We all must have seen movies where decapitation must have been carried out. Especially when it comes to was movies like Spactarcus, Game of thrones and into the Badlands. In general, movies that involves the use of swords in combat. We all know the decapitation is fake but sometimes they are made to appear so real that younger viewers are not allowed to see such movies.
Now here is logic behind it, they make use of graphics interchange format (GIF) The first half of the GIF would be the real actor, with a prosthetic skin flap on his chest that would hide the tube of blood that would spurt out of his neck area. The second half would be most likely a dummy, although it could have been CGI (Computer Generated imagery) or a combination of a dummy and CGI. There is always a cut in the film just before the head comes off but we would hardly notice it. This however depends on the type of editor in charge of the same. A top notch editor would edit it in a way that it would go unnoticed.
example of a prosthetic skin flap
An Example of CGI
News Hub Creator email@example.com