Swagger contains a OpenAPI / Swagger universal documentation generator and server handler.
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Swagger is low-level library which generate output compatible with Swagger / OpenAPI Spec 3.0.1, and wrapped many friendly APIs let developer understand and use it easier.


    github: icyleaf/swagger

Quick look

require "swagger"

builder = Swagger::Builder.new(
  title: "App API",
  version: "1.0.0",
  description: "This is a sample api for users",
  terms: "http://yourapp.com/terms",
  contact: Swagger::Contact.new("icyleaf", "icyleaf.cn@gmail.com", "http://icyleaf.com"),
  license: Swagger::License.new("MIT", "https://github.com/icyleaf/swagger/blob/master/LICENSE"),
  authorizations: [
    Swagger::Authorization.jwt(description: "Use JWT Auth"),

builder.add(Swagger::Controller.new("Users", "User resources", [
  Swagger::Action.new("get", "/users", "All users"),
  Swagger::Action.new("get", "/users/{id}", "Get user by id", parameters: [
    Swagger::Parameter.new("id", "path")
  ], responses: [
    Swagger::Response.new("200", "Success response"),
    Swagger::Response.new("404", "Not found user")
  Swagger::Action.new("post", "/users", "Create User", responses: [
    Swagger::Response.new("201", "Return user resource after created"),
    Swagger::Response.new("401", "Unauthorizated")

document = builder.built
p document


Structure in src directory:

├── xxx.cr                        # Friendly APIs
├── http                          # HTTP assets and libraries
└── objects                       # OpenAPI objects

Running on web

Swagger provids a built-in web server, if you have no idea how to preview it:

require "swagger"
require "swagger/http/server"

# made your document
document = builder.built

# Run web server


Swagger has two HTTP handlers which you can integrate it to mostly Crystal framework (like kemal, amber, lucky etc):

  • Swagger::HTTP::APIHandler
  • Swagger::HTTP::WebHandler


See more examples.


  • openapi
  • Info Object
  • Paths Object
    • PathItem Object
      • Parameter Object
      • RequestBody Object
      • Responses Object
      • Security Object
      • Tag Object
  • Tags Object
  • Servers Objec
    • ServerVariables Object
  • Security Object
  • Components Object
    • Schemas Object
    • SecuritySchemes Object
      • Basic
      • Bearer (include JWT)
      • APIKey
      • OAuth2
  • ExternalDocs Object


Swagger is a open source, collaboratively funded project. If you run a business and are using Swagger in a revenue-generating product, it would make business sense to sponsor Swagger development. Individual users are also welcome to make a one time donation if Swagger has helped you in your work or personal projects.

You can donate via Paypal.

How to Contribute

Your contributions are always welcome! Please submit a pull request or create an issue to add a new question, bug or feature to the list.

Here is a throughput graph of the repository for the last few weeks:

All Contributors are on the wall.

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MIT License © icyleaf