Workspaces

Cargo workspaces group multiple packages with shared Cargo.lock and optional [workspace.dependencies].

Recipe

# Cargo.toml (root)
[workspace]
members = ["crates/api", "crates/cli"]
resolver = "2"
 
[workspace.dependencies]
serde = { version = "1.0", features = ["derive"] }
tokio = { version = "1", features = ["full"] }

When to reach for this: Monorepos with library + binary + internal crates sharing versions.

Working Example

# crates/api/Cargo.toml
[package]
name = "api"
version = "0.1.0"
edition = "2024"
 
[dependencies]
serde = { workspace = true }

cargo test --workspace
cargo build -p cli

What this demonstrates:

• Workspace dependency inheritance
• -p selects package
• Single lockfile for reproducible builds

Deep Dive

default-members for bare cargo build. exclude directories. Virtual workspace (no root package) common.

Gotchas

• Duplicate versions without workspace deps - Bloat. Fix: Centralize in workspace.dependencies.
• Publishing subset - Only publish leaf crates, not virtual manifest alone.
• path deps vs workspace - path = "../core" in members.
• feature unification - Resolver 2 unifies features across workspace.
• CI without --workspace - Misses member failures. Fix: cargo test --workspace.

Alternatives

FAQs

Related

• Cargo Workspaces
• Crates & Packages
• Feature Flags
• Workspace & Crate Boundaries

External Related Links

• The Cargo Book - Official guide and reference for Cargo.
• crates.io - Official crate registry.
• Rust Forge - Internal documentation for contributors and deeper ecosystem knowledge.
• Programming Rust, 2nd Edition (O'Reilly) - Same Programming Rust on O'Reilly.
• Rust for Rustaceans (Amazon) - Jon Gjengset.

Stack versions: This page was written for Rust 1.97.0 (edition 2024), Tokio 1.x, Axum 0.8, serde 1.0, sqlx 0.8, clap 4, and Polars 0.46+.