Streaming support

Both input and output bodies can be mapped to a stream, by using streamBody(streams). The parameter streams must implement the Streams[S] capability, and determines the precise type of the binary stream supported by the given non-blocking streams implementation. The interpreter must then support the given capability. Refer to the documentation of server/client interpreters for more information.


Here, streams refer to asynchronous, non-blocking, “reactive” stream implementations, such as akka-streams, fs2 or zio-streams. If you’d like to use blocking streams (such as InputStream), these are available through e.g. inputStreamBody without any additional requirements on the interpreter.

Adding a stream body input/output influences both the type of the input/output, as well as the 4th type parameter of Endpoint, which specifies the requirements regarding supported stream types for interpreters.

When using a stream body, the schema (needed for documentation) and format (media type) of the body must be provided by hand, as they cannot be inferred from the raw stream type. For example, to specify that the output is an akka-stream, which is a (presumably large) serialised list of json objects mapping to the Person class:

import sttp.tapir._
import sttp.capabilities.akka.AkkaStreams
import akka.util.ByteString

case class Person(name: String)

// copying the derived json schema type
endpoint.out(streamBody(AkkaStreams)(Schema(Schema.derived[List[Person]].schemaType), CodecFormat.Json()))

See also the runnable streaming example.