Programming language: Rust
License: Apache License 2.0
Tags: Encoding     Yaml    
Latest version: v0.4.4

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The missing YAML 1.2 implementation for Rust.

Travis AppVeyor crates.io docs.rs

yaml-rust is a pure Rust YAML 1.2 implementation, which enjoys the memory safety property and other benefits from the Rust language. The parser is heavily influenced by libyaml and yaml-cpp.

Quick Start

Add the following to the Cargo.toml of your project:

yaml-rust = "0.4"

and import:

extern crate yaml_rust;

Use yaml::YamlLoader to load the YAML documents and access it as Vec/HashMap:

extern crate yaml_rust;
use yaml_rust::{YamlLoader, YamlEmitter};

fn main() {
    let s =
    - list1
    - list2
    - 1
    - 2.0
    let docs = YamlLoader::load_from_str(s).unwrap();

    // Multi document support, doc is a yaml::Yaml
    let doc = &docs[0];

    // Debug support
    println!("{:?}", doc);

    // Index access for map & array
    assert_eq!(doc["foo"][0].as_str().unwrap(), "list1");
    assert_eq!(doc["bar"][1].as_f64().unwrap(), 2.0);

    // Chained key/array access is checked and won't panic,
    // return BadValue if they are not exist.

    // Dump the YAML object
    let mut out_str = String::new();
        let mut emitter = YamlEmitter::new(&mut out_str);
        emitter.dump(doc).unwrap(); // dump the YAML object to a String
    println!("{}", out_str);

Note that yaml_rust::Yaml implements Index<&'a str> & Index<usize>:

  • Index<usize> assumes the container is an Array
  • Index<&'a str> assumes the container is a string to value Map
  • otherwise, Yaml::BadValue is returned

If your document does not conform to this convention (e.g. map with complex type key), you can use the Yaml::as_XXX family API to access your documents.


  • Pure Rust
  • Ruby-like Array/Hash access API
  • Low-level YAML events emission

Specification Compliance

This implementation aims to provide YAML parser fully compatible with the YAML 1.2 specification. The parser can correctly parse almost all examples in the specification, except for the following known bugs:

  • Empty plain scalar in certain contexts

However, the widely used library libyaml also fails to parse these examples, so it may not be a huge problem for most users.


  • Encoder
  • Tag directive
  • Alias while deserialization

Minimum Rust version policy

This crate's minimum supported rustc version is 1.31 (released with Rust 2018, after v0.4.3), as this is the currently known minimum version for regex as well.


Licensed under either of

at your option.


Fork & PR on Github.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

*Note that all licence references and agreements mentioned in the yaml-rust README section above are relevant to that project's source code only.