OverType is described as 'is the over-the-top typewriter simulator. It's a straightforward, easy-to-use web app featuring several fonts reminiscent of real typewriters and adjustable sliders for Brokenness and Ribbon Ink'. There are three alternatives to OverType, not only websites but also apps for Mac and Windows. The best alternative is AHOY!, which is free. Other great sites and apps similar to OverType are Winston (Free) and Typewrite Something (Free).
Winston is the typewriter simulator for macOS. Perfect for one thing: Writing. Just writing. Without losing focus of your ideas, without the constant backtracking and endless fussing over your text, judging it too soon and killing your ideas dead!