The core sttp client API comes in a single jar, with a transitive dependency on sttp model. This also includes synchronous and [Future-based] backends, based on Java’s HttpClient.

To integrate with other parts of your application and various effect systems, you’ll often need to use an alternate backend, or backend wrappers (but what’s important is that the API remains the same!). See the section on backends for a short guide on which backend to choose, and a list of all implementations.

sttp client is available for Scala 2.12 and 2.13, as well as for Scala 3 and requires Java 11 or higher.

sttp client is also available for Scala.js 1.0 and Scala Native. Note that not all modules are compatible with these platforms, and that each has its own dedicated set of backends.

Using sbt

The basic dependency which provides the API, together with a synchronous and Future-based backends, is:

"com.softwaremill.sttp.client4" %% "core" % "4.0.0-M16"

Using scala-cli

Add the following directive to the top of your scala file to add the core sttp dependency:

//> using dep "com.softwaremill.sttp.client4::core:4.0.0-M16"

Using Ammonite

If you are an Ammonite user, you can quickly start experimenting with sttp by copy-pasting the following:

import $ivy.`com.softwaremill.sttp.client4::core:4.0.0-M16`


Working with sttp is most convenient if you import the sttp.client4 package entirely:

import sttp.client4._

This brings into scope the starting point for defining requests and some helper methods. All examples in this guide assume that this import is in place.

Synchronous requests

And that’s all you need to start using sttp client! To create and send your first request, import the above, type basicRequest. and see where your IDE’s auto-complete gets you! Here’s a simple request, using the synchronous backend:

import sttp.client4._

val backend = DefaultSyncBackend()
val response = basicRequest
  .body("Hello, world!")  


Creating a backend allocates resources (such as selector threads / connection pools), so when it’s no longer needed, it should be closed using .close(). Typically, you should have one backend instance for your entire application.

Serialising and parsing JSON

To serialize a custom type to a JSON body, or to deserialize the response body that is in the JSON format, you’ll need to add an integration with a JSON library. See json for a list of available libraries.

As an example, to integrate with the uPickle library, add the following dependency:

"com.softwaremill.sttp.client4" %% "upickle" % "4.0.0-M16"

Your code might then look as follows:

import sttp.client4._
import sttp.client4.upicklejson.default._
import upickle.default._

val backend = DefaultSyncBackend()

case class MyRequest(field1: String, field2: Int)
// selected fields from the JSON that is being returned by httpbin
case class HttpBinResponse(origin: String, headers: Map[String, String])

implicit val myRequestRW: ReadWriter[MyRequest] = macroRW[MyRequest]
implicit val responseRW: ReadWriter[HttpBinResponse] = macroRW[HttpBinResponse]

val request = basicRequest
  .body(MyRequest("test", 42))
val response = request.send(backend)

response.body match {
  case Left(e)  => println(s"Got response exception:\n$e")
  case Right(r) => println(s"Origin's ip: ${r.origin}, header count: ${r.headers.size}")

Adding logging

Logging can be added using the logging backend wrapper. For example, if you’d like to use slf4j, you’ll need the following dependency:

"com.softwaremill.sttp.client4" %% "slf4j-backend" % "4.0.0-M16"

Then, you’ll need to configure your client:

import sttp.client4._
import sttp.client4.logging.slf4j.Slf4jLoggingBackend

val backend = Slf4jLoggingBackend(DefaultSyncBackend())

Even quicker

You can skip the step of creating a backend instance, by using import sttp.client4.quick._ instead of the usual import sttp.client4._. This brings into scope the same sttp API, and additionally a synchronous backend instance, which can be used to send requests. This backend instance is global (created on first access), can’t be customised and shouldn’t be closed.

The send() extension method allows sending requests using that backend instance:

import sttp.client4.quick._

Next steps

Next, read on how sttp client works or see some examples.