Is Mathf.PerlinNoise Improved or Classic?

Hey everyone. I’ve been doing research on Mathf.PerlinNoise, and Perlin Noise in general. After a lot of reading, I found out that the original algorithm (called ‘Classic Perlin Noise’) was later modified to address some issues, and the modified algorithm is called ‘Improved Perlin Noise’. In the documentation for Mathf.PerlinNoise, it doesn’t mention which version of the algorithm is being used; Classic or Improved.
Can anyone help me out with some info on this?
Thanks.

I’m reasonably confident it’s simplex noise. You don’t see Perlin noise very often anymore.

But why is the method named PerlinNoise then?