We all make mistakes when we write, and it would be nice if a computer could help us see the ones that spell checkers miss. Grammar checking is hard because language is squishy, making it difficult to simply write down the rules and check that they are followed. This lack of regularity is why grammar checkers have always been so poor. Fortunately, a new technique in machine learning called deep learning allows computers to be as squishy as our language, and effective grammar checking is finally possible.