var
      MemoryStream1: TMemoryStream;
      IdHTTP1: TIdHTTP;
      Bytes1: TBytes;
      s1: string;
    begin
      IdHTTP1 := TIdHTTP.Create(nil);
      MemoryStream1 := TMemoryStream.Create;
      IdHTTP1.Get('https://restcountries.eu/rest/v2/all', MemoryStream1);
      MemoryStream1.Position := 0;
      MemoryStream1.SaveToFile('C:TempMemoryStream1.txt');
      MemoryStream1.Position := 0;
      SetLength(Bytes1, MemoryStream1.Size);
      MemoryStream1.Read(Bytes1[0], MemoryStream1.Size);
      s1 := TEncoding.UTF8.GetString(Bytes1);