HTTP Clients (reqwest)

Call external HTTP APIs from Rust with reqwest - async requests, JSON, timeouts, and rustls TLS.

Recipe

Quick-reference recipe card - copy-paste ready.

let client = reqwest::Client::builder()
    .timeout(std::time::Duration::from_secs(10))
    .build()?;
 
let user: User = client
    .get("https://api.example.com/users/1")
    .bearer_auth(token)
    .send()
    .await?
    .error_for_status()?
    .json()
    .await?;

When to reach for this: Any Rust service integrating with REST webhooks, payment APIs, or internal microservices.

Working Example

use reqwest::StatusCode;
use serde::{Deserialize, Serialize};
 
#[derive(Serialize)]
struct CreateItem { name: String }
 
#[derive(Deserialize)]
struct Item { id: u64, name: String }
 
#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = reqwest::Client::builder()
        .timeout(std::time::Duration::from_secs(15))
        .user_agent("my-rust-service/1.0")
        .build()?;
 
    let created: Item = client
        .post("https://httpbin.org/post")
        .json(&CreateItem { name: "widget".into() })
        .send()
        .await?
        .error_for_status()?
        .json()
        .await?;
 
    let status = client.get("https://httpbin.org/status/404").send().await?;
    assert_eq!(status.status(), StatusCode::NOT_FOUND);
 
    Ok(())
}

What this demonstrates:

• Shared Client reused across requests (connection pooling).
• .json() for serde request and response bodies.
• error_for_status() turns 4xx/5xx into errors.
• Global timeout on the builder.

Deep Dive

How It Works

• reqwest uses hyper under the hood with Tokio.
• One Client per process maintains connection pool to hosts.
• Enable rustls-tls feature for TLS without OpenSSL.

Client Checklist

Rust Notes

// Reuse client in Axum State
#[derive(Clone)]
struct HttpClients { outbound: reqwest::Client }

Gotchas

• New Client per request - Destroys connection reuse. Fix: Build once at startup.
• No timeout - Hung upstream blocks worker forever. Fix: Always set timeouts.
• Ignoring error bodies - error_for_status drops useful JSON errors. Fix: Read body on failure for logging.
• TLS verify disabled - danger_accept_invalid_certs in prod. Fix: Proper CA bundle with rustls.
• Huge response bodies - json().await loads all into memory. Fix: Stream with bytes_stream.

Alternatives

FAQs

Related

• TLS with rustls - HTTPS setup
• Retries, Timeouts & Backoff - Resilience
• hyper - Lower level
• Networking Best Practices - Client rules
• Web Backends Basics - Server counterpart

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+.