Rust: What is the difference between tokio::spawn and spawn_local?

spawn — multi-threaded. spawn_local — single-threaded.

spawn:

• Runs on any thread.
• Requires Send.
• Multi-threaded runtime.

spawn_local:

• Runs on current thread.
• No Send requirement.
• Single-threaded runtime.

1// Multi-threaded
2tokio::spawn(async {
3    println!("Runs on any thread");
4});
5
6// Single-threaded
7tokio::task::spawn_local(async {
8    println!("Runs on current thread");
9});

Key: spawn for multi-threaded, spawn_local for single-threaded.