One way to correct sentences is using online correction tools that are on websites such as GrammarCheck.net, OnlineCorrection.com and Reverso.net, as of July 2015. You can also use the Grammarly tool for free or as a premium user.
To check for errors at OnlineCorrection.com, simply paste into the field provided at the home page and click on the Check Text button. The tool marks words with grammar errors with red and grammar errors with green. To see suggestions the tool offers for improvement, move your mouse pointer over the marked words.
A similar procedure applies for Reverso.net and SpellCheckPlus.com. However, the tool at Reverso.net lets you choose between U.S. English and U.K. English. If you see green underlined text in the editor after running a check, it means the tool has automatically corrected erroneous text. If you see text highlighted in green, you need to click on the text to activate correction. If you see text highlighted in yellow, it means that the tool has encountered an unknown word for which it has no suggestion.
In addition to highlighting words with errors and offering suggestions, the tool at SpellCheckPlus.com offers explanations as to why the words are erroneous. The GrammarCheck.net tool offers a Deep Scan feature that redirects to the Grammarly website.