diff --git a/.gitignore b/.gitignore
index 29daf6a..b3f7949 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,8 +7,10 @@ cmake_install.cmake
 install_manifest.txt
 *.cmake
 #Additions to https://github.com/github/gitignore/blob/master/CMake.gitignore
+build
 Testing
 compile_commands.json
+.cache
 .usages_clang
 
 *.crt
diff --git a/CMakeLists.txt b/CMakeLists.txt
index fb8ca62..8c16916 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,15 +24,37 @@ target_link_libraries(simple-web-server INTERFACE Threads::Threads)
 
 if(USE_STANDALONE_ASIO)
     target_compile_definitions(simple-web-server INTERFACE ASIO_STANDALONE)
-    find_path(ASIO_PATH asio.hpp)
-    if(NOT ASIO_PATH)
-        message(FATAL_ERROR "Standalone Asio not found")
+    # There is no canonical way to use Asio from CMake.
+    # In particular, Asio does not support CMake natively.
+    # However, Conan and Vcpkg do provide CMake support on their own.
+    # Prefer the CMake target and fall back to finding asio.hpp.
+    if(NOT TARGET asio::asio)
+        find_package(asio)
+    endif()
+    if(TARGET asio::asio)
+        target_link_libraries(simple-web-server INTERFACE asio::asio)
     else()
+        find_path(ASIO_PATH asio.hpp)
+        if(NOT ASIO_PATH)
+            message(FATAL_ERROR "Standalone Asio not found")
+        endif()
         target_include_directories(simple-web-server SYSTEM INTERFACE ${ASIO_PATH})
     endif()
 else()
-    find_package(Boost 1.53.0 COMPONENTS system REQUIRED)
-    target_link_libraries(simple-web-server INTERFACE Boost::boost Boost::system)
+    # In Boost 1.89.0+, system is header-only, so we try to find it but make it optional
+    find_package(Boost 1.53.0 COMPONENTS system)
+    if(NOT Boost_FOUND)
+        # Fallback: try without system component for newer Boost versions where it's header-only
+        find_package(Boost 1.53.0 REQUIRED)
+    endif()
+
+    target_link_libraries(simple-web-server INTERFACE Boost::boost)
+
+    # Only link Boost::system if the target exists (for older Boost < 1.89)
+    if(TARGET Boost::system)
+        target_link_libraries(simple-web-server INTERFACE Boost::system)
+    endif()
+
     if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.9)
         target_compile_definitions(simple-web-server INTERFACE USE_BOOST_REGEX)
         find_package(Boost 1.53.0 COMPONENTS regex REQUIRED)
@@ -61,7 +83,7 @@ endif()
 # If Simple-Web-Server is not a sub-project:
 if(CMAKE_SOURCE_DIR STREQUAL "${CMAKE_CURRENT_SOURCE_DIR}")
     if(NOT MSVC)
-        add_compile_options(-Wall -Wextra)
+        add_compile_options(-Wall -Wextra -Wsign-conversion)
         if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
             add_compile_options(-Wthread-safety)
         endif()
diff --git a/asio_compatibility.hpp b/asio_compatibility.hpp
index aa43451..e93c0cf 100644
--- a/asio_compatibility.hpp
+++ b/asio_compatibility.hpp
@@ -27,12 +27,18 @@ namespace SimpleWeb {
 #endif
 
 namespace SimpleWeb {
-#if(defined(ASIO_STANDALONE) && ASIO_VERSION >= 101300) || BOOST_ASIO_VERSION >= 101300
+#if (defined(ASIO_STANDALONE) && ASIO_VERSION >= 103300) || BOOST_ASIO_VERSION >= 103300
+  using const_buffer = asio::const_buffer;
+#else
+  using const_buffer = asio::const_buffers_1;
+#endif
+
+#if (defined(ASIO_STANDALONE) && ASIO_VERSION >= 101300) || BOOST_ASIO_VERSION >= 101300
   using io_context = asio::io_context;
   using resolver_results = asio::ip::tcp::resolver::results_type;
   using async_connect_endpoint = asio::ip::tcp::endpoint;
 
-#if(defined(ASIO_STANDALONE) && ASIO_VERSION >= 101800) || BOOST_ASIO_VERSION >= 101800
+#if (defined(ASIO_STANDALONE) && ASIO_VERSION >= 101800) || BOOST_ASIO_VERSION >= 101800
   using strand = asio::strand<asio::any_io_executor>;
 #else
   using strand = asio::strand<asio::executor>;
diff --git a/client_http.hpp b/client_http.hpp
index e12fcd2..44f8ca1 100644
--- a/client_http.hpp
+++ b/client_http.hpp
@@ -17,7 +17,7 @@ namespace SimpleWeb {
 
   public:
     /// Match condition for asio::read_until to match both standard and non-standard HTTP header endings.
-    std::pair<asio::buffers_iterator<asio::const_buffers_1>, bool> operator()(asio::buffers_iterator<asio::const_buffers_1> begin, asio::buffers_iterator<asio::const_buffers_1> end) {
+    std::pair<asio::buffers_iterator<const_buffer>, bool> operator()(asio::buffers_iterator<const_buffer> begin, asio::buffers_iterator<const_buffer> end) {
       auto it = begin;
       for(; it != end; ++it) {
         if(*it == '\n') {
@@ -72,11 +72,11 @@ namespace SimpleWeb {
       friend class ClientBase<socket_type>;
 
     public:
-      std::size_t size() noexcept {
+      std::size_t size() const noexcept {
         return streambuf.size();
       }
       /// Convenience function to return content as a string.
-      std::string string() noexcept {
+      std::string string() const noexcept {
         return std::string(asio::buffers_begin(streambuf.data()), asio::buffers_end(streambuf.data()));
       }
 
diff --git a/client_https.hpp b/client_https.hpp
index 86c042c..09d37ab 100644
--- a/client_https.hpp
+++ b/client_https.hpp
@@ -27,7 +27,7 @@ namespace SimpleWeb {
     Client(const std::string &server_port_path, bool verify_certificate = true, const std::string &certification_file = std::string(),
            const std::string &private_key_file = std::string(), const std::string &verify_file = std::string())
         : ClientBase<HTTPS>::ClientBase(server_port_path, 443),
-#if(defined(ASIO_STANDALONE) && ASIO_VERSION >= 101300) || BOOST_ASIO_VERSION >= 101300
+#if (defined(ASIO_STANDALONE) && ASIO_VERSION >= 101300) || BOOST_ASIO_VERSION >= 101300
           context(asio::ssl::context::tls_client) {
       // Disabling TLS 1.0 and 1.1 (see RFC 8996)
       context.set_options(asio::ssl::context::no_tlsv1);
@@ -41,7 +41,11 @@ namespace SimpleWeb {
       }
 
       if(verify_certificate)
+#if (defined(ASIO_STANDALONE) && ASIO_VERSION >= 103300) || BOOST_ASIO_VERSION >= 103300
+        context.set_verify_callback(asio::ssl::host_name_verification(host));
+#else
         context.set_verify_callback(asio::ssl::rfc2818_verification(host));
+#endif
 
       if(verify_file.size() > 0)
         context.load_verify_file(verify_file);
diff --git a/crypto.hpp b/crypto.hpp
index 3629598..be9bfb9 100644
--- a/crypto.hpp
+++ b/crypto.hpp
@@ -70,7 +70,7 @@ namespace SimpleWeb {
         b64 = BIO_new(BIO_f_base64());
         BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL);
 // TODO: Remove in 2022 or later
-#if(defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER < 0x1000214fL) || (defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x2080000fL)
+#if (defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER < 0x1000214fL) || (defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x2080000fL)
         bio = BIO_new_mem_buf(const_cast<char *>(&base64[0]), static_cast<int>(base64.size()));
 #else
         bio = BIO_new_mem_buf(&base64[0], static_cast<int>(base64.size()));
diff --git a/server_http.hpp b/server_http.hpp
index 1db0368..50f7a86 100644
--- a/server_http.hpp
+++ b/server_http.hpp
@@ -135,7 +135,7 @@ namespace SimpleWeb {
       }
 
     public:
-      std::size_t size() noexcept {
+      std::size_t size() const noexcept {
         return streambuf->size();
       }
 
@@ -209,11 +209,11 @@ namespace SimpleWeb {
       friend class ServerBase<socket_type>;
 
     public:
-      std::size_t size() noexcept {
+      std::size_t size() const noexcept {
         return streambuf.size();
       }
       /// Convenience function to return content as std::string.
-      std::string string() noexcept {
+      std::string string() const noexcept {
         return std::string(asio::buffers_begin(streambuf.data()), asio::buffers_end(streambuf.data()));
       }
 
@@ -227,11 +227,16 @@ namespace SimpleWeb {
       friend class Server<socket_type>;
       friend class Session;
 
-      asio::streambuf streambuf;
+      std::unique_ptr<asio::streambuf> streambuf;
+      asio::streambuf content_streambuf;
       std::weak_ptr<Connection> connection;
       std::string optimization = std::to_string(0); // TODO: figure out what goes wrong in gcc optimization without this line
 
-      Request(std::size_t max_request_streambuf_size, const std::shared_ptr<Connection> &connection_) noexcept : streambuf(max_request_streambuf_size), connection(connection_), content(streambuf) {}
+      Request(std::size_t max_request_streambuf_size, const std::shared_ptr<Connection> &connection_) noexcept
+          : streambuf(new asio::streambuf(max_request_streambuf_size)), content_streambuf(max_request_streambuf_size), connection(connection_), content(content_streambuf) {}
+      Request(std::size_t max_request_streambuf_size, const std::shared_ptr<Connection> &connection_, std::unique_ptr<asio::streambuf> &&previous_streambuf) noexcept
+          : streambuf(std::move(previous_streambuf)), content_streambuf(max_request_streambuf_size), connection(connection_), content(content_streambuf) {
+      }
 
     public:
       std::string method, path, query_string, http_version;
@@ -292,6 +297,10 @@ namespace SimpleWeb {
       CaseInsensitiveMultimap parse_query_string() const noexcept {
         return SimpleWeb::QueryString::parse(query_string);
       }
+
+      std::shared_ptr<Connection> connection_shared() const noexcept {
+        return connection.lock();
+      }
     };
 
   protected:
@@ -347,7 +356,10 @@ namespace SimpleWeb {
 
     class Session {
     public:
-      Session(std::size_t max_request_streambuf_size, std::shared_ptr<Connection> connection_) noexcept : connection(std::move(connection_)), request(new Request(max_request_streambuf_size, connection)) {}
+      Session(std::size_t max_request_streambuf_size, std::shared_ptr<Connection> connection_) noexcept
+          : connection(std::move(connection_)), request(new Request(max_request_streambuf_size, connection)) {}
+      Session(std::size_t max_request_streambuf_size, std::shared_ptr<Connection> connection_, std::unique_ptr<asio::streambuf> &&previous_streambuf) noexcept
+          : connection(std::move(connection_)), request(new Request(max_request_streambuf_size, connection, std::move(previous_streambuf))) {}
 
       std::shared_ptr<Connection> connection;
       std::shared_ptr<Request> request;
@@ -558,7 +570,7 @@ namespace SimpleWeb {
 
     void read(const std::shared_ptr<Session> &session) {
       session->connection->set_timeout(config.timeout_request);
-      asio::async_read_until(*session->connection->socket, session->request->streambuf, "\r\n\r\n", [this, session](const error_code &ec, std::size_t bytes_transferred) {
+      asio::async_read_until(*session->connection->socket, *session->request->streambuf, "\r\n\r\n", [this, session](const error_code &ec, std::size_t bytes_transferred) {
         auto lock = session->connection->handler_runner->continue_lock();
         if(!lock)
           return;
@@ -566,13 +578,14 @@ namespace SimpleWeb {
 
         if(!ec) {
           session->connection->set_timeout(this->config.timeout_content);
-          // request->streambuf.size() is not necessarily the same as bytes_transferred, from Boost-docs:
+          // request->streambuf->size() is not necessarily the same as bytes_transferred, from Boost-docs:
           // "After a successful async_read_until operation, the streambuf may contain additional data beyond the delimiter"
           // The chosen solution is to extract lines from the stream directly when parsing the header. What is left of the
           // streambuf (maybe some bytes of the content) is appended to in the async_read-function below (for retrieving content).
-          std::size_t num_additional_bytes = session->request->streambuf.size() - bytes_transferred;
+          std::size_t num_additional_bytes = session->request->streambuf->size() - bytes_transferred;
 
-          if(!RequestMessage::parse(session->request->content, session->request->method, session->request->path,
+          std::istream istream(session->request->streambuf.get());
+          if(!RequestMessage::parse(istream, session->request->method, session->request->path,
                                     session->request->query_string, session->request->http_version, session->request->header)) {
             if(this->on_error)
               this->on_error(session->request, make_error_code::make_error_code(errc::protocol_error));
@@ -591,15 +604,24 @@ namespace SimpleWeb {
                 this->on_error(session->request, make_error_code::make_error_code(errc::protocol_error));
               return;
             }
-            if(content_length > session->request->streambuf.max_size()) {
+            if(content_length > session->request->streambuf->max_size()) {
               auto response = std::shared_ptr<Response>(new Response(session, this->config.timeout_content));
               response->write(StatusCode::client_error_payload_too_large);
               if(this->on_error)
                 this->on_error(session->request, make_error_code::make_error_code(errc::message_size));
               return;
             }
+
+            if(num_additional_bytes > 0) {
+              auto content_bytes = std::min<std::size_t>(content_length, (unsigned long long)num_additional_bytes);
+              auto &source = *session->request->streambuf;
+              auto &target = session->request->content_streambuf;
+              target.commit(asio::buffer_copy(target.prepare(content_bytes), source.data(), content_bytes));
+              source.consume(content_bytes);
+            }
+
             if(content_length > num_additional_bytes) {
-              asio::async_read(*session->connection->socket, session->request->streambuf, asio::transfer_exactly(content_length - num_additional_bytes), [this, session](const error_code &ec, std::size_t /*bytes_transferred*/) {
+              asio::async_read(*session->connection->socket, session->request->content_streambuf, asio::transfer_exactly(content_length - num_additional_bytes), [this, session](const error_code &ec, std::size_t /*bytes_transferred*/) {
                 auto lock = session->connection->handler_runner->continue_lock();
                 if(!lock)
                   return;
@@ -610,15 +632,16 @@ namespace SimpleWeb {
                   this->on_error(session->request, ec);
               });
             }
-            else
+            else {
               this->find_resource(session);
+            }
           }
           else if((header_it = session->request->header.find("Transfer-Encoding")) != session->request->header.end() && header_it->second == "chunked") {
             // Expect hex number to not exceed 16 bytes (64-bit number), but take into account previous additional read bytes
-            auto chunk_size_streambuf = std::make_shared<asio::streambuf>(std::max<std::size_t>(16 + 2, session->request->streambuf.size()));
+            auto chunk_size_streambuf = std::make_shared<asio::streambuf>(std::max<std::size_t>(16 + 2, session->request->streambuf->size()));
 
             // Move leftover bytes
-            auto &source = session->request->streambuf;
+            auto &source = *session->request->streambuf;
             auto &target = *chunk_size_streambuf;
             target.commit(asio::buffer_copy(target.prepare(source.size()), source.data()));
             source.consume(source.size());
@@ -654,12 +677,7 @@ namespace SimpleWeb {
             return;
           }
 
-          if(chunk_size == 0) {
-            this->find_resource(session);
-            return;
-          }
-
-          if(chunk_size + session->request->streambuf.size() > session->request->streambuf.max_size()) {
+          if(chunk_size + session->request->content_streambuf.size() > session->request->content_streambuf.max_size()) {
             auto response = std::shared_ptr<Response>(new Response(session, this->config.timeout_content));
             response->write(StatusCode::client_error_payload_too_large);
             if(this->on_error)
@@ -667,19 +685,34 @@ namespace SimpleWeb {
             return;
           }
 
+          auto read_next = [this, chunk_size](const std::shared_ptr<Session> &session, const std::shared_ptr<asio::streambuf> &chunk_size_streambuf) {
+            if(chunk_size == 0) {
+              if(chunk_size_streambuf->size() > 0) {
+                // Remaining bytes are the beginning of the next request
+                auto &source = *chunk_size_streambuf;
+                auto &target = *session->request->streambuf;
+                target.commit(asio::buffer_copy(target.prepare(chunk_size_streambuf->size()), source.data(), chunk_size_streambuf->size()));
+                source.consume(chunk_size_streambuf->size());
+              }
+              this->find_resource(session);
+            }
+            else
+              this->read_chunked_transfer_encoded(session, chunk_size_streambuf);
+          };
+
           auto num_additional_bytes = chunk_size_streambuf->size() - bytes_transferred;
 
           auto bytes_to_move = std::min<std::size_t>(chunk_size, num_additional_bytes);
           if(bytes_to_move > 0) {
             // Move leftover bytes
             auto &source = *chunk_size_streambuf;
-            auto &target = session->request->streambuf;
+            auto &target = session->request->content_streambuf;
             target.commit(asio::buffer_copy(target.prepare(bytes_to_move), source.data(), bytes_to_move));
             source.consume(bytes_to_move);
           }
 
           if(chunk_size > num_additional_bytes) {
-            asio::async_read(*session->connection->socket, session->request->streambuf, asio::transfer_exactly(chunk_size - num_additional_bytes), [this, session, chunk_size_streambuf](const error_code &ec, size_t /*bytes_transferred*/) {
+            asio::async_read(*session->connection->socket, session->request->content_streambuf, asio::transfer_exactly(chunk_size - num_additional_bytes), [this, session, chunk_size_streambuf, read_next](const error_code &ec, size_t /*bytes_transferred*/) {
               auto lock = session->connection->handler_runner->continue_lock();
               if(!lock)
                 return;
@@ -687,12 +720,12 @@ namespace SimpleWeb {
               if(!ec) {
                 // Remove "\r\n"
                 auto null_buffer = std::make_shared<asio::streambuf>(2);
-                asio::async_read(*session->connection->socket, *null_buffer, asio::transfer_exactly(2), [this, session, chunk_size_streambuf, null_buffer](const error_code &ec, size_t /*bytes_transferred*/) {
+                asio::async_read(*session->connection->socket, *null_buffer, asio::transfer_exactly(2), [this, session, chunk_size_streambuf, null_buffer, read_next](const error_code &ec, size_t /*bytes_transferred*/) {
                   auto lock = session->connection->handler_runner->continue_lock();
                   if(!lock)
                     return;
                   if(!ec)
-                    read_chunked_transfer_encoded(session, chunk_size_streambuf);
+                    read_next(session, chunk_size_streambuf);
                   else
                     this->on_error(session->request, ec);
                 });
@@ -706,12 +739,12 @@ namespace SimpleWeb {
             if(2 + chunk_size - num_additional_bytes == 1)
               istream.get();
             auto null_buffer = std::make_shared<asio::streambuf>(2);
-            asio::async_read(*session->connection->socket, *null_buffer, asio::transfer_exactly(2 + chunk_size - num_additional_bytes), [this, session, chunk_size_streambuf, null_buffer](const error_code &ec, size_t /*bytes_transferred*/) {
+            asio::async_read(*session->connection->socket, *null_buffer, asio::transfer_exactly(2 + chunk_size - num_additional_bytes), [this, session, chunk_size_streambuf, null_buffer, read_next](const error_code &ec, size_t /*bytes_transferred*/) {
               auto lock = session->connection->handler_runner->continue_lock();
               if(!lock)
                 return;
               if(!ec)
-                read_chunked_transfer_encoded(session, chunk_size_streambuf);
+                read_next(session, chunk_size_streambuf);
               else
                 this->on_error(session->request, ec);
             });
@@ -721,7 +754,7 @@ namespace SimpleWeb {
             istream.get();
             istream.get();
 
-            read_chunked_transfer_encoded(session, chunk_size_streambuf);
+            read_next(session, chunk_size_streambuf);
           }
         }
         else if(this->on_error)
@@ -778,13 +811,13 @@ namespace SimpleWeb {
               if(case_insensitive_equal(it->second, "close"))
                 return;
               else if(case_insensitive_equal(it->second, "keep-alive")) {
-                auto new_session = std::make_shared<Session>(this->config.max_request_streambuf_size, response->session->connection);
+                auto new_session = std::make_shared<Session>(this->config.max_request_streambuf_size, response->session->connection, std::move(response->session->request->streambuf));
                 this->read(new_session);
                 return;
               }
             }
             if(response->session->request->http_version >= "1.1") {
-              auto new_session = std::make_shared<Session>(this->config.max_request_streambuf_size, response->session->connection);
+              auto new_session = std::make_shared<Session>(this->config.max_request_streambuf_size, response->session->connection, std::move(response->session->request->streambuf));
               this->read(new_session);
               return;
             }
diff --git a/server_https.hpp b/server_https.hpp
index 9b77fdc..7a02b68 100644
--- a/server_https.hpp
+++ b/server_https.hpp
@@ -29,7 +29,7 @@ namespace SimpleWeb {
      */
     Server(const std::string &certification_file, const std::string &private_key_file, const std::string &verify_file = std::string())
         : ServerBase<HTTPS>::ServerBase(443),
-#if(defined(ASIO_STANDALONE) && ASIO_VERSION >= 101300) || BOOST_ASIO_VERSION >= 101300
+#if (defined(ASIO_STANDALONE) && ASIO_VERSION >= 101300) || BOOST_ASIO_VERSION >= 101300
           context(asio::ssl::context::tls_server) {
       // Disabling TLS 1.0 and 1.1 (see RFC 8996)
       context.set_options(asio::ssl::context::no_tlsv1);