Hemingway Editor is an app that helps you write clearly and succinctly. It tells you the grade level of your piece and it highlights areas that could use improvement. It’s also totally free.
Grammarly is an app that points out your grammar mistakes and makes suggestions for clarity and variety. It’s a great last step to take before publishing or sending your work to your editor, boss, or client. There’s a free version and an upgraded version, and the upgraded version includes a plagiarism check, which is a great tool for editors.
Noisli is a free app that plays all kinds of sounds in the background to keep you focused. You can even combine sounds and save them to make your own soundtrack. What’s more, there’s a timer for those who like the Pomodoro Technique for productivity, as well as a distraction-free blank page to write in (the blank page even changes colors, which is one of my favorite things about it).