Have you watched the show?

Penn and Teller know basically every technique there is. Fooling them usually boils down to did the magician effectively use multiple techniques in order to make them guess the wrong one that they used primarily, or if it's something where they know exactly what was used such as sleight of hand, if the magician is so skilled at sleight of hand that Penn and Teller don't see him doing it, aka they didn't "catch" him, they consider that fooling them even though they know how the trick is done in principle.

Fooling Penn and Teller, because they know the various ways any given trick could possibly be pulled off, more revolves around them correctly or incorrectly guessing the way or if their act was so flawless that they didn't in the moment see the method, they also reward the magician.

Many magicians have been on the show and say exactly how it works.

First they show the producers exactly how the trick works, and then they re-perform the tricks for Penn and Teller, and the producers via a mic confirms or denies that Penn and Teller's theory is correct or incorrect.

Now I'm sure there's some magicians they claim fooled them, that actually didn't, but because they liked the magicians act enough, they let on like they didn't fool them, but this is a rare case of a reality show that seems pretty legit.

Have you watched the show?

Penn and Teller know basically every technique there is. Fooling them usually boils down to did the magician effectively use multiple techniques in order to make them guess the wrong one that they used primarily, or if it's something where they know exactly what was used aka sleight of hand, if the magician is so skilled at sleight of hand that they don't see him doing it, aka they didn't "catch" him, they consider that fooling them even though they know how the trick is done in principle.

Fooling Penn and Teller, because they know the various ways any given trick could possibly be pulled off, more revolves around them correctly or incorrectly guessing the way or if their act was so flawless that they didn't in the moment see the method, they also reward the magician.