diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index 59494f7..f4b9dd7 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -62,5 +62,8 @@ target_link_libraries(file_upload_server ${EXAMPLE_LIBS})
 add_executable(file_server file_server.cc)
 target_link_libraries(file_server ${EXAMPLE_LIBS})
 
+add_executable(file_downloader file_downloader.cc)
+target_link_libraries(file_downloader ${EXAMPLE_LIBS})
+
 add_executable(server_states server_states.cc)
 target_link_libraries(server_states ${EXAMPLE_LIBS})
diff --git a/examples/file_downloader.cc b/examples/file_downloader.cc
new file mode 100644
index 0000000..c42599d
--- /dev/null
+++ b/examples/file_downloader.cc
@@ -0,0 +1,44 @@
+// Download files.
+// This example demonstrates the usage of streamed response.
+
+#include <iostream>
+
+#include "webcc/client_session.h"
+#include "webcc/logger.h"
+
+void Help(const char* argv0) {
+  std::cout << "Usage: file_downloader <url> <path>" << std::endl;
+  std::cout << "E.g.," << std::endl;
+  std::cout << "    file_downloader http://httpbin.org/image/jpeg D:/test.jpg"
+            << std::endl;
+  std::cout << "    file_downloader https://www.google.com/favicon.ico"
+            << " D:/test.ico" << std::endl;
+}
+
+int main(int argc, char* argv[]) {
+  if (argc != 3) {
+    Help(argv[0]);
+    return 1;
+  }
+
+  std::string url = argv[1];
+  std::string path = argv[2];
+
+  WEBCC_LOG_INIT("", webcc::LOG_CONSOLE);
+
+  webcc::ClientSession session;
+
+  try {
+    auto r = session.Request(webcc::RequestBuilder{}.Get(url)(),
+                             true);  // Stream the response data to file.
+
+    auto file_body = r->file_body();
+
+    file_body->Move(path);
+
+  } catch (const std::exception& e) {
+    std::cerr << e.what() << std::endl;
+  }
+
+  return 0;
+}
diff --git a/unittest/request_parser_unittest.cc b/unittest/request_parser_unittest.cc
index f8e640c..ae3f9e0 100644
--- a/unittest/request_parser_unittest.cc
+++ b/unittest/request_parser_unittest.cc
@@ -8,7 +8,8 @@
 // HTTP GET request parser test fixture.
 class GetRequestParserTest : public testing::Test {
 protected:
-  GetRequestParserTest() : parser_(&request_) {
+  GetRequestParserTest() {
+    parser_.Init(&request_);
   }
 
   void SetUp() override {
@@ -81,7 +82,8 @@ TEST_F(GetRequestParserTest, ParseLineWise) {
 // HTTP POST request parser test fixture.
 class PostRequestParserTest : public testing::Test {
 protected:
-  PostRequestParserTest() : parser_(&request_) {
+  PostRequestParserTest() {
+    parser_.Init(&request_);
   }
 
   void SetUp() override {
@@ -146,7 +148,8 @@ TEST_F(PostRequestParserTest, ParseByteWise) {
 
 class MultipartRequestParserTest : public testing::Test {
 protected:
-  MultipartRequestParserTest() : parser_(&request_) {
+  MultipartRequestParserTest() {
+    parser_.Init(&request_);
   }
 
   void SetUp() override {
diff --git a/webcc/body.cc b/webcc/body.cc
index a473129..b8170f6 100644
--- a/webcc/body.cc
+++ b/webcc/body.cc
@@ -2,6 +2,7 @@
 
 #include "boost/algorithm/string.hpp"
 #include "boost/core/ignore_unused.hpp"
+#include "boost/filesystem/operations.hpp"
 
 #include "webcc/logger.h"
 #include "webcc/utility.h"
@@ -161,24 +162,40 @@ void FormBody::Free(std::size_t index) {
 // -----------------------------------------------------------------------------
 
 FileBody::FileBody(const Path& path, std::size_t chunk_size)
-    : path_(path), chunk_size_(chunk_size) {
+    : path_(path), chunk_size_(chunk_size), auto_delete_(false), size_(0) {
   size_ = utility::TellSize(path_);
   if (size_ == kInvalidLength) {
     throw Error{ Error::kFileError, "Cannot read the file" };
   }
 }
 
+FileBody::FileBody(const Path& path, bool auto_delete)
+    : path_(path), chunk_size_(0), auto_delete_(auto_delete), size_(0) {
+  // Don't need to tell file size.
+}
+
+FileBody::~FileBody() {
+  if (auto_delete_ && !path_.empty()) {
+    boost::system::error_code ec;
+    bfs::remove(path_, ec);
+    if (ec) {
+      LOG_ERRO("Failed to remove file (%s).", ec.message().c_str());
+    }
+  }
+}
+
 void FileBody::InitPayload() {
   assert(chunk_size_ > 0);
+
   chunk_.resize(chunk_size_);
 
-  if (stream_.is_open()) {
-    stream_.close();
+  if (ifstream_.is_open()) {
+    ifstream_.close();
   }
 
-  stream_.open(path_, std::ios::binary);
+  ifstream_.open(path_, std::ios::binary);
 
-  if (stream_.fail()) {
+  if (ifstream_.fail()) {
     throw Error{ Error::kFileError, "Cannot read the file" };
   }
 }
@@ -186,9 +203,9 @@ void FileBody::InitPayload() {
 Payload FileBody::NextPayload(bool free_previous) {
   boost::ignore_unused(free_previous);
 
-  if (stream_.read(&chunk_[0], chunk_.size()).gcount() > 0) {
+  if (ifstream_.read(&chunk_[0], chunk_.size()).gcount() > 0) {
     return {
-      boost::asio::buffer(chunk_.data(), (std::size_t)stream_.gcount())
+      boost::asio::buffer(chunk_.data(), (std::size_t)ifstream_.gcount())
     };
   }
   return {};
@@ -198,4 +215,27 @@ void FileBody::Dump(std::ostream& os, const std::string& prefix) const {
   os << prefix << "<file: " << path_.string() << ">" << std::endl;
 }
 
+bool FileBody::Move(const Path& new_path) {
+  if (path_ == new_path) {
+    return false;
+  }
+
+  if (ifstream_.is_open()) {
+    ifstream_.close();
+  }
+
+  boost::system::error_code ec;
+  bfs::rename(path_, new_path, ec);
+
+  if (ec) {
+    LOG_ERRO("Failed to rename file (%s).", ec.message().c_str());
+    return false;
+  }
+
+  // Reset original file path.
+  path_.clear();
+
+  return true;
+}
+
 }  // namespace webcc
diff --git a/webcc/body.h b/webcc/body.h
index 414abb0..479b466 100644
--- a/webcc/body.h
+++ b/webcc/body.h
@@ -147,8 +147,18 @@ private:
 // the memory.
 class FileBody : public Body {
 public:
+  // For message to be sent out.
   FileBody(const Path& path, std::size_t chunk_size);
 
+  // For message received.
+  // No |chunk_size| is needed since you don't iterate the payload of a
+  // received message.
+  // If |auto_delete| is true, the file will be deleted on destructor unless it
+  // is moved to another path (see Move()).
+  FileBody(const Path& path, bool auto_delete = false);
+
+  ~FileBody() override;
+
   std::size_t GetSize() const override {
     return size_;
   }
@@ -159,13 +169,26 @@ public:
 
   void Dump(std::ostream& os, const std::string& prefix) const override;
 
+  // Move (or rename) the file.
+  // Used to move the streamed file of the received message to a new place.
+  // Applicable to both client and server.
+  // After move, the original path will be reset to empty.
+  // If |new_path| and |path_| resolve to the same file, do nothing and just
+  // return false.
+  // If |new_path| resolves to an existing non-directory file, it is removed.
+  // If |new_path| resolves to an existing directory, it is removed if empty
+  // on ISO/IEC 9945 but is an error on Windows.
+  // See boost::filesystem::rename() for more details.
+  bool Move(const Path& new_path);
+
 private:
   Path path_;
   std::size_t chunk_size_;
+  bool auto_delete_;
 
   std::size_t size_;  // File size in bytes
 
-  boost::filesystem::ifstream stream_;
+  boost::filesystem::ifstream ifstream_;
   std::string chunk_;
 };
 
diff --git a/webcc/client.cc b/webcc/client.cc
index 77b281b..c389ee0 100644
--- a/webcc/client.cc
+++ b/webcc/client.cc
@@ -15,8 +15,20 @@ Client::Client()
       timer_canceled_(false) {
 }
 
-Error Client::Request(RequestPtr request, bool connect) {
-  Restart();
+Error Client::Request(RequestPtr request, bool connect, bool stream) {
+  io_context_.restart();
+
+  response_.reset(new Response{});
+  response_parser_.Init(response_.get(), stream);
+
+  closed_ = false;
+  timer_canceled_ = false;
+  error_ = Error{};
+
+  if (buffer_.size() != buffer_size_) {
+    LOG_VERB("Resize buffer: %u -> %u.", buffer_.size(), buffer_size_);
+    buffer_.resize(buffer_size_);
+  }
 
   // Response to HEAD could also have Content-Length.
   // Set this flag to skip the reading and parsing of the body.
@@ -64,22 +76,6 @@ void Client::Close() {
   socket_->Close();
 }
 
-void Client::Restart() {
-  io_context_.restart();
-
-  response_.reset(new Response{});
-  response_parser_.Init(response_.get());
-
-  closed_ = false;
-  timer_canceled_ = false;
-  error_ = Error{};
-
-  if (buffer_.size() != buffer_size_) {
-    LOG_VERB("Resize buffer: %u -> %u.", buffer_.size(), buffer_size_);
-    buffer_.resize(buffer_size_);
-  }
-}
-
 void Client::Connect(RequestPtr request) {
   if (request->url().scheme() == "https") {
 #if WEBCC_ENABLE_SSL
diff --git a/webcc/client.h b/webcc/client.h
index 74cdc4f..24b8a59 100644
--- a/webcc/client.h
+++ b/webcc/client.h
@@ -49,7 +49,7 @@ public:
   }
 
   // Connect to server, send request, wait until response is received.
-  Error Request(RequestPtr request, bool connect = true);
+  Error Request(RequestPtr request, bool connect = true, bool stream = false);
 
   // Close the socket.
   void Close();
@@ -59,8 +59,6 @@ public:
   bool closed() const { return closed_; }
 
 private:
-  void Restart();
-
   void Connect(RequestPtr request);
 
   void DoConnect(RequestPtr request, const std::string& default_port);
diff --git a/webcc/client_session.cc b/webcc/client_session.cc
index 09b704a..942b1e6 100644
--- a/webcc/client_session.cc
+++ b/webcc/client_session.cc
@@ -28,7 +28,7 @@ void ClientSession::AuthToken(const std::string& token) {
   return Auth("Token", token);
 }
 
-ResponsePtr ClientSession::Request(RequestPtr request) {
+ResponsePtr ClientSession::Request(RequestPtr request, bool stream) {
   assert(request);
 
   for (auto& h : headers_.data()) {
@@ -44,7 +44,7 @@ ResponsePtr ClientSession::Request(RequestPtr request) {
 
   request->Prepare();
 
-  return Send(request);
+  return Send(request, stream);
 }
 
 static void SetHeaders(const Strings& headers, RequestBuilder* builder) {
@@ -183,7 +183,7 @@ void ClientSession::InitHeaders() {
   headers_.Set(kConnection, "Keep-Alive");
 }
 
-ResponsePtr ClientSession::Send(RequestPtr request) {
+ResponsePtr ClientSession::Send(RequestPtr request, bool stream) {
   const ClientPool::Key key{ request->url() };
 
   // Reuse a pooled connection.
@@ -202,13 +202,13 @@ ResponsePtr ClientSession::Send(RequestPtr request) {
   client->set_buffer_size(buffer_size_);
   client->set_timeout(timeout_);
 
-  Error error = client->Request(request, !reuse);
+  Error error = client->Request(request, !reuse, stream);
 
   if (error) {
     if (reuse && error.code() == Error::kSocketWriteError) {
       LOG_WARN("Cannot send request with the reused connection. "
                "The server must have closed it, reconnect and try again.");
-      error = client->Request(request, true);
+      error = client->Request(request, true, stream);
     }
   }
 
diff --git a/webcc/client_session.h b/webcc/client_session.h
index 3ada4ef..48939f3 100644
--- a/webcc/client_session.h
+++ b/webcc/client_session.h
@@ -57,7 +57,11 @@ public:
 
   // Send a request.
   // Please use RequestBuilder to build the request.
-  ResponsePtr Request(RequestPtr request);
+  // If |stream| is true, the response data will be written into a temp file,
+  // the response body will be FileBody, and you can easily move the temp file
+  // to another path with FileBody::Move(). So |stream| is useful for
+  // downloading files (JPEG, etc.) or saving memory for huge data responses.
+  ResponsePtr Request(RequestPtr request, bool stream = false);
 
   // Shortcut for GET request.
   ResponsePtr Get(const std::string& url, const Strings& parameters = {},
@@ -85,7 +89,7 @@ public:
 private:
   void InitHeaders();
 
-  ResponsePtr Send(RequestPtr request);
+  ResponsePtr Send(RequestPtr request, bool stream);
 
 private:
   // Default media type for `Content-Type` header.
diff --git a/webcc/message.cc b/webcc/message.cc
index 6f474fe..c7d2709 100644
--- a/webcc/message.cc
+++ b/webcc/message.cc
@@ -31,14 +31,19 @@ void Message::SetBody(BodyPtr body, bool set_length) {
 
 const std::string& Message::data() const {
   static const std::string kEmptyData;
-
   auto string_body = std::dynamic_pointer_cast<StringBody>(body_);
-
-  if (string_body) {
-    return string_body->data();
+  if (!string_body) {
+    return kEmptyData;
   }
+  return string_body->data();
+}
 
-  return kEmptyData;
+std::shared_ptr<FileBody> Message::file_body() const {
+  auto file_body = std::dynamic_pointer_cast<FileBody>(body_);
+  if (!file_body) {
+    throw Error{ Error::kDataError, "Not a file body" };
+  }
+  return file_body;
 }
 
 bool Message::IsConnectionKeepAlive() const {
diff --git a/webcc/message.h b/webcc/message.h
index 1d02dc6..1a3e921 100644
--- a/webcc/message.h
+++ b/webcc/message.h
@@ -26,10 +26,14 @@ public:
     return body_;
   }
 
-  // Get the data from the string body.
-  // Exception Error(kDataError) will be thrown if the body is FormBody.
+  // Get the data from the (string) body.
+  // Empty string will be returned if the body is not a StringBody.
   const std::string& data() const;
 
+  // Get the body as a FileBody.
+  // Exception Error::kDataError will be thrown if the body is not a FileBody.
+  std::shared_ptr<FileBody> file_body() const;
+
   // ---------------------------------------------------------------------------
 
   void SetHeader(Header&& header) {
diff --git a/webcc/parser.cc b/webcc/parser.cc
index a4b7092..498de9a 100644
--- a/webcc/parser.cc
+++ b/webcc/parser.cc
@@ -1,6 +1,7 @@
 #include "webcc/parser.h"
 
 #include "boost/algorithm/string.hpp"
+#include "boost/filesystem/operations.hpp"
 
 #include "webcc/logger.h"
 #include "webcc/message.h"
@@ -10,29 +11,135 @@
 #include "webcc/gzip.h"
 #endif
 
+namespace bfs = boost::filesystem;
+
 namespace webcc {
 
 // -----------------------------------------------------------------------------
 
-namespace {
+ParseHandler::ParseHandler(Message* message, bool stream)
+    : message_(message), content_length_(kInvalidLength), stream_(stream),
+      streamed_size_(0) {
+  if (stream_) {
+    try {
+      temp_path_ = bfs::temp_directory_path() / bfs::unique_path();
+    } catch (const bfs::filesystem_error&) {
+      throw Error{ Error::kFileError, "Cannot generate temp file path" };
+    }
+
+    ofstream_.open(temp_path_, std::ios::binary);
+
+    if (ofstream_.fail()) {
+      throw Error{ Error::kFileError, "Cannot open the temp file" };
+    }
+  }
+}
+
+ParseHandler::~ParseHandler() {
+}
+
+void ParseHandler::OnStartLine(const std::string& start_line) {
+  message_->set_start_line(start_line);
+}
+
+void ParseHandler::OnContentLength(std::size_t content_length) {
+  content_length_ = content_length;
+
+  if (!stream_) {
+    // Reserve memory to avoid frequent reallocation when append.
+    // TODO: Don't know if it's really necessary.
+    try {
+      content_.reserve(content_length_);
+    } catch (const std::exception& e) {
+      LOG_ERRO("Failed to reserve content memory: %s.", e.what());
+    }
+  }
+}
+
+void ParseHandler::OnHeader(Header&& header) {
+  message_->SetHeader(std::move(header));
+}
+
+void ParseHandler::AddContent(const char* data, std::size_t count) {
+  if (stream_) {
+    ofstream_.write(data, count);
+    streamed_size_ += count;
+  } else {
+    content_.append(data, count);
+  }
+}
+
+void ParseHandler::AddContent(const std::string& data) {
+  if (stream_) {
+    ofstream_ << data;
+    streamed_size_ += data.size();
+  } else {
+    content_.append(data);
+  }
+}
 
-bool StringToSizeT(const std::string& str, int base, std::size_t* output) {
-  try {
-    *output = static_cast<std::size_t>(std::stoul(str, 0, base));
-  } catch (const std::exception&) {
+bool ParseHandler::IsFixedContentFull() const {
+  if (content_length_ == kInvalidLength) {
+    // Shouldn't be here.
+    // See Parser::ParseFixedContent().
     return false;
   }
+
+  if (stream_) {
+    return streamed_size_ >= content_length_;
+  } else {
+    return content_.length() >= content_length_;
+  }
+}
+
+bool ParseHandler::Finish() {
+  // Could be `kInvalidLength` (chunked).
+  // Could be `0` (empty body and `Content-Length : 0`).
+  message_->set_content_length(content_length_);
+
+  if (!stream_ && content_.empty()) {
+    // The call to message_->SetBody() is not necessary since message is
+    // always initialized with an empty body.
+    return true;
+  }
+
+  BodyPtr body;
+
+  if (stream_) {
+    ofstream_.close();
+
+    // Create a file body based on the streamed temp file.
+    body = std::make_shared<FileBody>(temp_path_, true);
+
+    // TODO: Compress
+
+  } else {
+    body = std::make_shared<StringBody>(std::move(content_), IsCompressed());
+
+#if WEBCC_ENABLE_GZIP
+    LOG_INFO("Decompress the HTTP content...");
+    if (!body->Decompress()) {
+      LOG_ERRO("Cannot decompress the HTTP content!");
+      return false;
+    }
+#else
+    LOG_WARN("Compressed HTTP content remains untouched.");
+#endif  // WEBCC_ENABLE_GZIP
+  }
+
+  message_->SetBody(body, false);
+
   return true;
 }
 
-}  // namespace
+bool ParseHandler::IsCompressed() const {
+  return message_->GetContentEncoding() != ContentEncoding::kUnknown;
+}
 
 // -----------------------------------------------------------------------------
 
-Parser::Parser(Message* message)
-    : message_(message),
-      content_length_(kInvalidLength),
-      start_line_parsed_(false),
+Parser::Parser()
+    : start_line_parsed_(false),
       content_length_parsed_(false),
       header_ended_(false),
       chunked_(false),
@@ -40,9 +147,9 @@ Parser::Parser(Message* message)
       finished_(false) {
 }
 
-void Parser::Init(Message* message) {
+void Parser::Init(Message* message, bool stream) {
   Reset();
-  message_ = message;
+  handler_.reset(new ParseHandler{ message, stream });
 }
 
 bool Parser::Parse(const char* data, std::size_t length) {
@@ -70,9 +177,7 @@ bool Parser::Parse(const char* data, std::size_t length) {
 
 void Parser::Reset() {
   pending_data_.clear();
-  content_.clear();
 
-  content_length_ = kInvalidLength;
   content_type_.Reset();
   start_line_parsed_ = false;
   content_length_parsed_ = false;
@@ -101,7 +206,8 @@ bool Parser::ParseHeaders() {
 
     if (!start_line_parsed_) {
       start_line_parsed_ = true;
-      message_->set_start_line(line);
+      handler_->OnStartLine(line);
+
       if (!ParseStartLine(line)) {
         return false;
       }
@@ -148,20 +254,15 @@ bool Parser::ParseHeaderLine(const std::string& line) {
   if (boost::iequals(header.first, headers::kContentLength)) {
     content_length_parsed_ = true;
 
-    if (!StringToSizeT(header.second, 10, &content_length_)) {
+    std::size_t content_length = kInvalidLength;
+    if (!utility::ToSize(header.second, 10, &content_length)) {
       LOG_ERRO("Invalid content length: %s.", header.second.c_str());
       return false;
     }
 
-    LOG_INFO("Content length: %u.", content_length_);
+    LOG_INFO("Content length: %u.", content_length);
+    handler_->OnContentLength(content_length);
 
-    // Reserve memory to avoid frequent reallocation when append.
-    try {
-      content_.reserve(content_length_);
-    } catch (const std::exception& e) {
-      LOG_ERRO("Failed to reserve content memory: %s.", e.what());
-      return false;
-    }
   } else if (boost::iequals(header.first, headers::kContentType)) {
     content_type_.Parse(header.second);
     if (!content_type_.Valid()) {
@@ -175,8 +276,7 @@ bool Parser::ParseHeaderLine(const std::string& line) {
     }
   }
 
-  message_->SetHeader(std::move(header));
-
+  handler_->OnHeader(std::move(header));
   return true;
 }
 
@@ -195,21 +295,21 @@ bool Parser::ParseFixedContent(const char* data, std::size_t length) {
     return true;
   }
 
-  if (content_length_ == kInvalidLength) {
+  if (handler_->content_length() == kInvalidLength) {
     // Invalid content length (syntax error).
     return false;
   }
 
   if (!pending_data_.empty()) {
     // This is the data left after the headers are parsed.
-    AppendContent(pending_data_);
+    handler_->AddContent(pending_data_);
     pending_data_.clear();
   }
 
   // Don't have to firstly put the data to the pending data.
-  AppendContent(data, length);
+  handler_->AddContent(data, length);
 
-  if (IsFixedContentFull()) {
+  if (handler_->IsFixedContentFull()) {
     // All content has been read.
     Finish();
   }
@@ -236,7 +336,7 @@ bool Parser::ParseChunkedContent(const char* data, std::size_t length) {
     }
 
     if (chunk_size_ + 2 <= pending_data_.size()) {  // +2 for CRLF
-      AppendContent(pending_data_.c_str(), chunk_size_);
+      handler_->AddContent(pending_data_.c_str(), chunk_size_);
 
       pending_data_.erase(0, chunk_size_ + 2);
 
@@ -247,7 +347,7 @@ bool Parser::ParseChunkedContent(const char* data, std::size_t length) {
       continue;
 
     } else if (chunk_size_ > pending_data_.size()) {
-      AppendContent(pending_data_);
+      handler_->AddContent(pending_data_);
 
       chunk_size_ -= pending_data_.size();
 
@@ -287,7 +387,7 @@ bool Parser::ParseChunkSize() {
     hex_str = line;
   }
 
-  if (!StringToSizeT(hex_str, 16, &chunk_size_)) {
+  if (!utility::ToSize(hex_str, 16, &chunk_size_)) {
     LOG_ERRO("Invalid chunk-size: %s.", hex_str.c_str());
     return false;
   }
@@ -297,46 +397,7 @@ bool Parser::ParseChunkSize() {
 
 bool Parser::Finish() {
   finished_ = true;
-
-  if (content_.empty()) {
-    return true;
-  }
-
-  // Could be kInvalidLength when chunked.
-  message_->set_content_length(content_length_);
-
-  bool compressed = IsContentCompressed();
-  auto body = std::make_shared<StringBody>(std::move(content_), compressed);
-
-#if WEBCC_ENABLE_GZIP
-  LOG_INFO("Decompress the HTTP content...");
-  if (!body->Decompress()) {
-    LOG_ERRO("Cannot decompress the HTTP content!");
-    return false;
-  }
-#else
-  LOG_WARN("Compressed HTTP content remains untouched.");
-#endif  // WEBCC_ENABLE_GZIP
-
-  message_->SetBody(body, false);
-  return true;
-}
-
-void Parser::AppendContent(const char* data, std::size_t count) {
-  content_.append(data, count);
-}
-
-void Parser::AppendContent(const std::string& data) {
-  content_.append(data);
-}
-
-bool Parser::IsFixedContentFull() const {
-  return content_length_ != kInvalidLength &&
-         content_length_ <= content_.length();
-}
-
-bool Parser::IsContentCompressed() const {
-  return message_->GetContentEncoding() != ContentEncoding::kUnknown;
+  return handler_->Finish();
 }
 
 }  // namespace webcc
diff --git a/webcc/parser.h b/webcc/parser.h
index f724a97..5b7f1eb 100644
--- a/webcc/parser.h
+++ b/webcc/parser.h
@@ -3,6 +3,8 @@
 
 #include <string>
 
+#include "boost/filesystem/fstream.hpp"
+
 #include "webcc/common.h"
 #include "webcc/globals.h"
 
@@ -10,26 +12,66 @@ namespace webcc {
 
 class Message;
 
+// -----------------------------------------------------------------------------
+
+class ParseHandler {
+public:
+  // If |stream| is true, the data will be streamed to a temp file, and the
+  // body of the message will be FileBody instead of StringBody.
+  ParseHandler(Message* message, bool stream = false);
+
+  ~ParseHandler();
+
+  std::size_t content_length() const {
+    return content_length_;
+  }
+
+  void OnStartLine(const std::string& start_line);
+
+  void OnContentLength(std::size_t content_length);
+
+  void OnHeader(Header&& header);
+
+  void AddContent(const char* data, std::size_t count);
+
+  void AddContent(const std::string& data);
+
+  bool IsFixedContentFull() const;
+
+  bool Finish();
+
+private:
+  bool IsCompressed() const;
+
+private:
+  Message* message_;
+
+  std::size_t content_length_;
+  std::string content_;
+
+  bool stream_;
+  std::size_t streamed_size_;
+  boost::filesystem::ofstream ofstream_;
+  Path temp_path_;
+};
+
+// -----------------------------------------------------------------------------
+
 // HTTP request and response parser.
 class Parser {
 public:
-  explicit Parser(Message* message);
-
+  Parser();
   virtual ~Parser() = default;
 
   Parser(const Parser&) = delete;
   Parser& operator=(const Parser&) = delete;
 
-  void Init(Message* message);
+  void Init(Message* message, bool stream = false);
 
   bool finished() const {
     return finished_;
   }
 
-  std::size_t content_length() const {
-    return content_length_;
-  }
-
   bool Parse(const char* data, std::size_t length);
 
 protected:
@@ -60,25 +102,14 @@ protected:
   // Return false if the compressed content cannot be decompressed.
   bool Finish();
 
-  void AppendContent(const char* data, std::size_t count);
-  void AppendContent(const std::string& data);
-
-  bool IsFixedContentFull() const;
-
-  // Check header Content-Encoding to see if the content is compressed.
-  bool IsContentCompressed() const;
-
 protected:
-  // The message parsed.
-  Message* message_;
+  std::unique_ptr<ParseHandler> handler_;
 
   // Data waiting to be parsed.
   std::string pending_data_;
 
   // Temporary data and helper flags for parsing.
-  std::size_t content_length_;
   ContentType content_type_;
-  std::string content_;
   bool start_line_parsed_;
   bool content_length_parsed_;
   bool header_ended_;
diff --git a/webcc/request_parser.cc b/webcc/request_parser.cc
index 9fe294a..f277b5f 100644
--- a/webcc/request_parser.cc
+++ b/webcc/request_parser.cc
@@ -10,8 +10,7 @@
 
 namespace webcc {
 
-RequestParser::RequestParser(Request* request)
-    : Parser(request), request_(request) {
+RequestParser::RequestParser() : request_(nullptr) {
 }
 
 void RequestParser::Init(Request* request) {
@@ -51,7 +50,7 @@ bool RequestParser::ParseMultipartContent(const char* data,
                                           std::size_t length) {
   pending_data_.append(data, length);
 
-  if (!content_length_parsed_ || content_length_ == kInvalidLength) {
+  if (!content_length_parsed_ || handler_->content_length() == kInvalidLength) {
     // Invalid content length (syntax error).
     return false;
   }
diff --git a/webcc/request_parser.h b/webcc/request_parser.h
index d18f650..bc808d8 100644
--- a/webcc/request_parser.h
+++ b/webcc/request_parser.h
@@ -11,7 +11,7 @@ class Request;
 
 class RequestParser : public Parser {
 public:
-  explicit RequestParser(Request* request = nullptr);
+  RequestParser();
 
   ~RequestParser() override = default;
 
diff --git a/webcc/response_parser.cc b/webcc/response_parser.cc
index d48f9fd..47f2c61 100644
--- a/webcc/response_parser.cc
+++ b/webcc/response_parser.cc
@@ -38,12 +38,11 @@ void SplitStartLine(const std::string& line, std::vector<std::string>* parts) {
 
 // -----------------------------------------------------------------------------
 
-ResponseParser::ResponseParser(Response* response)
-    : Parser(response), response_(response) {
+ResponseParser::ResponseParser() : response_(nullptr) {
 }
 
-void ResponseParser::Init(Response* response) {
-  Parser::Init(response);
+void ResponseParser::Init(Response* response, bool stream) {
+  Parser::Init(response, stream);
   response_ = response;
 }
 
diff --git a/webcc/response_parser.h b/webcc/response_parser.h
index 5498a06..134b566 100644
--- a/webcc/response_parser.h
+++ b/webcc/response_parser.h
@@ -11,11 +11,11 @@ class Response;
 
 class ResponseParser : public Parser {
 public:
-  explicit ResponseParser(Response* response = nullptr);
+  ResponseParser();
 
   ~ResponseParser() override = default;
 
-  void Init(Response* response);
+  void Init(Response* response, bool stream = false);
 
   void set_ignroe_body(bool ignroe_body) {
     ignroe_body_ = ignroe_body;
diff --git a/webcc/utility.cc b/webcc/utility.cc
index ec25386..300173b 100644
--- a/webcc/utility.cc
+++ b/webcc/utility.cc
@@ -51,6 +51,15 @@ bool SplitKV(const std::string& str, char delimiter,
   return true;
 }
 
+bool ToSize(const std::string& str, int base, std::size_t* size) {
+  try {
+    *size = static_cast<std::size_t>(std::stoul(str, 0, base));
+  } catch (const std::exception&) {
+    return false;
+  }
+  return true;
+}
+
 std::size_t TellSize(const Path& path) {
   // Flag "ate": seek to the end of stream immediately after open.
   bfs::ifstream stream{ path, std::ios::binary | std::ios::ate };
diff --git a/webcc/utility.h b/webcc/utility.h
index 9c76cc2..9ba70e9 100644
--- a/webcc/utility.h
+++ b/webcc/utility.h
@@ -24,6 +24,9 @@ std::string GetTimestamp();
 bool SplitKV(const std::string& str, char delimiter,
              std::string* key, std::string* value);
 
+// Convert string to size_t.
+bool ToSize(const std::string& str, int base, std::size_t* size);
+
 // Tell the size in bytes of the given file.
 // Return kInvalidLength (-1) on failure.
 std::size_t TellSize(const Path& path);