---
title: "Convert YAML to JSON and back"
url: https://recursiveai.org/oneyaml/rust/cookbook/yaml-to-json/
description: "Convert YAML to JSON with oneyaml and serde_json in Rust, convert JSON back to YAML, and get an error instead of a silent change for values JSON can’t hold."
version: "1.2.0"
---

# Convert YAML to JSON and back

Turn a YAML file into JSON, or JSON into YAML. oneyaml’s `serde_json` feature converts between `oneyaml::Value` and `serde_json::Value`.

```sh
cargo add oneyaml@1.2.0 -F serde_json
cargo add serde_json
```

```rust
use oneyaml::Value;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // YAML to JSON: read a Value, convert it (feature "serde_json").
    let yaml = "\
name: web
ports: [80, 443]
tls: true
owner: ~
";
    let v: Value = oneyaml::from_str(yaml)?;
    let json = serde_json::Value::try_from(&v)?;
    println!("{}", serde_json::to_string_pretty(&json)?);

    // JSON to YAML: JSON is valid YAML 1.2, so read it and write YAML.
    let text = r#"{"name": "web", "ports": [80, 443], "env": {"LOG": "info"}}"#;
    let v: Value = oneyaml::from_str(text)?;
    print!("{}", oneyaml::to_string(&v)?);

    // Values with no JSON form are an error with a path, not a silent change.
    let v: Value = oneyaml::from_str("ratio: .nan\n")?;
    println!("{}", serde_json::Value::try_from(&v).unwrap_err());
    Ok(())
}
```

```text
{
  "name": "web",
  "owner": null,
  "ports": [
    80,
    443
  ],
  "tls": true
}
name: web
ports:
  - 80
  - 443
env:
  LOG: info
float .nan has no JSON form (JSON numbers are finite) at ratio
```

## Good to know

- **No silent coercion.** What JSON can’t hold is an error with its path: tags, non-string keys, `.nan` and `.inf`, integers beyond 64 bits, and nesting past 128 levels. `Value::to_json_with` lists them all.
- The JSON keys above come out sorted because `serde_json::Value` sorts them by default. Turn on `serde_json`’s `preserve_order` feature to keep the file’s order.
- JSON is valid YAML 1.2, so `oneyaml::from_str` reads JSON text directly. The YAML written uses block style.
- For typed data, skip `Value`: read into your struct with `oneyaml::from_str` and write it with `serde_json::to_string`.