There is one website that does an OK grammar check of your writing. You just need to copy and paste the text into the text-box and off you go.
Note that it's an
OK grammar checker. It's not perfect. The checker on this site only uses US English, not UK, so if you use non-US Eng like I do when I write, you're spellings of certain words with come up wrong or not listed in its dictionary.
Also, don't rely on the site or its grammar checker, either, to proofread.
It does some weird stuff to certain words, especially when it suggests a replacement. It can and will mangle perfectly intelligible sentences.
If anything, just use it as a safety net to double check grammar after you've proof-read and or had a beta go through it.
The limit for text in this grammar checker is 1500 words too.
So it's really not useful for full-blown 5000+ word chapters, unless you break them down into sizeable chunks.
Site is here:
Online Grammar Checker
Again, don't rely on online grammar checkers to do what you should be doing yourself or getting a beta to do.
Use it as a writing tool, not as a last-ditch effort to avoid proofing at all.
The online grammar checkers aren't perfect, not by a long shot, and are about as useful as a spellchecker in Word.
~ Pyre