This program is experimental and its interface is subject to change.


nix why-depends - show why a package has another package in its closure


nix why-depends [option...] package dependency


  • Show one path through the dependency graph leading from Hello to Glibc:

    # nix why-depends nixpkgs#hello nixpkgs#glibc
    └───bin/hello: …...................../nix/store/9l06v7fc38c1x3r2iydl15ksgz0ysb82-glibc-2.32/lib/ld-linux-x86-64.…
        → /nix/store/9l06v7fc38c1x3r2iydl15ksgz0ysb82-glibc-2.32
  • Show all files and paths in the dependency graph leading from Thunderbird to libX11:

    # nix why-depends --all nixpkgs#thunderbird nixpkgs#xorg.libX11
    ├───lib/thunderbird/libxul.so: …6wrw-libxcb-1.14/lib:/nix/store/adzfjjh8w25vdr0xdx9x16ah4f5rqrw5-libX11-1.7.0/lib:/nix/store/ssf…
    │   → /nix/store/adzfjjh8w25vdr0xdx9x16ah4f5rqrw5-libX11-1.7.0
    ├───lib/thunderbird/libxul.so: …pxyc-libXt-1.2.0/lib:/nix/store/1qj29ipxl2fyi2b13l39hdircq17gnk0-libXdamage-1.1.5/lib:/nix/store…
    │   → /nix/store/1qj29ipxl2fyi2b13l39hdircq17gnk0-libXdamage-1.1.5
    │   ├───lib/libXdamage.so.1.1.0: …-libXfixes-5.0.3/lib:/nix/store/adzfjjh8w25vdr0xdx9x16ah4f5rqrw5-libX11-1.7.0/lib:/nix/store/9l0…
    │   │   → /nix/store/adzfjjh8w25vdr0xdx9x16ah4f5rqrw5-libX11-1.7.0
  • Show why Glibc depends on itself:

    # nix why-depends nixpkgs#glibc nixpkgs#glibc
    └───lib/ld-2.31.so: …che       Do not use /nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31/etc/ld.so.cache.  --…
        → /nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31
  • Show why Geeqie has a build-time dependency on systemd:

    # nix why-depends --derivation nixpkgs#geeqie nixpkgs#systemd
    └───/: …atch.drv",["out"]),("/nix/store/qzh8dyq3lfbk3i1acbp7x9wh3il2imiv-gtk+3-3.24.21.drv",["dev"]),("/…
        → /nix/store/qzh8dyq3lfbk3i1acbp7x9wh3il2imiv-gtk+3-3.24.21.drv
        └───/: …16.0.drv",["dev"]),("/nix/store/8kp79fyslf3z4m3dpvlh6w46iaadz5c2-cups-2.3.3.drv",["dev"]),("/nix…
            → /nix/store/8kp79fyslf3z4m3dpvlh6w46iaadz5c2-cups-2.3.3.drv
            └───/: ….3.1.drv",["out"]),("/nix/store/yd3ihapyi5wbz1kjacq9dbkaq5v5hqjg-systemd-246.4.drv",["dev"]),("/…
                → /nix/store/yd3ihapyi5wbz1kjacq9dbkaq5v5hqjg-systemd-246.4.drv


Nix automatically determines potential runtime dependencies between store paths by scanning for the hash parts of store paths. For instance, if there exists a store path /nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31, and a file inside another store path contains the string 9df65igw…, then the latter store path refers to the former, and thus might need it at runtime. Nix always maintains the existence of the transitive closure of a store path under the references relationship; it is therefore not possible to install a store path without having all of its references present.

Sometimes Nix packages end up with unexpected runtime dependencies; for instance, a reference to a compiler might accidentally end up in a binary, causing the former to be in the latter's closure. This kind of closure size bloat is undesirable.

nix why-depends allows you to diagnose the cause of such issues. It shows why the store path package depends on the store path dependency, by showing a shortest sequence in the references graph from the former to the latter. Also, for each node along this path, it shows a file fragment containing a reference to the next store path in the sequence.

To show why derivation package has a build-time rather than runtime dependency on derivation dependency, use --derivation.


  • --all / -a Show all edges in the dependency graph leading from package to dependency, rather than just a shortest path.

  • --precise For each edge in the dependency graph, show the files in the parent that cause the dependency.

Common evaluation options:

  • --arg name expr Pass the value expr as the argument name to Nix functions.

  • --argstr name string Pass the string string as the argument name to Nix functions.

  • --debugger Start an interactive environment if evaluation fails.

  • --eval-store store-url The URL of the Nix store to use for evaluation, i.e. to store derivations (.drv files) and inputs referenced by them.

  • --impure Allow access to mutable paths and repositories.

  • --include / -I path Add path to the Nix search path. The Nix search path is initialized from the colon-separated NIX_PATH environment variable, and is used to look up the location of Nix expressions using paths enclosed in angle brackets (i.e., <nixpkgs>).

    For instance, passing

    -I /home/eelco/Dev
    -I /etc/nixos

    will cause Nix to look for paths relative to /home/eelco/Dev and /etc/nixos, in that order. This is equivalent to setting the NIX_PATH environment variable to


    It is also possible to match paths against a prefix. For example, passing

    -I nixpkgs=/home/eelco/Dev/nixpkgs-branch
    -I /etc/nixos

    will cause Nix to search for <nixpkgs/path> in /home/eelco/Dev/nixpkgs-branch/path and /etc/nixos/nixpkgs/path.

    If a path in the Nix search path starts with http:// or https://, it is interpreted as the URL of a tarball that will be downloaded and unpacked to a temporary location. The tarball must consist of a single top-level directory. For example, passing

    -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/master.tar.gz

    tells Nix to download and use the current contents of the master branch in the nixpkgs repository.

    The URLs of the tarballs from the official nixos.org channels (see the manual page for nix-channel) can be abbreviated as channel:<channel-name>. For instance, the following two flags are equivalent:

    -I nixpkgs=channel:nixos-21.05
    -I nixpkgs=https://nixos.org/channels/nixos-21.05/nixexprs.tar.xz

    You can also fetch source trees using flake URLs and add them to the search path. For instance,

    -I nixpkgs=flake:nixpkgs

    specifies that the prefix nixpkgs shall refer to the source tree downloaded from the nixpkgs entry in the flake registry. Similarly,

    -I nixpkgs=flake:github:NixOS/nixpkgs/nixos-22.05

    makes <nixpkgs> refer to a particular branch of the NixOS/nixpkgs repository on GitHub.

  • --override-flake original-ref resolved-ref Override the flake registries, redirecting original-ref to resolved-ref.

Common flake-related options:

  • --commit-lock-file Commit changes to the flake's lock file.

  • --inputs-from flake-url Use the inputs of the specified flake as registry entries.

  • --no-registries Don't allow lookups in the flake registries. This option is deprecated; use --no-use-registries.

  • --no-update-lock-file Do not allow any updates to the flake's lock file.

  • --no-write-lock-file Do not write the flake's newly generated lock file.

  • --output-lock-file flake-lock-path Write the given lock file instead of flake.lock within the top-level flake.

  • --override-input input-path flake-url Override a specific flake input (e.g. dwarffs/nixpkgs). This implies --no-write-lock-file.

  • --recreate-lock-file Recreate the flake's lock file from scratch.

  • --reference-lock-file flake-lock-path Read the given lock file instead of flake.lock within the top-level flake.

  • --update-input input-path Update a specific flake input (ignoring its previous entry in the lock file).

Logging-related options:

  • --debug Set the logging verbosity level to 'debug'.

  • --log-format format Set the format of log output; one of raw, internal-json, bar or bar-with-logs.

  • --print-build-logs / -L Print full build logs on standard error.

  • --quiet Decrease the logging verbosity level.

  • --verbose / -v Increase the logging verbosity level.

Miscellaneous global options:

  • --help Show usage information.

  • --offline Disable substituters and consider all previously downloaded files up-to-date.

  • --option name value Set the Nix configuration setting name to value (overriding nix.conf).

  • --refresh Consider all previously downloaded files out-of-date.

  • --repair During evaluation, rewrite missing or corrupted files in the Nix store. During building, rebuild missing or corrupted store paths.

  • --version Show version information.

Options that change the interpretation of installables:

  • --derivation Operate on the store derivation rather than its outputs.

  • --expr expr Interpret installables as attribute paths relative to the Nix expression expr.

  • --file / -f file Interpret installables as attribute paths relative to the Nix expression stored in file. If file is the character -, then a Nix expression will be read from standard input. Implies --impure.

Options to override configuration settings: