1Checker is a free proofreading app with several tools to help perfect your English texts. 1Checker features a spell check, grammar check, style reviewer, vocabulary enrichment tool (basically a thesaurus), dictionary and translation tool all in one. 1Checker has a very simple and easy to use interface where you simply open a document within it or paste text, and then simply let 1Checker highlight your errors. You can apply all changes in a click or just apply those that you want to keep.