Why is my hdri background image renders with low quality?

I used hdri image from blender file but it appears with low pixel, i had reinstalled blender but it still looks like this…

It depends on the resolution of the HDRI image.

You can always replace it with a better one, HDRI haven has a ton of good ones.

Be aware that higher resolution ones can slow down Blender depending on your PC specs.

So in short, it’s an image’s problem, isn’t?

You need to use a much higher resolution HDRI. Lower resolution ones can be perfectly fine for lighting and even reflections, but not if they will be seen in the background.

That’s a reasonable size one, yet you can still see that the resolution of the part seen by camera is lower than the default render size,

Pretty much.

6912p X 3456p… OMG that a huge one, thanks!

Thank you!

The default camera in Blender has a field of view of 39.6 degrees. The default render dimension is 1920px wide. 360 degrees divided by 36.9 degrees is about 9. 1920 x 9 = 17,280. So, in theory you’d need an HDRI that was about 17K for maximum background quality. A camera with a focal length of less than 50mm would require less and a camera with a focal length of higher than 50mm would require more.

In practice 1K HDRIs are perfectly good for positioning and testing and 4K or 8K ones can often be good enough for rendering. People’s eyes should be drawn to the subject of your scene.

HDRI Haven tends to have 1K, 2K, 4K, 8K, 16K and 20K versions for each HDRI

The one I used in my example is a 7K one from here: https://www.maximeroz.com/hdri-free-pack