Do I always need to derive Serialize and Deserialize for Rust structs?

No, you only need Serialize and Deserialize derives when using that struct with serde_json. Derive Deserialize for structs you parse from JSON. Derive Serialize for structs you convert to JSON. Derive both if the struct goes both directions. Internal structs never exposed to JSON do not need these derives. Third-party crate types cannot have derives added—use custom serialization or wrapper types. Derives add compile-time code generation overhead but zero runtime cost. For generic structs, ensure all generic parameters implement required traits. Complex custom serialization logic requires manual Serialize/Deserialize implementations instead of derives. Use #[serde(skip)] on fields that should not serialize. Conditional compilation allows derives only when serde feature is enabled. Test your structs with our JSON Formatter at jsonconsole.com/json-formatter to verify serialization output. Derives are convenient and cover 95% of use cases. Only implement traits manually for complex requirements. Always derive rather than implement when possible for maintainability.