available here.