Cargo starts with a manifest file, typically Cargo.toml, which defines a package’s name, version, edition, dependencies, and build settings. For larger codebases, that metadata becomes the source of truth for how crates relate to one another and how Cargo should build them. Understanding package fields, dependency declarations, and targets is the foundation for organizing a Rust project beyond a single crate.
Manage Rust Projects with Cargo
Learn how Cargo organizes multi-package Rust codebases with manifests, dependencies, and workspaces.
Explore WorkspacesCargo manifests and package metadata
Core Cargo capabilities for larger codebases
Dependencies
Declare external crates and pin the versions your package needs. Cargo resolves them consistently so builds stay reproducible across environments.
Dev-dependencies
Keep test-only and example-only crates separate from production code. This helps reduce the runtime dependency set while still supporting development workflows.
Workspaces
Group multiple packages under one shared Cargo.toml configuration. Workspaces let related crates share target output, dependency resolution, and coordinated commands.
Crate structure
Split functionality into libraries, binaries, and supporting packages when a project grows. Clear crate boundaries make code easier to navigate and maintain.
Multi-package organization
Organize application code, shared libraries, and tools in one repository without turning everything into a single crate. This makes it easier to scale teams and reuse code.
Build, test, and run workspace members
Once a workspace is set up, Cargo can target the entire workspace or individual members. Use workspace-aware commands to build shared libraries, run a specific binary package, or test one member without touching the rest. In practice, that means you can iterate on a large Rust project with consistent dependency resolution while still focusing on the package you are actively changing.
Common questions about Cargo workspaces
What is the difference between a crate and a package?
A package is what Cargo manages through Cargo.toml, and it can contain one or more crates. A crate is the compilation unit Cargo builds, such as a library crate or a binary crate.
When should I use a workspace?
Use a workspace when you have multiple related packages that should share build output, dependency resolution, and command handling. It is especially useful for libraries plus binaries, or for applications split into reusable components.
Can workspace members have different dependencies?
Yes. Each member can define its own dependencies, while the workspace manages them together. Shared versions and common configuration are easier to coordinate when packages live in the same workspace.
How do dev-dependencies fit into a workspace?
Dev-dependencies are used for tests, examples, benchmarks, and other development-only code. They help keep production builds focused while still giving each member the tools it needs during development.
Do I need a workspace for every Rust project?
No. A single package is often enough for small projects. Workspaces become valuable when the codebase contains multiple crates that should be built and managed together.