Error

"invalid type" in Serde — How to Fix

Crates/Serde
2026-04-17T12:05:42+00:00
Fix Serde 'invalid type' errors by ensuring your Rust struct field names and types exactly match the incoming JSON data structure.

The "invalid type" error occurs because Serde cannot deserialize the incoming JSON data into your defined Rust struct, usually due to a mismatch in field names, data types, or missing fields. Ensure your struct field names match the JSON keys exactly (or use #[serde(rename = "...")]), that the Rust types align with the JSON values (e.g., String for text, i32 for integers), and that all non-optional fields are present in the JSON.

use serde::{Deserialize, Serialize};

#[derive(Debug, Deserialize, Serialize)]
struct User {
    name: String,
    age: i32,
}

fn main() {
    let json = r#"{"name": "Alice", "age": 30}"#;
    let user: User = serde_json::from_str(json).expect("Failed to parse");
    println!("{:?}", user);
}