Can I use an HDRI to illuminate the scene and another one for the background?

Question

I want to illuminate my scene with an HDRI, and to use another one as a background image.

Answer 1

In the world shader, use the light path node to differentiate between the two.

Result with a white cube :

Answer 2

You can also do this through compositor.

1. Enable World transparency in Render > Film > Transparent
2. In Compositor, connect your new background image, and let alpha channel drive the visibility.
   Don't forget to check ✓ Use Nodes

Enable World transparency

The reflection comes from HDRi, the background comes from external image.