> The name *Nix* is derived from the Dutch word *niks*, meaning *nothing*;
> build actions do not see anything that has not been explicitly declared as an input.
>
> — <cite>[Nix: A Safe and Policy-Free System for Software Deployment](https://edolstra.github.io/pubs/nspfssd-lisa2004-final.pdf), LISA XVIII, 2004</cite>
The Nix logo is inspired by [an idea for the Haskell logo](https://wiki.haskell.org/File:Sgf-logo-blue.png) and the fact that [*nix* is Latin for *snow*](https://nix-dev.science.uu.narkive.com/VDaaP1BY/nix-logo).
The subject is considered controversial among Nix users and developers in terms of design, development processes, and community governance.
In particular:
- The RFC was closed without conclusion, and some design and implementation issues are not yet resolved.
Examples include the notion of a global [flake registry], the [impossibility of parameterising flakes](https://github.com/NixOS/nix/issues/2861), and the [new command line interface and flakes being closely tied to each other](https://discourse.nixos.org/t/2023-03-06-nix-team-meeting-minutes-38/26056#cli-stabilisation-announcement-draft-4).
- The original implementation introduced [regressions](https://discourse.nixos.org/t/nix-2-4-and-what-s-next/16257) in the [Nix 2.4 release](https://nixos.org/manual/nix/stable/release-notes/rl-2.4.html), breaking some stable functionality without a [major version](https://semver.org/) increment.
- New Nix users were and still are encouraged by various individuals to adopt flakes despite there being no concrete plan or timeline for stabilisation.
This led to a situation where the stable interface was only sparsely maintained for multiple years, and repeatedly suffered breakages due to ongoing development.
Meanwhile, the new interface was adopted widely enough for evolving its design without negatively affecting users to become very challenging.
As of the [2022 community survey](https://discourse.nixos.org/t/2022-nix-survey-results/18983), more than half of the user base, a third of which were relative beginners, relied on experimental features.
{term}`Nixpkgs` as a contrasting example, while featuring a `flake.nix` for compatibility, does not depend on Nix experimental features in its code base.
[Flakes](https://nix.dev/concepts/flakes) and the `nix` command suite bring multiple improvements that are relevant for both software users and package authors:
- The constraints imposed on flakes strengthen reproducibility by default, and enable various performance improvements when interacting with a large Nix package repository like {term}`Nixpkgs`.
- Flake references allow for easier handling of version upgrades for existing packages or project dependencies.
Other than that, and below the surface of the flake schema, Nix and the Nix language work exactly the same in both cases.
In principle, the same level of reproducibility can be achieved with or without flakes.
In particular, the process of adding software to {term}`Nixpkgs` or maintaining {term}`NixOS` modules and configurations is not affected by flakes at all.
Both paradigms have their own set of unique concepts and support tooling that have to be learned, with varying ease of use, implementation quality, and support status.
At the moment, neither the stable nor the experimental interface is clearly superior to the other in all aspects.
While flakes reduce complexity in some regards, they also introduce additional mechanisms and you will have to learn more about the system to fully understand how it works.
There are downsides to relying on [experimental features](https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-experimental-features) in general:
This may require you to adapt your code at some point in the future, which will be more effort when it has grown in complexity.
Currently there is no agreed-upon plan or timeline for stabilising flakes.
- The [Nix maintainer team](https://nixos.org/community/teams/nix.html) focuses on fixing bugs and regressions in stable interfaces, supporting well-understood use cases, as well as improving the internal design and overall contributor experience in order to ease future development.
- The [Nix documentation team](https://nixos.org/community/teams/documentation.html) focuses on improving documentation and learning materials for stable features and common principles.
[`*-small`](https://github.com/NixOS/nixpkgs/branches/all?query=-small) channel branches have passed a smaller test suite, which means they are more up-to-date with respect to their base branch but offer fewer stability guarantees.
Consult the [`nix-channel`](https://nixos.org/manual/nix/unstable/command-ref/nix-channel) entry in the Nix Reference Manual for more information on channels, and the [Nixpkgs contributing guide](https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md#branch-conventions) on the Nixpkgs branching strategy.
- binfmt interpreters, e.g., those configured with [`boot.binfmt.emulatedSystems`](https://search.nixos.org/options?show=boot.binfmt.emulatedSystems).
- Timing behaviour of the build system—parallel Make build does not get the correct inputs in some cases.
- Insertion of random values, e.g., from `/dev/random` or `/dev/urandom`.
- Differences between Nix versions. For instance, a new Nix version might introduce a new environment variable. A statement like `env > $out` is not promised by Nix to result in the same output, going into the future.