It is better to paste the text directly in "copyscape's" page using the premium account which is far better at detecting plagiarism than the "free" account. Copying each individual sentence of a 1000 words+ article would leave me weak and begging for soup.
You would copy paste the whole of the article into the textarea provided by copyscape (I think theres a max of 2000 words or something like that).
More Copyscape issues: Sometimes a Copyscape hit isn't proof of plagiarism. If you use a famous quote, it will probably cause a hit. I've seen it happen. As all my articles had to pass the Copyscape test, I had no choice but to remove the quoted sentence. Copyscape will sometimes think there's a hit even if the phrases aren't identical. If there's too many similar words in one sentence, it will flag it. If you re-arrange the sentence enough, then yes, it will pass. Unfortunately it can force honest writers into awkward writing just to avoid the hits. Yes, this is especially difficult for technical writing. I mean if you were to write a weight chart or a mathematical formula, how can you make it different? Copyscape does have its uses though. It sure is good enough to catch those lazy "writers" who think they can get away with the ol' copy-paste method.
Copyscape works great, when somebody post a duplicated content from any other website, Copyscpe detects it. If it doesn't show any other sites it means it has passed the content.
I am very skeptical about copyscape...I mean, just because it was one of the very first sites out there to check for duplicate content does not mean it is foolproof. The website itself is boring and tells you very little-no forum, nothing. I cannot even begin to imagine how copyscape can scan an article and then check the entire web for duplication in what, like 15 seconds? Impossible, I say. I would think that at least the developer would take some time to add to the site. I mean, hey, it costs me 5 cents to run one check there...I have to use it as EVERYONE depends on it and those nickles sure to add up when you are writing articles all day long.
You upload or copy paste the entire content and copyscape will prompt you if there are duplicate contents or not. I have been trying the learn the system used by copyscape and I have not been successful so far. But one thing good is that I never had problems with the contents that I have done since I begun my career as a freelance writer.