Best Duplicate File Finder(windows 8.1)

"Best" is subjective.

There are a variety of products out there: free and for pay also.

One application may be really user friendly but full of bugs or poorly documented. Or a very stable product may still miss some duplicates.

The only way to really know is to try out various applications

Back up your system and download, only one at a time, an application that seems appropriate.

Be careful as many such applications want to change your configuration or otherwise load in some crapware products.

My approach is to first check for reviews and other verified user comments. Then go to the source site. At the first sign of any trickery e.g., any buttons etc. that appear to be the desired download but are actually not, I exit the site and do not go back.

In most cases you are going to have to make some tradeoffs: user friendly vs truly useful vs safe for your system.

Always a risk which such things. So do some "due diligence" (meaning look into that particular application) and if you are comfortable with the possible risks - down load and try the application.

Some products that were once good now are not. Other, newer products, could suit your requirements.

Try, carefully try, a couple of such applications. That is how you will find the answer suitable to you.