How to Prepare Your Crate for docs.rs‘s New Default Target Behavior

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<h2>Introduction</h2> <p>Starting <strong>2026-05-01</strong>, docs.rs will change its default build behavior. Currently, if your crate’s <code>Cargo.toml</code> does not specify a targets list in the <code>[package.metadata.docs.rs]</code> section, docs.rs builds documentation for <em>five</em> default targets. After that date, it will build only for the default target unless you explicitly ask for more.</p><figure style="margin:20px 0"><img src="https://www.rust-lang.org/static/images/rust-social-wide.jpg" alt="How to Prepare Your Crate for docs.rs‘s New Default Target Behavior" style="width:100%;height:auto;border-radius:8px" loading="lazy"><figcaption style="font-size:12px;color:#666;margin-top:5px">Source: blog.rust-lang.org</figcaption></figure> <p>This change is the next step in an opt-in system first introduced in 2020. The reasoning is simple: most crates compile identically across targets, so building fewer targets by default saves build time and server resources. It also makes your documentation updates faster.</p> <p><strong>Who is affected?</strong> This change affects:</p> <ul> <li>New releases of any crate</li> <li>Rebuilds of old releases</li> </ul> <p>If you already have a <code>targets</code> list set, nothing changes for you. If you rely on the defaults, read on.</p> <h2>What You Need</h2> <ul> <li>A Rust crate with a <code>Cargo.toml</code> file</li> <li>Understanding of your crate’s platform-specific code (if any)</li> <li>Knowledge of which targets are relevant for your users</li> <li>Access to docs.rs (to verify builds after changes)</li> </ul> <h2>Step-by-Step Guide</h2> <h3 id="step1">Step 1: Understand the Default Target</h3> <p>If you do not set <code>default-target</code> in your docs.rs metadata, the default target is <code>x86_64-unknown-linux-gnu</code> (the same as the build server). This is a sensible default for most crates because Linux is the most common platform for documentation consumption.</p> <p>However, you can change it to any target supported by the Rust toolchain. For example, if your crate is primarily used on macOS, you might override it.</p> <h3 id="step2">Step 2: Check Your Current Configuration</h3> <p>Open your <code>Cargo.toml</code> and look for a <code>[package.metadata.docs.rs]</code> section. If it exists, check whether you have a <code>targets</code> key. If you do, you are already opted in and can skip the rest. If not, you are currently relying on the old default five targets.</p> <p>If the section is missing entirely, you are also relying on the defaults.</p> <h3 id="step3">Step 3: Decide If You Need Multiple Targets</h3> <p>Ask yourself: does your crate compile different code on different platforms? Common reasons include:</p> <ul> <li>Using conditional compilation with <code>cfg</code> attributes (e.g., <code>#[cfg(target_os = "windows")]</code>)</li> <li>Providing platform-specific APIs or re-exports</li> <li>Having dependencies that vary by target</li> </ul> <p>If your crate is entirely cross-platform without conditional compilation, building for one target is likely sufficient. If you do have platform-specific code, you probably want documentation for multiple targets so that users on each platform can see the correct API.</p> <h3 id="step4">Step 4: Set a Default Target (Optional)</h3> <p>If you only need documentation for one target, you can either stick with the default (Linux) or override it. To override, add this to your <code>Cargo.toml</code>:</p> <pre><code>[package.metadata.docs.rs] default-target = "x86_64-apple-darwin"</code></pre> <p>Replace the target triple with the one you prefer. This is useful if your primary audience uses a specific platform.</p> <h3 id="step5">Step 5: Define an Explicit Targets List</h3> <p>If you need documentation for more than one target, provide the full list in your <code>Cargo.toml</code>:</p> <pre><code>[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" ]</code></pre> <p>When <code>targets</code> is set, docs.rs will build documentation for exactly those targets – no more, no less. You can use any target from the Rust toolchain.</p> <h3 id="step6">Step 6: Test Your Configuration (Optional)</h3> <p>While you can’t directly trigger a docs.rs build on demand, you can:</p> <ul> <li>Run <code>cargo doc</code> locally for each target you intend to support (using <code>--target</code>) and verify that the documentation renders correctly.</li> <li>Push a new release to crates.io after making changes, then check the resulting docs.rs page.</li> </ul> <h3 id="step7">Step 7: Prepare for the Deadline</h3> <p>The change takes effect on <strong>2026-05-01</strong>. Before that date:</p> <ul> <li>If you want to keep the current behavior (five targets), add an explicit <code>targets</code> list as shown in Step 5.</li> <li>If you are happy with only one target, you can do nothing (but consider setting <code>default-target</code> if the default Linux target isn’t ideal).</li> <li>For crates that need multiple targets but have no <code>targets</code> list, you <em>must</em> add one to avoid losing documentation for those platforms.</li> </ul> <h2>Tips</h2> <ul> <li><strong>Keep it simple:</strong> If your crate has no conditional compilation, stick with the default target. It reduces build time and resource usage.</li> <li><strong>Use a smaller targets list:</strong> Instead of the old five, consider just two or three major platforms (Linux, macOS, Windows). Many crates don’t need i686 anymore.</li> <li><strong>Check your dependencies:</strong> Sometimes platform-specific behavior comes from dependencies. Review their docs too.</li> <li><strong>Monitor after the change:</strong> After May 1, 2026, check your docs.rs page after a release to ensure it builds as expected.</li> <li><strong>Document your choice:</strong> Add a comment in your <code>Cargo.toml</code> explaining why you chose certain targets – helpful for collaborators.</li> </ul> <p>By following these steps, you can seamlessly adapt to docs.rs’s new default behavior and ensure your crate’s documentation remains accessible to your users on all platforms they need.</p>