If so, Copyscape is a trusty tool to check for plagiarism. You can also check whether someone is lifting your own writing and passing it off as their work online.
You type in the website address or a couple of lines from the article and voila! Copyscape will detect where else it has appeared.
Here’s a wikihow post with instructions for using Copyscape:
It's no crime to do online research by reading other people’s work. It can give a content creator valuable information and the Internet makes it so darn easy. It’s the ultimate reference library at your fingertips.
It's what happens next that matters. A writer takes what they glean and mixes it with other information. They write their own take on the topic weaving together various facts, stories, interviews, angles, thoughts, insights, etc. to produce an original work.
Unfortunately at times for some, it is too easy to let “research” slide into “cut and paste” in whole or in part, producing an exact copy without giving the original writer credit or a link back to the main source.
When that occurs, whether the copying is accidental or intentional, Copyscape can help you sniff out a copycat. MEOW!