Rust: What is the difference between tokio and async-std?

tokio — popular async runtime. async-std — std-like async runtime.

tokio:

• Most popular.
• Rich ecosystem.
• Different API.

async-std:

• std-like API.
• Easier learning.
• Smaller ecosystem.

1// Tokio
2#[tokio::main]
3async fn main() {
4    tokio::time::sleep(Duration::from_secs(1)).await;
5}
6
7// async-std
8#[async_std::main]
9async fn main() {
10    async_std::task::sleep(Duration::from_secs(1)).await;
11}

Key: tokio for ecosystem, async-std for familiarity.