Reply To: New Blur setting for HDRI

I assume you’re talking about the viewport shading under material preview?

The blur has been there a long time, but you’re right, it’s not under render preview. There you only have the option to adjust the opacity. 

If you want a blurred HDRI you’ll have to add it to the world shader and there you can add a white noise texture to the vector. With the factor you can then adjust the blur amount.