GL_ENABLE_GET_PROC_ADDRESS=1 is necessary with the latest version of emscripten, see https://github.com/emscripten-core/emscripten/pull/20802

Working-for-Web-(HTML5).md

@@ -259,7 +259,7 @@ Included this snippet at the top of `CMakeLists.txt`, with no changes whatsoever
 
 ```
 if (EMSCRIPTEN)
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -s USE_GLFW=3 -s ASSERTIONS=1 -s WASM=1 -s ASYNCIFY")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -s USE_GLFW=3 -s ASSERTIONS=1 -s WASM=1 -s ASYNCIFY -s GL_ENABLE_GET_PROC_ADDRESS=1")
   set(CMAKE_EXECUTABLE_SUFFIX ".html") # This line is used to set your executable to build with the emscripten html template so taht you can directly open it.
 endif ()
 ```