How does serde_json serialize Vec<u8> into binary instead of an array?

[silence-coding]

How does serde_json serialize Vec into binary rather than an array? Serializing arrays takes up space exponentially.

use serde::{Serialize};
#[derive(Serialize)]
struct Test1{
    key: Vec<u8>
}
#[derive(Serialize)]
struct Test2{
    key: String
}

fn main() {
    let data = "xxxxxxxxxxxxxxxx";
    let test_vec = Test1 {
        key: data.as_bytes().to_vec(),
    };
    println!("{}", serde_json::to_vec(&test_vec).unwrap().len()); // 73

    let test2 = Test2 {
        key: data.to_string(),
    };
    println!("{}", serde_json::to_vec(&test2).unwrap().len()); //26
}

[dtolnay]

JSON does not have a binary data type. You would need to use a different format if you want binary bytes embedded into it.