Quick answer: Godot 4 export PCK checksum changing between identical builds? Build timestamps embedded in PCK - configure deterministic exports.
Two identical builds; itch.io accepts the first; rejects the second as duplicate.
Enable deterministic build
Export preset > Deterministic Build = on. Strips timestamps; identical inputs = identical outputs.
Or normalize timestamps
Pre-build, touch files with a fixed timestamp. Inputs deterministic.
Verify with hash
Hash the PCK after build; compare against previous. Mismatch = non-determinism.
“Default builds embed time. Deterministic mode strips.”
If your builds need to be reproducible (CI, delta uploads), the deterministic flag is mandatory.