serde

serde is the serialization framework most Rust services build on. It separates data shape (your types) from wire format (JSON, MessagePack, TOML, and more) through Serialize and Deserialize traits.

Recipe

[dependencies]
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"

use serde::{Deserialize, Serialize};
 
#[derive(Debug, Serialize, Deserialize)]
struct User {
    id: u64,
    email: String,
}
 
fn main() -> serde_json::Result<()> {
    let u = User { id: 1, email: "ada@acme.com".into() };
    let json = serde_json::to_string(&u)?;
    let back: User = serde_json::from_str(&json)?;
    assert_eq!(back.email, "ada@acme.com");
    Ok(())
}

When to reach for this:

• Any API boundary (HTTP, CLI output, config files)
• Database rows mapped to structs (with sqlx or sea-orm)
• Event payloads in queues or logs

Working Example

use serde::{Deserialize, Serialize};
 
#[derive(Serialize, Deserialize)]
struct Event {
    #[serde(rename = "event_type")]
    kind: String,
    #[serde(default)]
    retries: u32,
}
 
// Accepts {"event_type":"created"} without retries field
let e: Event = serde_json::from_str(r#"{"event_type":"created"}"#).unwrap();

What this demonstrates:

• Derive macros cover 90% of structs and enums
• Field attributes control naming and defaults
• Same type serializes to JSON, YAML, or bincode by swapping crates

Deep Dive

How It Works

• Traits - Serialize writes a type; Deserialize reconstructs it.
• Formats - serde_json, serde_yaml, toml, bincode are separate crates.
• Derive - #[derive(Serialize, Deserialize)] generates impls at compile time.
• Custom - #[serde(with = "module")] or manual impls for odd formats.

Cross-Link

For exhaustive coverage, see the dedicated serde basics section: custom serializers, enum tagging, and zero-copy patterns.

Gotchas

• Floating point in JSON - NaN and large integers may not round-trip. Fix: use strings or fixed-point types for money.
• Untagged enums - ambiguous when variants look alike. Fix: prefer #[serde(tag = "type")] for APIs.
• Large derives on hot paths - derive is fine; avoid serde_json::Value everywhere. Fix: typed structs at boundaries.
• Skipping deny_unknown_fields on public APIs - clients send typos silently. Fix: enable on request types.
• chrono vs time crate - pick one ecosystem-wide. Fix: standardize in workspace Cargo.toml.

Alternatives

FAQs

Related

• serde basics - full section
• JSON with serde_json - API payloads
• anyhow & thiserror - error types that serialize cleanly
• Essential Crates Best Practices - dependency hygiene

Stack versions: This page was written for Rust 1.97.0 (edition 2024), Tokio 1.x, Axum 0.8, serde 1.0, sqlx 0.8, clap 4, and Polars 0.46+.