Docs.rs Streamlines Documentation Builds: Fewer Targets by Default Starting May 2026

Overview of the Upcoming Change

Effective May 1, 2026, docs.rs will modify its default build behavior to reduce the number of targets for which documentation is generated. Currently, unless a crate explicitly specifies a list of targets in its docs.rs metadata, the platform builds documentation for five default targets. After the change, only the default target will be built automatically. This adjustment refines a policy first introduced in 2020, when docs.rs enabled crate authors to opt into building fewer targets. The new default aligns with the fact that most crates do not contain target-specific code, making a single-target build sufficient for the majority of releases. Additionally, this change helps reduce build times and conserves resources on the docs.rs infrastructure.

Docs.rs Streamlines Documentation Builds: Fewer Targets by Default Starting May 2026 — Source: blog.rust-lang.org

The modification applies exclusively to new releases and rebuilds of existing releases. Previously published documentation remains unaffected.

How the Default Target Is Chosen

If you do not specify a custom default target in your crate’s docs.rs metadata, the system uses the architecture of its own build servers: x86_64-unknown-linux-gnu. This is a 64-bit Linux environment common in continuous integration setups.

Customizing the Default Target

You can override the default target by adding a default-target field in your Cargo.toml file under [package.metadata.docs.rs]. For example:

[package.metadata.docs.rs]
default-target = "x86_64-apple-darwin"

This instructs docs.rs to build documentation for macOS instead of the default Linux target. The default-target setting only applies when you do not define an explicit list of targets (see next section).

Building Documentation for Multiple Targets

If your crate requires documentation for more than one target—for instance, because it uses conditional compilation (#[cfg]) or platform-specific APIs—you must define the complete target list explicitly. Add a targets array in the same metadata section:

[package.metadata.docs.rs]
targets = [
    "x86_64-unknown-linux-gnu",
    "x86_64-apple-darwin",
    "x86_64-pc-windows-msvc",
    "i686-unknown-linux-gnu",
    "i686-pc-windows-msvc"
]

When targets is set, docs.rs builds documentation for exactly those targets—no more, no less. This gives you precise control over which platforms are documented. The platform still supports all targets available in the Rust toolchain; only the default behavior is changing.

Why You Might Need Multiple Targets

Crates that expose platform-specific functionality—such as low-level I/O on Windows vs. Linux—benefit from having documentation for each relevant target. Similarly, libraries targeting embedded systems or mobile platforms may need coverage for device-specific architectures. By listing targets explicitly, you ensure users see the correct documentation for their platform without unnecessary bloat.

Impact on Existing and New Crates

The change is backward-compatible in the sense that crates already using default-target or targets metadata will continue to work as before. Only crates that rely on the implicit five-target list will see a reduction. If your crate’s documentation currently builds for five targets and you want to maintain that behavior, simply copy the five-target list (as shown above) into your Cargo.toml before May 1, 2026.

We encourage all crate authors to review their documentation needs. If your code compiles identically across platforms, a single-target build is recommended—it reduces build time, saves server resources, and speeds up documentation publication.

Looking Ahead

This change is part of an ongoing effort to make docs.rs more efficient and responsive. By defaulting to a single target, the platform can allocate resources to more value-added features, such as faster rebuilds, better search, and more reliable uptime. Future improvements may include smart target selection based on actual use patterns.

Be sure to update your crate’s metadata by May 1, 2026 if you need the old behavior. As always, consult the docs.rs documentation for the latest guidelines.

Summary

Beginning May 1, 2026, docs.rs will build documentation for only the default target unless you specify a list of targets. The default target is x86_64-unknown-linux-gnu unless overridden with default-target. To build for multiple targets, use the targets array. This change makes the platform more efficient and aligns with the needs of most crate authors.

Tags: