diff --git a/CMakeLists.txt b/CMakeLists.txt
index 00dfb580..8ad61563 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -279,7 +279,6 @@ set(LIBLOOT_SRC_API_H_FILES
     "${CMAKE_SOURCE_DIR}/src/api/sorting/plugin_sort.h"
     "${CMAKE_SOURCE_DIR}/src/api/sorting/plugin_graph.h"
     "${CMAKE_SOURCE_DIR}/src/api/sorting/plugin_sorting_data.h"
-    "${CMAKE_SOURCE_DIR}/src/api/helpers/collections.h"
     "${CMAKE_SOURCE_DIR}/src/api/helpers/crc.h"
     "${CMAKE_SOURCE_DIR}/src/api/helpers/logging.h"
     "${CMAKE_SOURCE_DIR}/src/api/helpers/text.h")
diff --git a/src/api/helpers/collections.h b/src/api/helpers/collections.h
deleted file mode 100644
index cea9d45c..00000000
--- a/src/api/helpers/collections.h
+++ /dev/null
@@ -1,50 +0,0 @@
-/*  LOOT
-
-    A load order optimisation tool for Oblivion, Skyrim, Fallout 3 and
-    Fallout: New Vegas.
-
-    Copyright (C) 2012-2016    WrinklyNinja
-
-    This file is part of LOOT.
-
-    LOOT is free software: you can redistribute
-    it and/or modify it under the terms of the GNU General Public License
-    as published by the Free Software Foundation, either version 3 of
-    the License, or (at your option) any later version.
-
-    LOOT is distributed in the hope that it will
-    be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with LOOT.  If not, see
-    <https://www.gnu.org/licenses/>.
-    */
-
-#ifndef LOOT_API_HELPERS_COLLECTIONS
-#define LOOT_API_HELPERS_COLLECTIONS
-
-#include <vector>
-
-namespace loot {
-// Append second to first, skipping any elements that are already present in
-// first. Although this is O(U * M), both input vectors are expected to be
-// small (with tens of elements being an unusually large number).
-template<typename T>
-std::vector<T> mergeVectors(std::vector<T> first,
-                            const std::vector<T>& second) {
-  const auto initialSizeOfFirst = first.size();
-  for (const auto& element : second) {
-    const auto end = first.cbegin() + initialSizeOfFirst;
-
-    if (std::find(first.cbegin(), end, element) == end) {
-      first.push_back(element);
-    }
-  }
-
-  return first;
-}
-}
-
-#endif
diff --git a/src/api/metadata/conditional_metadata.cpp b/src/api/metadata/conditional_metadata.cpp
index 53fb452b..f778f686 100644
--- a/src/api/metadata/conditional_metadata.cpp
+++ b/src/api/metadata/conditional_metadata.cpp
@@ -24,10 +24,6 @@
 
 #include "loot/metadata/conditional_metadata.h"
 
-#include "api/game/game.h"
-#include "api/helpers/logging.h"
-#include "api/metadata/condition_evaluator.h"
-
 namespace loot {
 ConditionalMetadata::ConditionalMetadata(const std::string& condition) :
     condition_(condition) {}
diff --git a/src/api/metadata/file.cpp b/src/api/metadata/file.cpp
index f6cb5039..132ec0fa 100644
--- a/src/api/metadata/file.cpp
+++ b/src/api/metadata/file.cpp
@@ -24,9 +24,6 @@
 
 #include "loot/metadata/file.h"
 
-#include "api/helpers/text.h"
-#include "api/metadata/yaml/file.h"
-
 namespace loot {
 File::File(const std::string& name,
            const std::string& display,
diff --git a/src/api/metadata/group.cpp b/src/api/metadata/group.cpp
index 135ff63c..a3117f16 100644
--- a/src/api/metadata/group.cpp
+++ b/src/api/metadata/group.cpp
@@ -24,8 +24,6 @@
 
 #include "loot/metadata/group.h"
 
-#include "api/metadata/yaml/group.h"
-
 namespace loot {
 Group::Group(const std::string& name,
              const std::vector<std::string>& afterGroups,
diff --git a/src/api/metadata/message.cpp b/src/api/metadata/message.cpp
index f43abfd3..ca152ab2 100644
--- a/src/api/metadata/message.cpp
+++ b/src/api/metadata/message.cpp
@@ -24,9 +24,7 @@
 
 #include "loot/metadata/message.h"
 
-#include <boost/algorithm/string.hpp>
-
-#include "api/game/game.h"
+#include <stdexcept>
 
 namespace loot {
 Message::Message(const MessageType type,
diff --git a/src/api/metadata/message_content.cpp b/src/api/metadata/message_content.cpp
index 3c145e88..4458551a 100644
--- a/src/api/metadata/message_content.cpp
+++ b/src/api/metadata/message_content.cpp
@@ -24,9 +24,6 @@
 
 #include "loot/metadata/message_content.h"
 
-#include <boost/algorithm/string.hpp>
-#include <optional>
-
 namespace loot {
 MessageContent::MessageContent(const std::string& text,
                                const std::string& language) :
diff --git a/src/api/metadata/plugin_cleaning_data.cpp b/src/api/metadata/plugin_cleaning_data.cpp
index f9a3e880..8dc5d9fc 100644
--- a/src/api/metadata/plugin_cleaning_data.cpp
+++ b/src/api/metadata/plugin_cleaning_data.cpp
@@ -24,10 +24,6 @@
 
 #include "loot/metadata/plugin_cleaning_data.h"
 
-#include "api/game/game.h"
-#include "api/helpers/crc.h"
-#include "api/helpers/logging.h"
-
 namespace loot {
 PluginCleaningData::PluginCleaningData(uint32_t crc,
                                        const std::string& utility) :
diff --git a/src/api/metadata/plugin_metadata.cpp b/src/api/metadata/plugin_metadata.cpp
index 21e63b09..9737d7d9 100644
--- a/src/api/metadata/plugin_metadata.cpp
+++ b/src/api/metadata/plugin_metadata.cpp
@@ -24,15 +24,31 @@
 
 #include "loot/metadata/plugin_metadata.h"
 
-#include <boost/algorithm/string.hpp>
 #include <regex>
 
-#include "api/game/game.h"
-#include "api/helpers/collections.h"
-#include "api/helpers/logging.h"
 #include "api/helpers/text.h"
 #include "api/metadata/yaml/plugin_metadata.h"
 
+namespace {
+// Append second to first, skipping any elements that are already present in
+// first. Although this is O(U * M), both input vectors are expected to be
+// small (with tens of elements being an unusually large number).
+template<typename T>
+std::vector<T> mergeVectors(std::vector<T> first,
+                            const std::vector<T>& second) {
+  const auto initialSizeOfFirst = first.size();
+  for (const auto& element : second) {
+    const auto end = first.cbegin() + initialSizeOfFirst;
+
+    if (std::find(first.cbegin(), end, element) == end) {
+      first.push_back(element);
+    }
+  }
+
+  return first;
+}
+}
+
 namespace loot {
 PluginMetadata::PluginMetadata(const std::string& n) : name_(n) {
   // If the name passed ends in '.ghost', that should be trimmed.
diff --git a/src/api/metadata/tag.cpp b/src/api/metadata/tag.cpp
index ad056a72..1a551ad5 100644
--- a/src/api/metadata/tag.cpp
+++ b/src/api/metadata/tag.cpp
@@ -24,8 +24,6 @@
 
 #include "loot/metadata/tag.h"
 
-#include <boost/algorithm/string.hpp>
-
 namespace loot {
 Tag::Tag(const std::string& tag,
          const bool isAddition,
diff --git a/src/api/sorting/undefined_group_error.cpp b/src/api/sorting/undefined_group_error.cpp
index 293ac857..c955d1ce 100644
--- a/src/api/sorting/undefined_group_error.cpp
+++ b/src/api/sorting/undefined_group_error.cpp
@@ -23,8 +23,6 @@
     */
 #include "loot/exception/undefined_group_error.h"
 
-#include "api/sorting/plugin_graph.h"
-
 namespace loot {
 UndefinedGroupError::UndefinedGroupError(const std::string& groupName) :
       std::runtime_error("The group \"" + groupName + "\" does not exist"),