JSON to Rust struct.

What the generator does

• Nested objects become their own structs, named from the key in PascalCase (address → Address, orders → Order).
• Arrays of objects are merged. Every item is read, not just the first. A key that some items have and others do not becomes Option<T>, so a missing field is a None instead of a deserialize error in production.
• null becomes Option. A key that is null in one place and a string in another becomes Option<String>. A key that is only ever null becomes Option<serde_json::Value>, because the JSON does not say what it holds.
• Numbers: whole numbers become i64 (u64 above the i64 range), anything with a decimal point becomes f64, and a key that is 7 in one item and 19.99 in another becomes f64. Mixed types (a string here, a number there) become serde_json::Value.
• Names: keys become snake_case fields. If every key in a struct is camelCase, you get one #[serde(rename_all = "camelCase")] instead of a rename on every field; otherwise each changed key gets #[serde(rename = "...")]. Rust keywords like type become raw identifiers (r#type), which serde reads and writes as plain type.
• Unknown fields: serde ignores JSON keys that are not in your struct by default (serde container attributes, checked Oct 23, 2026). Tick deny_unknown_fields to make them an error instead.

FAQ

How do I parse JSON into a struct in Rust?

Add serde (with the derive feature) and serde_json to Cargo.toml, paste your JSON above, copy the structs, then call let data: Root = serde_json::from_str(&text)?;. To read from a reqwest response, use resp.json::<Root>().await? (reqwest's json feature).

How do I handle a field that is sometimes missing?

Make it Option<T>. serde fills a missing Option field with None. This tool does it automatically when a key is missing from some items of an array or is null.

How do I map camelCase JSON keys to snake_case Rust fields?

Put #[serde(rename_all = "camelCase")] on the struct, or #[serde(rename = "userName")] on a single field. The generator picks the shorter of the two for each struct.

What if my JSON has a key named type?

type is a Rust keyword, so the field is written as r#type. serde strips the r# prefix, so it still matches the JSON key type.

Should I use f64 for money?

For display, f64 is fine. For arithmetic on money, parse into an integer number of cents or a decimal crate such as rust_decimal, because binary floats cannot represent most decimal amounts exactly.

Is my JSON sent to a server?

No. Parsing and code generation run in your browser. Nothing you paste leaves the page.