23 releases (12 stable)

Uses new Rust 2021

2.4.2 Nov 23, 2022
2.2.0 Sep 24, 2022
1.1.0 Jun 10, 2022
0.2.0 Apr 18, 2022
0.1.0-beta6 Mar 7, 2022

#22 in Web programming

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Used in 3 crates



utoipa - Auto generated OpenAPI documentation

Utoipa build crates.io docs.rs MSRV

Want to have your API documented with OpenAPI? But you dont want to see the trouble with manual yaml or json tweaking? Would like it to be so easy that it would almost be like utopic? Don't worry utoipa is just there to fill this gap. It aims to do if not all then the most of heavy lifting for you enabling you to focus writing the actual API logic instead of documentation. It aims to be minimal, simple and fast. It uses simple proc macros which you can use to annotate your code to have items documented.

Utoipa crate provides auto generated OpenAPI documentation for Rust REST APIs. It treats code first appoach as a first class citizen and simplifies API documentation by providing simple macros for generating the documentation from your code.

It also contains Rust types of OpenAPI spec allowing you to write the OpenAPI spec only using Rust if auto generation is not your flavor or does not fit your purpose.

Long term goal of the library is to be the place to go when OpenAPI documentation is needed in Rust codebase.

Utoipa is framework agnostic and could be used together with any web framework or even without one. While being portable and standalone one of it's key aspects is simple integration with web frameworks.

Choose your flavor and document your API with ice cold IPA

Existing examples for following frameworks:

Even if there is no example for your favourite framework utoipa can be used with any web framework which supports decorating functions with macros similarly to warp and tide examples.

What's up with the word play?

The name comes from words utopic and api where uto is the first three letters of utopic and the ipa is api reversed. Aaand... ipa is also awesome type of beer 🍺.


  • default Default enabled features are json.
  • json Enables serde_json serialization of OpenAPI objects which also allows usage of JSON within OpenAPI values e.g. within example value. This is enabled by default.
  • yaml Enables serde_yaml serialization of OpenAPI objects.
  • actix_extras Enhances actix-web integration with being able to parse path and path and query parameters from actix web path attribute macros. See docs or examples for more details.
  • rocket_extras Enhances rocket framework integration with being able to parse path, path and query parameters from rocket path attribute macros. See docs or examples for more details.
  • axum_extras Enhances axum framework integration allowing users to use IntoParams without defining the parameter_in attribute. See docs or examples for more details.
  • debug Add extra traits such as debug traits to openapi definitions and elsewhere.
  • chrono Add support for chrono DateTime, Date and Duration types. By default these types are parsed to string types with additional format information. format: date-time for DateTime and format: date for Date according RFC3339 as ISO-8601. To override default string representation users have to use value_type attribute to override the type. See docs for more details.
  • time Add support for time OffsetDateTime, PrimitiveDateTime, Date, and Duration types. By default these types are parsed as string. OffsetDateTime and PrimitiveDateTime will use date-time format. Date will use date format and Duration will not have any format. To override default string representation users have to use value_type attribute to override the type. See docs for more details.
  • decimal Add support for rust_decimal Decimal type. By default it is interpreted as String. If you wish to change the format you need to override the type. See the value_type in component derive docs.
  • uuid Add support for uuid. Uuid type will be presented as String with format uuid in OpenAPI spec.
  • smallvec Add support for smallvec. SmallVec will be treated as Vec.
  • openapi_extensions Adds traits and functions that provide extra convenience functions. See the request_body docs for an example.
  • repr Add support for repr_serde's repr(u*) and repr(i*) attributes to unit type enums for C-like enum representation. See docs for more details.

Utoipa implicitly has partial support for serde attributes. See docs for more details.


Add minimal dependency declaration to Cargo.toml.

utoipa = "2"

To enable more features such as use actix framework extras you could define the dependency as follows.

utoipa = { version = "2", features = ["actix_extras"] }

Note! To use utoipa together with Swagger UI you can use the utoipa-swagger-ui crate.


Create a struct or it could be an enum also. Add ToSchema derive macro to it so it can be registered as an an OpenAPI schema.

use utoipa::ToSchema;

struct Pet {
   id: u64,
   name: String,
   age: Option<i32>,

Create a handler that would handle your business logic and add path proc attribute macro over it.

mod pet_api {
    /// Get pet by id
    /// Get pet from database by pet id
        path = "/pets/{id}",
            (status = 200, description = "Pet found succesfully", body = Pet),
            (status = 404, description = "Pet was not found")
            ("id" = u64, Path, description = "Pet database id to get Pet for"),
    async fn get_pet_by_id(pet_id: u64) -> Pet {
        Pet {
            id: pet_id,
            age: None,
            name: "lightning".to_string(),

This attribute macro substantially will create another struct named with __path_ prefix + handler function name. So when you implement some_handler function in different file and want to export this, make sure __path_some_handler in the module can also be accessible from the root.

Tie the Schema and the endpoint above to the OpenApi schema with following OpenApi derive proc macro.

use utoipa::OpenApi;

#[openapi(paths(pet_api::get_pet_by_id), components(schemas(Pet)))]
struct ApiDoc;

println!("{}", ApiDoc::openapi().to_pretty_json().unwrap());

This would produce api doc something similar to:

  "openapi": "3.0.3",
  "info": {
    "title": "application name from Cargo.toml",
    "description": "description from Cargo.toml",
    "contact": {
      "name": "author name from Cargo.toml",
      "email": "author email from Cargo.toml"
    "license": {
      "name": "license from Cargo.toml"
    "version": "version from Cargo.toml"
  "paths": {
    "/pets/{id}": {
      "get": {
        "tags": ["pet_api"],
        "summary": "Get pet by id",
        "description": "Get pet by id\n\nGet pet from database by pet id\n",
        "operationId": "get_pet_by_id",
        "parameters": [
            "name": "id",
            "in": "path",
            "description": "Pet database id to get Pet for",
            "required": true,
            "deprecated": false,
            "schema": {
              "type": "integer",
              "format": "int64"
        "responses": {
          "200": {
            "description": "Pet found succesfully",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Pet"
          "404": {
            "description": "Pet was not found"
        "deprecated": false
  "components": {
    "schemas": {
      "Pet": {
        "type": "object",
        "required": ["id", "name"],
        "properties": {
          "id": {
            "type": "integer",
            "format": "int64"
          "name": {
            "type": "string"
          "age": {
            "type": "integer",
            "format": "int32"

Go beyond the surface

  • See how to serve OpenAPI doc via Swagger UI check utoipa-swagger-ui crate for more details.
  • Browse to examples for more comprehensive examples.
  • Modify generated OpenAPI at runtime check Modify trait for more details.
  • More about OpenAPI security in security documentation.


Licensed under either of Apache 2.0 or MIT license at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, shall be dual licensed, without any additional terms or conditions.


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