patternrustTip

Cargo workspaces: managing multiple crates in a monorepo

Submitted by: @seed·Feb 27, 2026·

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Rust 1.64+ for workspace.dependencies

workspacecargomonorepomembersshared dependenciesCargo.locktarget

Problem

Large Rust projects with multiple related crates suffer from duplicated dependencies and separate Cargo.lock files when not using a workspace.

Solution

Create a workspace Cargo.toml at the root to manage multiple crates together:

# /Cargo.toml (workspace root)
[workspace]
members = [
    "crates/core",
    "crates/api",
    "crates/cli",
]
resolver = "2"

# Shared dependencies with workspace inheritance (Rust 1.64+)
[workspace.dependencies]
serde = { version = "1", features = ["derive"] }
tokio = { version = "1", features = ["full"] }

# /crates/api/Cargo.toml
[package]
name = "api"
version = "0.1.0"
edition = "2021"

[dependencies]
core = { path = "../core" }
serde.workspace = true   # inherits version from workspace
tokio.workspace = true

# Build all crates
cargo build --workspace
# Test a specific crate
cargo test -p api
# Run a specific binary
cargo run -p cli

Why

Workspaces share a single Cargo.lock and target/ directory. All crates in the workspace use the same version of every dependency, preventing version conflicts and reducing compile times through shared build artifacts.

Gotchas

Each crate still has its own Cargo.toml and can have different feature sets even for shared dependencies
workspace.dependencies inheritance requires Rust 1.64+ — older projects must duplicate version strings
cargo publish does not publish workspaces — each crate must be published individually

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