PaperRater is described as 'Grammar & Spelling Check; Free Online Proofreading; No Downloads...Allows you to find those pesky mistakes and correct them before your teacher does'. There are more than 25 alternatives to PaperRater, not only websites but also apps for a variety of platforms, including Windows, Mac, Google Chrome and Android. The best alternative is Grammarly, which is free. Other great sites and apps similar to PaperRater are LanguageTool (Freemium, Open Source), Hemingway Editor (Paid), Ludwig.guru (Freemium) and ProWritingAid (Freemium).
Editor provides enhanced proofing tools for Office 365 subscribers. Behind the scenes, intelligent services identify spelling, grammar, and stylistic issues, and the Editor pane helps you understand suggestions so you can make choices that improve your writing.
PerfectIt is an MS Word add-in that helps you proofread your documents. It finds difficult-to-locate errors, improves your text, and saves you valuable time. PerfectIt works with US, UK, Canadian, Australian and all other international types of English.