Yes, professional proofreaders do use Grammarly. Grammarly is a popular proofreading tool used by many experienced proofreaders who want to further improve their accuracy and ensure all the grammar rules are followed. Grammarly is popular because it offers automated checks for many of the most common grammar mistakes. It also offers suggestions to help users refine their writing style. Moreover, it has a wide variety of features that help detect errors such as spelling mistakes, stylistic issues, punctuation errors, and word choice. So, it can be said that professional proofreaders use Grammarly as it offers an all-in-one package to help them get their work done quickly and accurately.