diff --git a/chatterino.pro b/chatterino.pro
index 09bd0300..440239ca 100644
--- a/chatterino.pro
+++ b/chatterino.pro
@@ -1,3 +1,16 @@
+# Exposed build flags:
+# from lib/fmt.pri
+#  - FMT_PREFIX ($$PWD by default)
+#  - FMT_SYSTEM (1 = true) (Linux only, uses pkg-config)
+# from lib/websocketpp.pri
+#  - WEBSOCKETPP_PREFIX ($$PWD by default)
+#  - WEBSOCKETPP_SYSTEM (1 = true) (unix only)
+# from lib/rapidjson.pri
+#  - RAPIDJSON_PREFIX ($$PWD by default)
+#  - RAPIDJSON_SYSTEM (1 = true) (Linux only, uses pkg-config)
+# from lib/boost.pri
+#  - BOOST_DIRECTORY (C:\local\boost\ by default) (Windows only)
+
 QT                += widgets core gui network multimedia svg concurrent
 CONFIG            += communi
 COMMUNI           += core model util
@@ -31,6 +44,9 @@ win32-msvc* {
 linux {
     LIBS += -lrt
     QMAKE_LFLAGS += -lrt
+
+    # Enable linking libraries using PKGCONFIG += libraryname
+    CONFIG += link_pkgconfig
 }
 
 macx {
diff --git a/lib/boost.pri b/lib/boost.pri
index 044de1de..bea78de4 100644
--- a/lib/boost.pri
+++ b/lib/boost.pri
@@ -1,3 +1,7 @@
+# boost
+# Exposed build flags:
+#  - BOOST_DIRECTORY (C:\local\boost\ by default) (Windows only)
+
 pajlada {
     BOOST_DIRECTORY = C:\dev\projects\boost_1_66_0\
 }
diff --git a/lib/fmt.pri b/lib/fmt.pri
index 04d34399..8703d2bd 100644
--- a/lib/fmt.pri
+++ b/lib/fmt.pri
@@ -1,4 +1,18 @@
 # fmt
-SOURCES += $$PWD/fmt/fmt/format.cpp
+# Chatterino2 is tested with FMT 4.0
+# Exposed build flags:
+#  - FMT_PREFIX ($$PWD by default)
+#  - FMT_SYSTEM (1 = true) (Linux only, uses pkg-config)
 
-INCLUDEPATH += $$PWD/fmt/
+!defined(FMT_PREFIX) {
+    FMT_PREFIX = $$PWD
+}
+
+linux:equals(FMT_SYSTEM, "1") {
+    message("Building with system FMT")
+    PKGCONFIG += fmt
+} else {
+    SOURCES += $$FMT_PREFIX/fmt/fmt/format.cpp
+
+    INCLUDEPATH += $$PWD/fmt/
+}
diff --git a/lib/rapidjson.pri b/lib/rapidjson.pri
index 5b614e23..131f0401 100644
--- a/lib/rapidjson.pri
+++ b/lib/rapidjson.pri
@@ -1,2 +1,15 @@
 # rapidjson
-INCLUDEPATH += $$PWD/rapidjson/include/
+# Chatterino2 is tested with RapidJSON v1.1.0
+#  - RAPIDJSON_PREFIX ($$PWD by default)
+#  - RAPIDJSON_SYSTEM (1 = true) (Linux only, uses pkg-config)
+
+!defined(RAPIDJSON_PREFIX) {
+    RAPIDJSON_PREFIX = $$PWD
+}
+
+linux:equals(RAPIDJSON_SYSTEM, "1") {
+    message("Building with system RapidJSON")
+    PKGCONFIG += RapidJSON
+} else {
+    INCLUDEPATH += $$RAPIDJSON_PREFIX/rapidjson/include/
+}
diff --git a/lib/websocketpp.pri b/lib/websocketpp.pri
index ae3ea1e4..2ae1289b 100644
--- a/lib/websocketpp.pri
+++ b/lib/websocketpp.pri
@@ -1 +1,20 @@
-INCLUDEPATH += $$PWD/../lib/websocketpp
+# websocketpp
+# Chatterino2 is tested with websocketpp 0.8.1
+# Exposed build flags:
+#  - WEBSOCKETPP_PREFIX ($$PWD by default)
+#  - WEBSOCKETPP_SYSTEM (1 = true) (unix only)
+
+!defined(WEBSOCKETPP_PREFIX) {
+    WEBSOCKETPP_PREFIX = $$PWD
+}
+
+unix {
+    equals(WEBSOCKETPP_SYSTEM, "1") {
+        message("Building with system websocketpp")
+    } else {
+        message("Building with websocketpp submodule (Prefix: $$WEBSOCKETPP_PREFIX)")
+        INCLUDEPATH += $$WEBSOCKETPP_PREFIX/websocketpp/
+    }
+} else {
+    INCLUDEPATH += $$WEBSOCKETPP_PREFIX/websocketpp
+}