How Change Cycles background?

Hello
I use the Blender HDRI in Cycles but I have this grey background, do you know where to change it ?

World opacity slider in that very menu.

it makes the hdri appear, but it does not allow me to choose my color…

Sorry, I misunderstood.

1 Like

as simple as that, I’m ashamed :smiling_face:, thank you :pray: