Grammarly, Online Spell Checker and WhiteSmoke are considered the three best online grammar checkers, according to PHPMatters.com. Grammarly takes the top position based on its powerful spell check and grammar tools.
Grammarly.com is a free online service that checks for over 250 grammar errors. Users access the service by creating an account and then logging in. Grammarly also offers a Google Chrome extension that allows the service to work with emails, with social networks such as Facebook and in offline word processing documents.
Online Spell Checker is part of Translated.net and spell checks for over 20 different languages. WhiteSmoke.com works on devices connected to the Internet such as cellphones, tablets, iPads and computers. It works with over 45 different languages.