nix-diff

Outputs human-readable differences between Nix derivations, including changes to inputs, environment variables, and build parameters, as shown in the NixOS example where adding a service alters the system derivation.

Specifically helps identify why Nix builds miss the binary cache by revealing exact derivation changes that trigger rebuilds, addressing a common pain point for Nix users.

Accepts various input types like derivation files, store paths, or symbolic links, allowing comparisons from different stages of the Nix build process, as demonstrated with nix-instantiate outputs and result symlinks.

Generates color-coded diff output that highlights changes clearly, improving readability over raw Nix data and making it easier to spot differences at a glance.