Rust Crate Registry

crates io is the official package registry for the Rust programming language, operated by the Rust Foundation and serving as the central hub for discovering, publishing, and distributing Rust libraries and tools known as crates. The registry has accumulated over 343 billion total downloads across 288,796 published crates as of 2026. The most downloaded crates include syn with 1.8 billion downloads, a parser for Rust source code used by procedural macros; hashbrown with 1.8 billion downloads, a Rust port of Google SwissTable hash map used as the standard library HashMap backend; getrandom with 1.5 billion downloads for cross-platform random number generation; bitflags with 1.4 billion downloads for generating bitflag structures; and libc with 1.3 billion downloads for raw FFI bindings to platform system libraries. Popular keywords on the platform include CLI with 13,244 crates, AI with 5,579 crates, async with 4,912 crates, parser with 4,072 crates, LLM with 3,668 crates, database with 3,438 crates, terminal with 3,348 crates, WebAssembly with 3,181 crates, and TUI with 3,142 crates. Popular categories include Development tools with 25,990 crates, Command line utilities with 25,485 crates, No standard library with 12,670 crates, Web programming with 12,281 crates, and Network programming with 11,337 crates. The registry integrates natively with Cargo, the Rust build tool and package manager, through the Cargo.toml manifest file and the cargo publish, cargo add, and cargo update commands. The platform provides a public JSON API for programmatic access to crate metadata, download statistics, version history, and dependency graphs, with rate limits of one request per second for anonymous access. The website source code is open source under the MIT and Apache 2.0 licenses, hosted on GitHub under the rust-lang organization.