G-code and 3MF thumbnails in Windows Explorer

What you see

• Text G-code (.gcode, .gco): the preview image your slicer wrote into the file's comments is decoded and shown.
• PrusaSlicer's binary G-code (.bgcode): its image blocks are read whole and the largest PNG wins. A file that carries only a QOI image is re-encoded for display.
• 3MF projects: the preview image stored in the package is shown.

Limits

• SageThumbs shows the picture the slicer saved. It does not draw the toolpath, so a file saved without an embedded picture has nothing to show.
• In OneDrive and other synced folders, files stored on the PC get thumbnails as anywhere else. Online-only files are left to the cloud app, since nothing is downloaded just to draw a thumbnail.

More you can do

• Plain STL, OBJ and PLY meshes carry no picture, so SageThumbs renders a shaded view: see STL thumbnails and OBJ and PLY thumbnails.

Extensions this covers

See every format SageThumbs 2K supports or browse all format guides.

Thumbnails not showing?

• Windows caches thumbnails, and a file it failed on once stays failed. In SageThumbs, Settings ▸ Advanced ▸ Rebuild thumbnail cache clears the cache and restarts Explorer.
• Make sure File Explorer's "Always show icons, never thumbnails" option is off, and that the format is ticked in SageThumbs Settings ▸ File types.
• Run st2k doctor in a terminal. It only reads, checks the whole chain, and prints a fix under anything that is wrong.

Related guides

• STL3D-print models, rendered as shaded thumbnails.
• OBJ and PLYMeshes from 3D apps and 3D scans, rendered shaded.
• Fusion 360 .f3dFusion 360 archives, from the preview packed inside.