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tapir, or Typed API descRiptions

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With tapir, you can describe HTTP API endpoints as immutable Scala values. Each endpoint can contain a number of input parameters, error-output parameters, and normal-output parameters. An endpoint specification can be interpreted as:

  • a server, given the "business logic": a function, which computes output parameters based on input parameters. Currently supported:
  • a client, which is a function from input parameters to output parameters. Currently supported:
  • documentation. Currently supported:


import sttp.tapir._
import sttp.tapir.json.circe._

type Limit = Int
type AuthToken = String
case class BooksFromYear(genre: String, year: Int)
case class Book(title: String)

// Define an endpoint

val booksListing: PublicEndpoint[(BooksFromYear, Limit, AuthToken), String, List[Book], Any] = 
    .in(("books" / path[String]("genre") / path[Int]("year")).mapTo[BooksFromYear])
    .in(query[Limit]("limit").description("Maximum number of books to retrieve"))

// Generate OpenAPI documentation

import sttp.tapir.openapi.circe.yaml._

val docs = OpenAPIDocsInterpreter().toOpenAPI(booksListing, "My Bookshop", "1.0")

// Convert to akka-http Route

import sttp.tapir.server.akkahttp.AkkaHttpServerInterpreter
import akka.http.scaladsl.server.Route
import scala.concurrent.Future

def bookListingLogic(bfy: BooksFromYear,
                     limit: Limit,
                     at: AuthToken): Future[Either[String, List[Book]]] =
  Future.successful(Right(List(Book("The Sorrows of Young Werther"))))
val booksListingRoute: Route = AkkaHttpServerInterpreter()
  .toRoute(booksListing.serverLogic((bookListingLogic _).tupled))

// Convert to sttp Request

import sttp.tapir.client.sttp.SttpClientInterpreter
import sttp.client3._

val booksListingRequest: Request[DecodeResult[Either[String, List[Book]]], Any] = 
    .toRequest(booksListing, Some(uri"http://localhost:8080"))
    .apply((BooksFromYear("SF", 2016), 20, "xyz-abc-123"))


tapir documentation is available at

Quickstart with sbt

Add the following dependency:

"com.softwaremill.sttp.tapir" %% "tapir-core" % "0.20.0-M6"

Partial unification is now enabled by default from Scala 2.13. However, if you're using Scala 2.12 or older, then you'll need partial unification enabled in the compiler (alternatively, you'll need to manually provide type arguments in some cases):

scalacOptions += "-Ypartial-unification"

Then, import:

import sttp.tapir._

And finally, type endpoint. and see where auto-complete gets you!

Sidenote for scala 2.12.4 and higher: if you encounter an issue with compiling your project because of a StackOverflowException related to this scala bug, please increase your stack memory. Example:

sbt -J-Xss4M clean compile

Other sttp projects

sttp is a family of Scala HTTP-related projects, and currently includes:

  • sttp client: the Scala HTTP client you always wanted!
  • sttp tapir: this project
  • sttp model: simple HTTP model classes (used by client & tapir)


Tapir is an early stage project. Everything might change. All suggestions welcome :)

See the list of issues and pick one! Or report your own.

If you are having doubts on the why or how something works, don't hesitate to ask a question on gitter or via github. This probably means that the documentation, scaladocs or code is unclear and be improved for the benefit of all.

Testing locally

The JS tests use Gecko instead of Chrome, although this causes another problem: out of memory when running JS tests for multiple modules. Work-arounds:

  • run only JVM tests using testJVM
  • test single JS projects
  • use CI (GitHub Actions) to test all projects - the .github/workflows/ci.yml enumerates them one by one

You can test only server/client/doc/other projects using testServers, testClients, testDocs and testOther.

Commercial Support

We offer commercial support for tapir and related technologies, as well as development services. Contact us to learn more about our offer!


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