Please see https://api.dartlang.org/stable/1.23.0/dart-io/CompressionOptions/DEFAULT-constant.html

Compression will be enabled with the following options: clientNoContextTakeover: false serverNoContextTakeover: false clientMaxWindowBits: 15 serverMaxWindowBits: 15

In fact clientMaxWindowBits and serverMaxWindowBits have null values.

  print(CompressionOptions.DEFAULT.clientMaxWindowBits); // null
  print(CompressionOptions.DEFAULT.serverMaxWindowBits); // null