What a G-code diff can reveal
G-code describes motion, extrusion, temperature, cooling, and machine-specific behavior. A useful comparison can expose changed speeds, temperature commands, retraction moves, start code, or an unexpectedly different toolpath.
Normalization changes the answer
Slicers often regenerate timestamps, comments, whitespace, and N-line numbers. Ignore those when you care about executable instructions. Keep comments enabled when you are comparing slicer annotations or troubleshooting feature boundaries.
Read modifications in context
A changed command may represent a numeric adjustment on the same logical instruction. Added or removed rows often mean the toolpath structure itself changed. Check nearby temperature, fan, and motion commands before deciding whether a difference is harmless.
Large file limits
Full print jobs can contain millions of moves. PrintDiff calculates the full comparison but caps on-screen changed rows so the browser remains usable. Export the JSON summary when you need a machine-readable record.