Web services for proof-reading can be a powerful tool if you know where to trust them and where better not. They can help you make your own text simpler, more straightforward and concise by offering simple corrections and checking for very basic mistakes (like using the same verb in consecutive sentences or using adverbs where they are superfluous.
Here is a short list of such services working in your browser:
Grammarly: “Grammarly makes you a better writer by finding and correcting up to 10× more mistakes than your word processor.” Very popular and lauded service with huge number of users. Find grammatical mistakes, contextual spelling errors and also highlights poor word usage. Also offers Chrome browser integration.
Hemingway Editor: Much simpler service meant for short texts. “The Hemingway Editor will highlight (in yellow and red) where your writing is too dense. Try removing needless words or splitting the sentence into two. Your readers will thank you.” It also gives your text a “readability” score.
Pro Writing Aid: Another comprehensive service that creates a report about the quality of your writing. It checks for consistency, complexity, vague words and alliterations among other things. The downside is that it is much more cluttered compared to Grammarly and also not very usable in its free version.
Paper Rater: This service offers grammar checks as well as plagiarism detection. Function-wise it falls a bit short compared to Grammarly or ProWritingAid.