JSON: Actix Web Documentation

# JSON Responses

APIs primarily communicate via JSON. Actix Web makes it trivial to return JSON objects using Serde.

#The web::Json Wrapper

If you return a struct wrapped in web::Json, Actix Web automatically serializes it and sets the Content-Type to application/json.

code_blocksrust

use actix_web::{get, web, Responder};
use serde::Serialize;

#[derive(Serialize)]
struct User {
    id: u32,
    name: String,
}

#[get("/user")]
async fn get_user() -> impl Responder {
    let user = User { id: 1, name: "Alice".to_string() };
    web::Json(user)
}

#Using HttpResponse::json()

Alternatively, you can use the json() method on an HttpResponseBuilder to specify status codes alongside your JSON data.

code_blocksrust

use actix_web::HttpResponse;

async fn error_resp() -> HttpResponse {
    HttpResponse::BadRequest().json(serde_json::json!({ "error": "Invalid Data" }))
}

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Reference Implementation

The following code snippet demonstrates the authoritative pattern for this documentation.

src/main.rs

Edition 2024

1use actix_web::{get, web, App, HttpServer, Responder};
2use serde::Serialize;
3 
4#[derive(Serialize)]
5struct Status {
6    healthy: bool,
7}
8 
9#[get("/health")]
10async fn health_check() -> impl Responder {
11    web::Json(Status { healthy: true })
12}
13 
14#[actix_web::main]
15async fn main() -> std::io::Result<()> {
16    HttpServer::new(|| App::new().service(health_check))
17        .bind(("127.0.0.1", 8080))?
18        .run()
19        .await
20}

JSON Responses

#The web::Json Wrapper

#Using HttpResponse::json()

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Reference Implementation

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