FVM vs Nix

FVM manages Flutter SDK versions by project, allowing teams to keep builds consistent while using different versions across projects. A project’s `.fvmrc` file records its selected Flutter version and can include project-specific settings and flavors. FVM switches among installed SDKs without downloading them again. It can identify unreferenced versions, preview cleanup candidates, and remove unused SDKs with `fvm cleanup`. The documentation describes commands suitable for CI/CD automation and support for custom Flutter repositories. FVM provides packages for macOS, Linux, and Windows, with architecture availability varying by system. Installation options include a shell script, Homebrew, Chocolatey, Pub, and standalone packages. FVM detects VS Code and updates `.vscode/settings.json` for the Dart Code extension to use the project’s managed SDK. Android Studio and IntelliJ settings must be configured separately to point to the FVM SDK path. JSON API commands expose installed SDKs, releases, cleanup data, environment context, and project configuration. FVM stores known project roots in a machine-local file and says it does not scan disks for projects. The project is licensed under MIT.

Nix is a free package management and system configuration tool for creating reproducible, declarative systems. It builds packages in isolation to avoid undeclared dependencies and help keep builds consistent across machines. Users can define and share development and build environments across projects and languages, install software from URLs or source code, and use virtual machines for integration testing. Nix supports dependency resolution, lockfiles, workspaces and offline installation; its package formats include Nix expressions, derivations and flakes. The Nix Packages collection offers over 140,000 packages. The wider ecosystem supports remote builds and deployments, binary caches, cross compilation, atomic upgrades and rollbacks to earlier package versions. Nix runs on Linux and macOS, and on Windows through WSL2; multi-user Windows installation requires WSL systemd support. Documentation includes guides for GitHub Actions, Docker images, Terraform deployment, SSH provisioning and distributed builds. Nix is aimed at people familiar with command-line interfaces and plain-text editors, including developers, test engineers, DevOps engineers, system administrators, data scientists, students and open-source enthusiasts. It has no paid plan listed.