Use copyscape. It is a paid software, but it gives you a completely true result. The software lets you detect duplicate content and check if your articles are original.

Put content headline in Google, If that content is copied, It will show the exact results, otherwise your content is unique.

You can check it on Google search engine.

Let me get this straight. YOU don't know whether you are writing unique articles or not?
You don't know if you are plagiarizing them?

You people still do not know what the word plagiarism means.

Maybe it's just me, but I dang sure would know if I were plagiarizing anything.
And I would stop and try again.

I'm waiting for this question:

"So, can I walk into a bank, pull out a gun, get money from the teller with force,
and not be charged with bank robbery? Cuz I would really like to do that with
no problems. How do I know if I am robbing a bank?"

Paul

It's understandable that you would be worried about purchasing plagiarized articles/content. And, a few suggestions have already been made as to how to check to see if the article you have purchased was copied or stolen from another place.

I have heard about situations where some people will use a special code inside the document provided that makes it appear the article is unique.

One thing you should do before using any of the online plagiarism checkers is to copy the content from the original file and paste onto a notepad. The notepad will strip out any special codes. Next paste the text from the textpad into the checker.

I struggle between good content vs. just trying to make money.
Martin Kortyka