diff --git a/src/file_io.cpp b/src/file_io.cpp
index a5be9c3..374d90c 100644
--- a/src/file_io.cpp
+++ b/src/file_io.cpp
@@ -38,7 +38,7 @@ namespace gz {
                 getline(file, line);
 
                 // ignore commented lines
-                if (line.find("#") != std::string::npos) { continue; }
+                if (line.starts_with('#')) { continue; }
 
                 // if "=" in line: split into key - value pair and store in map
                 if (line.find("=") != std::string::npos) {
diff --git a/src/file_io.hpp b/src/file_io.hpp
index b43ce67..a05c521 100644
--- a/src/file_io.hpp
+++ b/src/file_io.hpp
@@ -11,6 +11,7 @@ namespace gz {
      * @details
      *  This template function is instantiated for the default unordered_map<string, string> and the util::string_map from util/string.hpp
      * @throws FileIOError
+     * @see @ref fio_t_key_value "Key-Value filetype"
      */
     template<typename Hash, typename Pred>
     bool writeKeyValueFile(const std::string& filepath, const std::unordered_map<std::string, std::string, Hash, Pred>& content);
@@ -18,7 +19,27 @@ namespace gz {
     /**
      * @brief Read a file that contains key = value pairs
      * @throws FileIOError
+     * @see @ref fio_t_key_value "Key-Value filetype"
      */
     std::unordered_map<std::string, std::string> readKeyValueFile(const std::string& filepath, bool removeSpaces=false);
-
 }
+
+/**
+ * @file
+ * @brief Contains file reading/writing utility
+ */
+/**
+ * @page FileIO
+ * @section fio_filetypes Filetypes
+ *  @subsection fio_t_key_value Simple Key-Value file
+ *   A file that contains key - value pairs in each line, separated with "=".
+ *   Any number of whitespaces around the separator is allowed.
+ *   If the first character of a line is "#", the whole line is a comment.
+ *   Example:
+ *   @code
+ *    key1 = value1
+ *    # this is a comment
+ *    key2=  #this_is_value_not_a_comment
+ *    arr = val1, val2, val3
+ *   @endcode
+ */