A sphere in Minecraft is a stack of circles whose radii shrink as you leave the equator. This page does not guess those radii by eye. A block is in the shell when x² + y² + z² is greater than the inner radius squared and no greater than the outer radius squared. Thickness 1 keeps a hollow shell. A dome keeps the layers at Y ≥ 0, so you get a roof rather than a buried lower half. The slider moves one layer at a time, and the list shows every layer's block count before you dig or place anything.
Start a hollow sphere by marking the centre, then build the widest layer, which is the one nearest Y = 0. Its circle is the largest. As Y increases, the slice radius falls and the count falls with it. The top layer is a small cap, sometimes a single block. If your count at the top is dozens of blocks, you are still on a middle layer. Check the Y value in the note above the grid.
Domes are the practical version for bases and halls, because the lower hemisphere is either underground or in the way. Select dome and the negative Y layers disappear. The equator stays, so the dome's widest ring is still there to sit on a floor. A solid dome, thickness equal to the radius, is a hill of blocks rather than a roof. Use it for a filled planet prop, not for a room.
The PNG saves the layer you are looking at, not a 3D render. Export each important layer if you are building away from the screen. Circles on the ground, without the vertical stack, belong on the circle page. A stretched footprint belongs on the oval page; this sphere is round in all three axes.
Read the layer list before you place anything. Each row is a Y level and a block count. A thin sphere uses fewer blocks than a solid one of the same radius, and the list is how you budget the build. If the equator says 40 blocks and you have placed 28, you are not done with that layer, even if the ring "looks closed" from one side. Dome builders often start at Y = 0 so the widest circle is a floor plan they can walk. Sphere builders who want the bottom cap first should drag the slider to the lowest Y, place that small disc, and move up. The centre of every layer is the same column. Drift that column and the upper layers will not sit on the lower ones.
Radius is capped at 32. A thin sphere of that size is already a project, and the page is meant to be checked layer by layer rather than to dump a million-block schematic. There is no WorldEdit string and no downloadable structure file. The output is the grid, the counts, and the picture. Thickness on a sphere adds inner shells. A thickness of 2 is a wall you can stand under. A thickness equal to the radius fills the ball. Glass domes are still full blocks in the count. If you later swap the top layers for slabs, treat the count as the number of positions, not the number of slab items.