I have imported a file to make an HDRI in Blender 3d. I wanted to make the HDRI a little blurry so that there would be less harsh reflections.

The original file is about 500kb. After I apply a blur filter to it and export, the file is is almost 6000kb. I don't understand why.

I don't really know what file type the original file is (it was taken from the HDRI folder in Blender 3d) Windows just says "image" file

Anybody have experience with this?

I don't know about HDRI much but I guess It might be that when you blurred the image it created more colors and that increased the file size. It can be also that the original image was compressed and this was not.