It is extremely unlikely that the Universe is a simulation for a wide variety of reasons, foremost amongst them being expense. The level of simulation present in the Universe is sufficiently high that the only purpose of it would BE simulation, meaning that our physical laws would necessarily be quite close to the laws of whatever universe overlies us. However, this implies that building an Earth simulator with the level of fine-grained reality present here would be insanely expensive.

Ergo, it is highly unlikely that we are in a simulation because the amount of matter-energy necessary to generate said simulation is far in excess of any possible benefit for doing so.