Async, await, and Futures in Rust
Answer: Futures are lazy and don't do anything until you use await. An async fn desugars to a function that returns a future of its return type.
Futures
A future represents an asynchronous computation commonly obtained by async. A future is a value that may not be ready now but will become ready later.
Claims
- id: C1 claim: Asynchronous programming is a core challenge covered in the Rust book. source: S1 evidence: "Asynchronous Programming: Async, Await, Futures, and Streams Many operations we ask the computer to do"
- id: C2 claim: Futures in Rust are lazy until you await them. source: S2 evidence: "futures in Rust are lazy: they don't do anything until you ask them to with"
- id: C3 claim: Writing async fn is equivalent to returning a future. source: S2 evidence: "writing async fn is equivalent to writing a function that returns a future of the"
- id: C4 claim: A future represents an asynchronous computation. source: S3 evidence: "A future represents an asynchronous computation, commonly obtained by use of async ."
Sources
- [S1] Fundamentals of Asynchronous Programming: Async, Await, Futures, and Streams. The Rust Project (The Rust Programming Language book). https://doc.rust-lang.org/book/ch17-00-async-await.html . License: MIT OR Apache-2.0. Accessed 2026-11-09.
- [S2] Futures and the Async Syntax. The Rust Project (The Rust Programming Language book). https://doc.rust-lang.org/book/ch17-01-futures-and-syntax.html . License: MIT OR Apache-2.0. Accessed 2026-11-09.
- [S3] Future trait. The Rust Standard Library. https://doc.rust-lang.org/std/future/trait.Future.html . License: MIT OR Apache-2.0. Accessed 2026-11-09.
License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted). Sources and notices: The Rust Programming Language book (rust-lang/book): Copyright (c) 2010 The Rust Project Developers; MIT OR Apache-2.0, used under MIT (https://github.com/rust-lang/book/blob/main/LICENSE-MIT). The Rust Standard Library docs (rust-lang/rust): Copyright (c) The Rust Project Contributors; MIT OR Apache-2.0, used under MIT (https://github.com/rust-lang/rust/blob/master/LICENSE-MIT). Text was condensed and changed from the originals.
License: CC-BY-4.0 · Summary by iinventedlight (AI-assisted). Sources: The Rust Project (The Rust Programming Language book), Fundamentals of Asynchronous Programming: Async, Await, Futures, and Streams, MIT OR Apache-2.0; The Rust Project (The Rust Programming Language book), Futures and the Async Syntax, MIT OR Apache-2.0; The Rust Standard Library, Future trait, MIT OR Apache-2.0. Notices: The Rust Programming Language book (rust-lang/book): Copyright (c) 2010 The Rust Project Developers; MIT OR Apache-2.0, used under MIT (https://github.com/rust-lang/book/blob/main/LICENSE-MIT). The Rust Standard Library docs (rust-lang/rust): Copyright (c) The Rust Project Contributors; MIT OR Apache-2.0, used under MIT (https://github.com/rust-lang/rust/blob/master/LICENSE-MIT).
Cite this
iinventedlight. 2026. "Async, await, and Futures in Rust." iinventedlight Library, iil:note:e0pzfjfg, version of 2026-11-09. https://iinventedlight.com/library/notes/rust-async-await-futures/. License: CC-BY-4.0.
@misc{iil_note_e0pzfjfg,
author = {{iinventedlight}},
title = {{Async, await, and Futures in Rust}},
howpublished = {iinventedlight Library},
year = {2026},
date = {2026-11-09},
url = {https://iinventedlight.com/library/notes/rust-async-await-futures/},
note = {Permanent ID iil:note:e0pzfjfg. License: CC-BY-4.0.},
}Spotted a mistake? Use the MCP feedback tool or email hello@iinventedlight.com.
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