These are the best 2020 chess programs, they are the strongest ones at the moment and you can download them for free. A Graphical User Interface (GUI) is required to use them, such as Fritz (Windows), the free Arena (Windows and Linux) or Droidfish (Android): any of these programs (chess engines) must be installed on said interfaces.
Stockfish Polyglot - Machines rapid competition and analysis (rated 9.21/10)
SugaR - Machines rapid competition and analysis
CorChess - Correspondence chess or long games (rated 9.02/10)
asmFish - Machines rapid competition (rated 8.54/10)
Cfish - Analysis but obsolete (on machines with many threads Stockfish 11 is better) (rated 9.15/10)
Brainfish - Machines rapid competition (rated 9.17/10)
Raubfisch - Machines rapid competition (rated 8.84/10)
How to install these program on Fritz: https://www.youtube.com/watch?v=Sohmt3X8ezs&feature=youtu.be.