rust-lang/cargo · error · anyhow::Error

unrecognized feature

Error message

unrecognized feature{} for crate {}: {}

What it means

Thrown by cargo add when the user requests features via --features or -F that do not exist on the target crate. The error message lists the unrecognized feature names, suggests close matches via edit-distance, and shows available features. The bail occurs at line 240 after the full message is assembled.

Solutions

1. Check the error message for suggested features via edit-distance matching
2. Review the 'available features' list printed in the error output
3. Inspect the crate's Cargo.toml or documentation to find valid feature names
4. Update the feature name to match an existing one

Example fix

# before
cargo add serde --features derrive
# error: unrecognized feature `derrive` for crate serde

# after — fix typo
cargo add serde --features derive

// Validate feature names before running cargo add
fn validate_features(crate_name: &str, requested: &[String]) -> Result<(), String> {
    // Fetch available features from the crate's metadata
    let output = std::process::Command::new("cargo")
        .args(["info", crate_name, "--format-version", "1"])
        .output().map_err(|e| e.to_string())?;
    let metadata: serde_json::Value = serde_json::from_slice(&output.stdout)
        .map_err(|e| e.to_string())?;
    let available: Vec<&str> = metadata["features"].as_object()
        .map(|m| m.keys().map(|s| s.as_str()).collect())
        .unwrap_or_default();
    for feat in requested {
        if !available.contains(&feat.as_str()) {
            return Err(format!("unrecognized feature `{feat}` for crate {crate_name}"));
        }
    }
    Ok(())
}

When it happens

Trigger: Running `cargo add foo --features bar` where 'bar' is not a feature defined in crate 'foo'. The unknown_features set is computed by diffing requested features against dep.available_features.

Common situations: Typo in a feature name. The feature was renamed or removed in a newer version of the crate. Confusing features from a different crate. Using crate-level features that are only available as dependency features.

Related errors

• cannot add ` ` as a dependency to itself
• cannot override workspace dependency with
• cannot specify a git URL
• cannot specify a path
• dependency ( ) specified without providing a local path…

AI-assisted analysis of rust-lang/cargo@98a09e7e7d (2026-08-11). Data as JSON: /api/errors/4850b3821417a768. Report an issue: GitHub.

Appendix: source

Thrown at src/ops/cargo_add/mod.rs:241

                                .map(|s| s.to_string())
                                .coalesce(|x, y| if x.len() + y.len() < 78 {
                                    Ok(format!("{x}, {y}"))
                                } else {
                                    Err((x, y))
                                })
                                .into_iter()
                                .format("\n    ")
                        )?;
                    } else {
                        writeln!(
                            message,
                            "\n\n{} enabled features available",
                            activated.len()
                        )?;
                    }
                }
            }
            anyhow::bail!(message.trim().to_owned());
        }

        print_dep_table_msg(&mut options.gctx.shell(), &dep)?;

        manifest.insert_into_table(
            &dep_table,
            &dep,
            workspace.gctx(),
            workspace.root(),
            options.spec.manifest().unstable_features(),
        )?;
        if dep.optional == Some(true) {
            let is_namespaced_features_supported =
                check_rust_version_for_optional_dependency(options.spec.rust_version())?;
            if is_namespaced_features_supported {
                let dep_key = dep.toml_key();
                if !manifest.is_explicit_dep_activation(dep_key) {
                    let table = manifest

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