If you're looking to watch online, you can find it on various streaming platforms, including:
Ironically, pirating Interstellar ruins the film. Nolan shot Interstellar on 70mm IMAX film. The Blu-ray’s bitrate is massive. Filmyzilla compresses it into a 1.2GB file with: interstellar filmyzilla
However, I can offer you a to watching and understanding Interstellar : If you're looking to watch online, you can