Crate ron

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Rusty Object Notation

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RON is a simple readable data serialization format that looks similar to Rust syntax. It’s designed to support all of Serde’s data model, so structs, enums, tuples, arrays, generic maps, and primitive values.


GameConfig( // optional struct name
    window_size: (800, 600),
    window_title: "PAC-MAN",
    fullscreen: false,
    mouse_sensitivity: 1.4,
    key_bindings: {
        "up": Up,
        "down": Down,
        "left": Left,
        "right": Right,
        // Uncomment to enable WASD controls
        "W": Up,
        "A": Down,
        "S": Left,
        "D": Right,
    difficulty_options: (
        start_difficulty: Easy,
        adaptive: false,

Why RON?

Example in JSON

   "materials": {
        "metal": {
            "reflectivity": 1.0
        "plastic": {
            "reflectivity": 0.5
   "entities": [
            "name": "hero",
            "material": "metal"
            "name": "monster",
            "material": "plastic"

Same example in RON

Scene( // class name is optional
    materials: { // this is a map
        "metal": (
            reflectivity: 1.0,
        "plastic": (
            reflectivity: 0.5,
    entities: [ // this is an array
            name: "hero",
            material: "metal",
            name: "monster",
            material: "plastic",

Note the following advantages of RON over JSON:

  • trailing commas allowed
  • single- and multi-line comments
  • field names aren’t quoted, so it’s less verbose
  • optional struct names improve readability
  • enums are supported (and less verbose than their JSON representation)

RON syntax overview

  • Numbers: 42, 3.14, 0xFF, 0b0110
  • Strings: "Hello", "with\\escapes\n", r#"raw string, great for regex\."#
  • Booleans: true, false
  • Chars: 'e', '\n'
  • Optionals: Some("string"), Some(Some(1.34)), None
  • Tuples: ("abc", 1.23, true), ()
  • Lists: ["abc", "def"]
  • Structs: ( foo: 1.0, bar: ( baz: "I'm nested" ) )
  • Maps: { "arbitrary": "keys", "are": "allowed" }

Note: Serde’s data model represents fixed-size Rust arrays as tuple (instead of as list)



ron = "0.8"
serde = { version = "1", features = ["derive"] }

use serde::{Deserialize, Serialize};

#[derive(Debug, Deserialize, Serialize)]
struct MyStruct {
    boolean: bool,
    float: f32,

fn main() {
    let x: MyStruct = ron::from_str("(boolean: true, float: 1.23)").unwrap();
    println!("RON: {}", ron::to_string(&x).unwrap());


VS Codea5huynh/vscode-ron
Sublime TextRON


There is a very basic, work in progress specification available on the wiki page. A more formal and complete grammar is available here.


RON is dual-licensed under Apache-2.0 and MIT.

Any contribution intentionally submitted for inclusion in the work must be provided under the same dual-license terms.


pub use de::from_str;
pub use de::Deserializer;
pub use error::Error;
pub use error::Result;
pub use options::Options;
pub use ser::to_string;
pub use ser::Serializer;
pub use value::Map;
pub use value::Number;
pub use value::Value;


Roundtrip serde Options module.

Value module.