diff --git a/.travis.yml b/.travis.yml
index 7ae7cfec..5aa66c2e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,6 +11,28 @@ env:
  - LINKING="static"
 before_install:
  - eval "${MATRIX_EVAL}"
+ # Installing iwyu manually because clang and iwyu paths won't match on Ubuntu otherwise.
+ - if [ "$IWYU" = "iwyu" ]; then
+     CLANG_VERSION=`clang --version | grep version | cut -f3 -d' ' | cut -f1 -d'-'` ;
+     CLANG_PKG_VERSION=`echo $CLANG_VERSION | cut -f1,2 -d'.'`
+     CLANG_PREFIX_PATH="/usr/local/clang-${CLANG_VERSION}/lib/clang/${CLANG_VERSION}" ;
+     CLANG_BIN_PATH="/usr/local/clang-${CLANG_VERSION}/bin" ;
+     git clone https://github.com/include-what-you-use/include-what-you-use.git ;
+     cd include-what-you-use ;
+     echo "$CLANG_PKG_VERSION" | grep '\.[0-9]$' ;
+     if [ $? -eq 0 ]; then
+       git checkout clang_${CLANG_PKG_VERSION} ;
+     else
+       git checkout clang_${CLANG_PKG_VERSION}.0 ;
+     fi;
+     cd .. ;
+     mkdir build_iwyu ;
+     cd build_iwyu ;
+     cmake -G "Unix Makefiles" -DCMAKE_PREFIX_PATH=$CLANG_PREFIX_PATH -DCMAKE_C_COMPILER=$CLANG_BIN_PATH/clang -DCMAKE_CXX_COMPILER=$CLANG_BIN_PATH/clang++ ../include-what-you-use ;
+     make ;
+     sudo make install ;
+     cd .. ;
+   fi
  - export LDFLAGS="$LDFLAGS -L/usr/local/lib -L/usr/lib"
  - export PATH=$PATH:/usr/local/lib
  - export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib
@@ -37,7 +59,8 @@ install:
  - ./bootstrap
  - mkdir build
  - cd build
- - if [ "$LINKING" = "static" ]; then
+ - |
+   if [ "$LINKING" = "static" ]; then
      ../configure --enable-static --disable-fastopen;
    elif [ "$DEBUG" = "debug" ] && [ "$COVERAGE" = "coverage" ]; then
      ../configure --enable-debug --enable-coverage --disable-shared --disable-fastopen;
@@ -45,13 +68,23 @@ install:
      ../configure --enable-debug --disable-shared --disable-fastopen;
    elif [ "$VALGRIND" = "valgrind" ]; then
      ../configure --enable-debug --disable-fastopen --disable-valgrind-helgrind --disable-valgrind-drd --disable-valgrind-sgcheck;
+   elif [ "$IWYU" = "iwyu" ]; then
+     ../configure --disable-examples;
    else
      ../configure --disable-fastopen;
    fi
- - make
+ # Make or run iwyu. If running iwyu, check for the result code to be 2 (IWYU always returns an error code, if it is 2, no corrections are necessary).
+ - |
+   if [ "$IWYU" = "iwyu" ]; then
+     make -k CXX='/usr/local/bin/include-what-you-use -Xiwyu --mapping_file=${top_builddir}/../custom_iwyu.imp' CXXFLAGS="-isystem ${CLANG_PREFIX_PATH}/include -std=c++11 -DHTTPSERVER_COMPILATION -D_REENTRANT $CXXFLAGS" ;
+     if [ $? -ne 2 ]; then 
+       return 1;
+     fi
+   else
+     make;
+   fi
 script:
- - make check
- - cat test/test-suite.log
+ - if [ "$IWYU" != "iwyu" ]; then make check; cat test/test-suite.log; fi
  - if [ "$VALGRIND" = "valgrind" ]; then make check-valgrind; fi;
  - if [ "$VALGRIND" = "valgrind" ]; then cat test/test-suite-memcheck.log; fi;
  - if [ "$TRAVIS_OS_NAME" = "linux" ]; then cd ../src/; cppcheck --error-exitcode=1 .; cd ../build; fi
@@ -309,3 +342,17 @@ matrix:
             - clang-9
       env:
         - MATRIX_EVAL="CC=clang-9 && CXX=clang++-9"
+    - os: linux
+      compiler: clang
+      addons:
+        apt:
+          sources:
+            - llvm-toolchain-xenial-7
+            - ubuntu-toolchain-r-test
+          packages:
+            - iwyu
+            - cmake
+            - llvm-dev
+            - libclang-dev
+      env:
+        - MATRIX_EVAL="IWYU=iwyu"
diff --git a/appveyor.yml b/appveyor.yml
index 4fc56074..c86df7e5 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,13 +1,5 @@
 platform: x64
 
-branches:
-  except:
-    - /.*travis.*/
-skip_commits:
-  message: /travis/
-  files:
-    - .travis.yml
-
 environment:
   matrix:
     - compiler: msys2
diff --git a/custom_iwyu.imp b/custom_iwyu.imp
new file mode 100644
index 00000000..e814a310
--- /dev/null
+++ b/custom_iwyu.imp
@@ -0,0 +1,17 @@
+[
+  { include: ["\"microhttpd.h\"", "private", "<microhttpd.h>", "public"] },
+  { include: ["<ext/alloc_traits.h>", "private", "<memory>", "public"] },
+  
+  { symbol: ["std::exception",     "private", "<exception>", "public"]},
+  { symbol: ["std::shared_ptr",    "private", "<memory>",    "public"]},
+  { symbol: ["std::uint16_t",      "private", "<cstdint>",   "public"]},
+  { symbol: ["std::uint64_t",      "private", "<cstdint>",   "public"]},
+  { symbol: ["std::istringstream", "private", "<sstream>",   "public"]},
+  { symbol: ["std::stringstream",  "private", "<sstream>",   "public"]},
+  { symbol: ["std::ifstream",      "private", "<fstream>",   "public"]},
+
+  { symbol: ["uint16_t", "private", "<stdint.h>", "public"]},
+  { symbol: ["uint64_t", "private", "<stdint.h>", "public"]},
+
+  { symbol: ["MHD_Connection", "private", "<microhttpd.h>", "public"]},
+]
diff --git a/src/basic_auth_fail_response.cpp b/src/basic_auth_fail_response.cpp
index 500fceb6..49d9f5a9 100644
--- a/src/basic_auth_fail_response.cpp
+++ b/src/basic_auth_fail_response.cpp
@@ -19,6 +19,10 @@
 */
 
 #include "httpserver/basic_auth_fail_response.hpp"
+#include <microhttpd.h>
+
+struct MHD_Connection;
+struct MHD_Response;
 
 using namespace std;
 
diff --git a/src/deferred_response.cpp b/src/deferred_response.cpp
index 08033c80..f3d44527 100644
--- a/src/deferred_response.cpp
+++ b/src/deferred_response.cpp
@@ -19,6 +19,9 @@
 */
 
 #include "httpserver/deferred_response.hpp"
+#include <microhttpd.h>
+
+struct MHD_Response;
 
 using namespace std;
 
diff --git a/src/details/http_endpoint.cpp b/src/details/http_endpoint.cpp
index be76ddde..584fb507 100644
--- a/src/details/http_endpoint.cpp
+++ b/src/details/http_endpoint.cpp
@@ -18,12 +18,18 @@
      USA
 */
 
+#include <ctype.h>
+#include <map>
+#include <memory>
+#include <regex>
+#include <sstream>
 #include <stdexcept>
+#include <string>
+#include <utility>
+#include <vector>
 
 #include "httpserver/details/http_endpoint.hpp"
-
 #include "httpserver/http_utils.hpp"
-#include "httpserver/string_utilities.hpp"
 
 using namespace std;
 
diff --git a/src/digest_auth_fail_response.cpp b/src/digest_auth_fail_response.cpp
index d2fd5263..ca95526d 100644
--- a/src/digest_auth_fail_response.cpp
+++ b/src/digest_auth_fail_response.cpp
@@ -19,6 +19,10 @@
 */
 
 #include "httpserver/digest_auth_fail_response.hpp"
+#include <microhttpd.h>
+
+struct MHD_Connection;
+struct MHD_Response;
 
 using namespace std;
 
diff --git a/src/file_response.cpp b/src/file_response.cpp
index 1503e4bd..66d13a1c 100644
--- a/src/file_response.cpp
+++ b/src/file_response.cpp
@@ -19,8 +19,12 @@
 */
 
 #include "httpserver/file_response.hpp"
-
 #include <fcntl.h>
+#include <microhttpd.h>
+#include <stddef.h>
+#include <unistd.h>
+
+struct MHD_Response;
 
 using namespace std;
 
diff --git a/src/http_request.cpp b/src/http_request.cpp
index be342c7c..d7d8e2af 100644
--- a/src/http_request.cpp
+++ b/src/http_request.cpp
@@ -20,9 +20,9 @@
 */
 
 #include "httpserver/http_request.hpp"
-
+#include <stdio.h>
+#include <stdlib.h>
 #include <iostream>
-
 #include "httpserver/http_utils.hpp"
 #include "httpserver/string_utilities.hpp"
 
diff --git a/src/http_resource.cpp b/src/http_resource.cpp
index 0fc6402a..46bdb0de 100644
--- a/src/http_resource.cpp
+++ b/src/http_resource.cpp
@@ -19,15 +19,10 @@
 */
 
 #include "httpserver/http_resource.hpp"
-
-#include <stdlib.h>
-
-#include "httpserver/http_request.hpp"
-#include "httpserver/http_response.hpp"
-#include "httpserver/http_utils.hpp"
+#include <microhttpd.h>
 #include "httpserver/string_response.hpp"
-#include "httpserver/string_utilities.hpp"
-#include "httpserver/webserver.hpp"
+
+namespace httpserver { class http_response; }
 
 using namespace std;
 
diff --git a/src/http_response.cpp b/src/http_response.cpp
index c502f2ac..2d261e3d 100644
--- a/src/http_response.cpp
+++ b/src/http_response.cpp
@@ -19,16 +19,10 @@
 */
 
 #include "httpserver/http_response.hpp"
-
-#include <fcntl.h>
-#include <unistd.h>
-#include <cstdio>
-#include <functional>
+#include <microhttpd.h>
 #include <iostream>
-#include <sstream>
-
+#include <utility>
 #include "httpserver/http_utils.hpp"
-#include "httpserver/webserver.hpp"
 
 using namespace std;
 
diff --git a/src/http_utils.cpp b/src/http_utils.cpp
index c9d3aa66..caefabc5 100644
--- a/src/http_utils.cpp
+++ b/src/http_utils.cpp
@@ -24,9 +24,6 @@
 #include <winsock2.h>
 #include <ws2tcpip.h>
 #else // WIN32 check
-#if defined(__FreeBSD__)
-#include <netinet/in.h>
-#endif // FreeBSD
 #include <arpa/inet.h>
 #include <netdb.h>
 #include <netinet/in.h>
@@ -36,10 +33,10 @@
 
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
-#include <iomanip>
 #include <fstream>
-#include <iostream>
+#include <iomanip>
+#include <iterator>
+#include <memory>
 #include <sstream>
 #include <stdexcept>
 #include <utility>
diff --git a/src/httpserver/basic_auth_fail_response.hpp b/src/httpserver/basic_auth_fail_response.hpp
index c7e2d476..a28fa3d9 100644
--- a/src/httpserver/basic_auth_fail_response.hpp
+++ b/src/httpserver/basic_auth_fail_response.hpp
@@ -25,8 +25,13 @@
 #ifndef _BASIC_AUTH_FAIL_RESPONSE_HPP_
 #define _BASIC_AUTH_FAIL_RESPONSE_HPP_
 
+#include <string>
+#include "http_utils.hpp"
 #include "httpserver/string_response.hpp"
 
+struct MHD_Connection;
+struct MHD_Response;
+
 namespace httpserver
 {
 
diff --git a/src/httpserver/deferred_response.hpp b/src/httpserver/deferred_response.hpp
index 2193f960..9e4601e2 100644
--- a/src/httpserver/deferred_response.hpp
+++ b/src/httpserver/deferred_response.hpp
@@ -25,10 +25,16 @@
 #ifndef _DEFERRED_RESPONSE_HPP_
 #define _DEFERRED_RESPONSE_HPP_
 
+#include <stddef.h>
+#include <stdint.h>
+#include <sys/types.h>
 #include <memory>
-
+#include <string>
+#include "http_utils.hpp"
 #include "httpserver/string_response.hpp"
 
+struct MHD_Response;
+
 namespace httpserver
 {
 
diff --git a/src/httpserver/digest_auth_fail_response.hpp b/src/httpserver/digest_auth_fail_response.hpp
index 292f477b..50abcee2 100644
--- a/src/httpserver/digest_auth_fail_response.hpp
+++ b/src/httpserver/digest_auth_fail_response.hpp
@@ -25,8 +25,13 @@
 #ifndef _DIGEST_AUTH_FAIL_RESPONSE_HPP_
 #define _DIGEST_AUTH_FAIL_RESPONSE_HPP_
 
+#include <string>
+#include "http_utils.hpp"
 #include "httpserver/string_response.hpp"
 
+struct MHD_Connection;
+struct MHD_Response;
+
 namespace httpserver
 {
 
diff --git a/src/httpserver/file_response.hpp b/src/httpserver/file_response.hpp
index cb80c114..0c9386fb 100644
--- a/src/httpserver/file_response.hpp
+++ b/src/httpserver/file_response.hpp
@@ -25,8 +25,12 @@
 #ifndef _FILE_RESPONSE_HPP_
 #define _FILE_RESPONSE_HPP_
 
+#include <string>
+#include "http_utils.hpp"
 #include "httpserver/http_response.hpp"
 
+struct MHD_Response;
+
 namespace httpserver
 {
 
diff --git a/src/httpserver/http_request.hpp b/src/httpserver/http_request.hpp
index 62e52751..6aacbfe6 100644
--- a/src/httpserver/http_request.hpp
+++ b/src/httpserver/http_request.hpp
@@ -25,6 +25,10 @@
 #ifndef _HTTP_REQUEST_HPP_
 #define _HTTP_REQUEST_HPP_
 
+#include <microhttpd.h>
+
+#include <stddef.h>
+#include <algorithm>
 #include <iosfwd>
 #include <map>
 #include <string>
@@ -38,14 +42,6 @@ struct MHD_Connection;
 namespace httpserver
 {
 
-class webserver;
-
-namespace http
-{
-    class header_comparator;
-    class arg_comparator;
-};
-
 /**
  * Class representing an abstraction for an Http Request. It is used from classes using these apis to receive information through http protocol.
 **/
diff --git a/src/httpserver/http_resource.hpp b/src/httpserver/http_resource.hpp
index 7841b96b..04f67cb8 100644
--- a/src/httpserver/http_resource.hpp
+++ b/src/httpserver/http_resource.hpp
@@ -28,24 +28,18 @@
 #ifdef DEBUG
 #include <iostream>
 #endif
+
 #include <map>
 #include <memory>
 #include <string>
+#include <utility>
 
-#include "httpserver/http_response.hpp"
-
-namespace httpserver
-{
+namespace httpserver { class http_request; }
+namespace httpserver { class http_response; }
 
-class webserver;
-class http_request;
+namespace httpserver {
 
-namespace details
-{
-
-std::shared_ptr<http_response> empty_render(const http_request& r);
-
-};
+namespace details { std::shared_ptr<http_response> empty_render(const http_request& r); };
 
 /**
  * Class representing a callable http resource.
diff --git a/src/httpserver/http_response.hpp b/src/httpserver/http_response.hpp
index 33c1df42..1f3f0971 100644
--- a/src/httpserver/http_response.hpp
+++ b/src/httpserver/http_response.hpp
@@ -27,11 +27,7 @@
 
 #include <iosfwd>
 #include <map>
-#include <stdint.h>
 #include <string>
-#include <utility>
-#include <vector>
-
 #include "httpserver/http_utils.hpp"
 
 struct MHD_Connection;
diff --git a/src/httpserver/http_utils.hpp b/src/httpserver/http_utils.hpp
index a8121977..e2aa0339 100644
--- a/src/httpserver/http_utils.hpp
+++ b/src/httpserver/http_utils.hpp
@@ -43,9 +43,14 @@
 #endif
 
 #include <microhttpd.h>
+#include <stddef.h>
+
+#if !defined(__MINGW32__)
+#include <sys/socket.h>
+#endif
+
 #include <algorithm>
 #include <cctype>
-#include <exception>
 #include <iosfwd>
 #include <map>
 #include <string>
diff --git a/src/httpserver/string_response.hpp b/src/httpserver/string_response.hpp
index 1c2183d0..43e7580d 100644
--- a/src/httpserver/string_response.hpp
+++ b/src/httpserver/string_response.hpp
@@ -25,8 +25,13 @@
 #ifndef _STRING_RESPONSE_HPP_
 #define _STRING_RESPONSE_HPP_
 
+#include <string>
+#include <utility>
+#include "http_utils.hpp"
 #include "httpserver/http_response.hpp"
 
+struct MHD_Response;
+
 namespace httpserver
 {
 
diff --git a/src/httpserver/webserver.hpp b/src/httpserver/webserver.hpp
index c1ca06de..02d626c5 100644
--- a/src/httpserver/webserver.hpp
+++ b/src/httpserver/webserver.hpp
@@ -30,35 +30,32 @@
 #define NOT_METHOD_ERROR "Method not Acceptable"
 #define GENERIC_ERROR "Internal Error"
 
+#include <microhttpd.h>
 #include <pthread.h>
+#include <stdarg.h>
+#include <stdint.h>
 #include <stdlib.h>
-#include <cstring>
-#include <deque>
+
+#if !defined(__MINGW32__)
+#include <sys/socket.h>
+#endif
+
 #include <map>
 #include <memory>
 #include <set>
-#include <stdexcept>
 #include <string>
-#include <utility>
-#include <vector>
 
+#include "http_utils.hpp"
 #include "httpserver/create_webserver.hpp"
 #include "httpserver/details/http_endpoint.hpp"
-#include "httpserver/http_response.hpp"
 
-namespace httpserver {
+namespace httpserver { class http_resource; }
+namespace httpserver { class http_response; }
+namespace httpserver { namespace details { struct modded_request; } }
 
-class http_resource;
-class create_webserver;
+struct MHD_Connection;
 
-namespace http {
-struct ip_representation;
-struct httpserver_ska;
-};
-
-namespace details {
-    struct modded_request;
-}
+namespace httpserver {
 
 /**
  * Class representing the webserver. Main class of the apis.
diff --git a/src/string_response.cpp b/src/string_response.cpp
index 7720d61b..75a557f8 100644
--- a/src/string_response.cpp
+++ b/src/string_response.cpp
@@ -19,6 +19,10 @@
 */
 
 #include "httpserver/string_response.hpp"
+#include <microhttpd.h>
+#include <stddef.h>
+
+struct MHD_Response;
 
 using namespace std;
 
diff --git a/src/string_utilities.cpp b/src/string_utilities.cpp
index c557fe06..a3937f2e 100644
--- a/src/string_utilities.cpp
+++ b/src/string_utilities.cpp
@@ -22,9 +22,6 @@
 
 #include <algorithm>
 #include <cctype>
-#include <cstdlib>
-#include <cstring>
-#include <istream>
 #include <sstream>
 #include <string>
 #include <vector>
diff --git a/src/webserver.cpp b/src/webserver.cpp
index 6b7dd47f..38542f2a 100644
--- a/src/webserver.cpp
+++ b/src/webserver.cpp
@@ -31,26 +31,16 @@
 #if defined(__CYGWIN__)
 #include <sys/select.h>
 #endif
-#include <netinet/ip.h>
+#include <netinet/in.h>
 #include <netinet/tcp.h>
 #endif
 
 #include <errno.h>
-#include <fcntl.h>
-#include <inttypes.h>
 #include <microhttpd.h>
 #include <signal.h>
-#include <stdexcept>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <sys/stat.h>
-#include <sys/time.h>
-#include <sys/types.h>
-#include <unistd.h>
-#include <algorithm>
-#include <iostream>
-#include <strings.h>
 #include <cstring>
 #include <exception>
 #include <memory>
@@ -67,7 +57,8 @@
 #include "httpserver/http_response.hpp"
 #include "httpserver/http_utils.hpp"
 #include "httpserver/string_response.hpp"
-#include "httpserver/string_utilities.hpp"
+
+struct MHD_Connection;
 
 #define _REENTRANT 1