Open the model on 0xr.space, press More in the dock, then Fix, and choose Smooth, Clean, Simplify, Mirror or Normals. The fix lands on the part you have picked, or on the whole model when nothing is picked, and a line names what happened, such as Smoothed or Normals rebuilt. More and Less run the last Smooth or Simplify again from where it started, stronger or weaker. It works in a browser, on an Android phone and in VR on Meta Quest, and runs on the device.
Smooth evens out bumps. Clean welds vertices that sit together, drops small loose pieces and fills holes. Simplify keeps about half the triangles. Mirror flips the mesh across its X axis. Normals rebuilds the shading from the faces. Keep as new, under Edit, saves the result as a new model on that device, and that model can be downloaded as GLB, STL or USDZ from its card's three-dot menu with a free account. Fix is not offered for Gaussian splats, and on a Quest a heavy model opens as a lighter copy that cannot be fixed.
Yes. Press Keep as new, then use Download GLB, Download STL or Download USDZ in the new model's three-dot menu on Home. Downloading needs a free account, signed into with a code sent to your email.
Often. It welds split corners and fills holes it can close. Keep the result and open Info on the copy to check.
Yes. Undo and Redo under Edit step through every edit and fix.
No. Fixes run on the device, and nothing is sent to a server unless you create a share link yourself.