Binary data and files | Fern Documentation

Fern Definition isn’t recommended for new customers and Fern isn’t accepting feature requests for this format. It remains supported for existing users.

The bytes type allows you to handle binary data in both requests and responses.

Sending bytes

If your API needs to send a stream of bytes (i.e. typical for assets like audio, images and other files) then you can use the bytes type in the Fern Definition to model this.

audio.yml

service:
  base-path: /audio
  endpoints:
    upload:
      display-name: Upload audio
      method: POST
      path: /upload
      content-type: application/octet-stream
      request:
        type: bytes
        docs: The bytes of the MP3 file that you would like to upload

Receiving bytes

When handling binary data in responses, use type: file instead of type: bytes.

On the other hand, if your API is returning a stream of bytes, then you can leverage the bytes type as a response.

textToSpeech.yml

service:
  base-path: /tts
  endpoints:
    upload:
      display-name: Upload audio
      method: POST
      path: ""
      request:
        name: TTSRequest
        body:
          properties:
            text:
              type: string
              docs: The text that you want converted to speech.
      response:
        type: file
        docs: The bytes of the audio file.