# Nix [*Nix*][nix] can be a somewhat confusing term because it refers to multiple things: 1. The pure and functional [programming language][lang] 2. The [Nix CLI](#cli) 3. The overall Nix [package management system][package-management] All of these are closely interrelated and should be thought of as a single tool. In this document, we'll go over each of these three aspects of Nix. The Nix project is fully open source and largely developed within the [`NixOS`][nixos-org] organization on [GitHub]. It's licensed under [LGPL 2.1][license], which is generally quite permissive regarding commercial use. We at Determinate Systems have actively contributed to Nix as an open source project in the past—alongside countless talented individuals—and will continue to do so as part of our [mission] to make Nix better. We have also created [Determinate Nix][det-nix], a downstream distribution of Nix intended for enterprise. ## The Nix CLI \{#cli} There are two different Nix CLIs currently active: - The [unified Nix CLI](#unified-cli) is currently experimental but, from the standpoint of [Determinate Systems][ds], recommended for using Nix. It wraps all Nix functionality into a single `nix` executable and supports [flakes] - The [original Nix CLI](#original-cli), which is currently standard but, from the standpoint of [Determinate Systems][ds], _not_ recommended for using Nix. ### The unified CLI \{#unified-cli} The _unified CLI_ is a still-experimental way of using Nix that involves just one executable called `nix`. _All_ Nix functionality is wrapped into this tool, including commands like `nix build` for building [packages] instead of the old `nix-build` tool, `nix develop` for activating Nix [development environments][env] instead of the old `nix-shell` tool, `nix store` for managing the [Nix store][store] instead of the old `nix-store` tool, and more. Because the unified CLI isn't yet official, it needs to be explicitly enabled in your Nix configuration by adding `nix-command` to your `experimental-features` list. We won't cover setting up the unified CLI here because the [Determinate Nix Installer][install] both installs it and enables it in your Nix configuration. ### The original CLI \{#original-cli} The _original CLI_ for Nix is still the official CLI but, as we mention above, not recommended for new Nix users for two reasons: 1. It's incompatible with [Nix flakes][flakes] as it was created before the inception of flakes. 1. It presents significant cognitive overhead in comparison with the [unified CLI](#unified-cli) because it requires you to learn a wide variety of CLI tools, including `nix-build` for building [packages], `nix-shell` for Nix [development environments][env], `nix-store` for managing the [Nix store][store], and several more. The [Determinate Nix Installer][install] enables the [unified CLI](#unified-cli) by default, but leaves the tools from the original CLI accessible. [det-nix]: https://docs.determinate.systems/determinate-nix [ds]: https://determinate.systems [env]: /concepts/dev-env [flakes]: /concepts/flakes [github]: https://github.com [install]: /concepts/nix-installer [lang]: /concepts/nix-language [license]: https://github.com/nixOS/nix?tab=LGPL-2.1-1-ov-file [mission]: https://determinate.systems/posts/we-want-to-make-nix-better [nix]: https://nixos.org [nixos-org]: https://github.com/NixOS [packages]: /concepts/packages [package-management]: /concepts/package-management [store]: /concepts/nix-store