You can examine copy content from following sites, which are totally free. 1. Copyscape 2. WorldEssays Free Plagiarism Checker 3. Duplichecker 4. Plagiarisma
As you written here, same search in google find better result. You can use smallseotools for the best...
There are so many sites available online for duplicate content checker, some of them are: 1. SmallSeoTool 2. Dulichecker 3. Copyscape 4. Plagspotter 5. Seoreviewtools
Best free Duplicate content Checker Website: 1. Duplichecker 2. Seoreviewtools 3. Copyscape 4. Smallseotools 5. Plagiarisma 6. Dupeoff 7. Siteliner
I usually prefer to use Copyscape but it is a paid one. So, you can go with small seo tools plagiarism checker tool as it is a very good tool for checking duplicate content.