diff --git a/src/filesys.h b/src/filesys.h
index a2f7b749c..3f2b81d54 100644
--- a/src/filesys.h
+++ b/src/filesys.h
@@ -36,22 +36,23 @@ struct DirListNode
 	bool dir;
 };
 
+[[nodiscard]]
 std::vector<DirListNode> GetDirListing(const std::string &path);
 
 // Returns true if already exists
 bool CreateDir(const std::string &path);
 
-bool PathExists(const std::string &path);
+[[nodiscard]] bool PathExists(const std::string &path);
 
-bool IsPathAbsolute(const std::string &path);
+[[nodiscard]] bool IsPathAbsolute(const std::string &path);
 
-bool IsDir(const std::string &path);
+[[nodiscard]] bool IsDir(const std::string &path);
 
-bool IsExecutable(const std::string &path);
+[[nodiscard]] bool IsExecutable(const std::string &path);
 
-bool IsFile(const std::string &path);
+[[nodiscard]] bool IsFile(const std::string &path);
 
-inline bool IsDirDelimiter(char c)
+[[nodiscard]] inline bool IsDirDelimiter(char c)
 {
 	return c == '/' || c == DIR_DELIM_CHAR;
 }
@@ -64,20 +65,21 @@ bool DeleteSingleFileOrEmptyDirectory(const std::string &path);
 /// Returns path to temp directory.
 /// You probably don't want to use this directly, see `CreateTempFile` or `CreateTempDir`.
 /// @return path or "" on error
-std::string TempPath();
+[[nodiscard]] std::string TempPath();
 
 /// Returns path to securely-created temporary file (will already exist when this function returns).
 /// @return path or "" on error
-std::string CreateTempFile();
+[[nodiscard]] std::string CreateTempFile();
 
 /// Returns path to securely-created temporary directory (will already exist when this function returns).
 /// @return path or "" on error
-std::string CreateTempDir();
+[[nodiscard]] std::string CreateTempDir();
 
 /* Returns a list of subdirectories, including the path itself, but excluding
        hidden directories (whose names start with . or _)
 */
 void GetRecursiveDirs(std::vector<std::string> &dirs, const std::string &dir);
+[[nodiscard]]
 std::vector<std::string> GetRecursiveDirs(const std::string &dir);
 
 /* Multiplatform */
@@ -128,16 +130,19 @@ std::string RemoveRelativePathComponents(std::string path);
 
 // Returns the absolute path for the passed path, with "." and ".." path
 // components and symlinks removed.  Returns "" on error.
+[[nodiscard]]
 std::string AbsolutePath(const std::string &path);
 
 // This is a combination of RemoveRelativePathComponents() and AbsolutePath()
 // It will resolve symlinks for the leading path components that exist and
 // still remove "." and ".." in the rest of the path.
 // Returns "" on error.
+[[nodiscard]]
 std::string AbsolutePathPartial(const std::string &path);
 
 // Returns the filename from a path or the entire path if no directory
 // delimiter is found.
+[[nodiscard]]
 const char *GetFilenameFromPath(const char *path);
 
 // Replace the content of a file on disk in a way that is safe from
@@ -180,6 +185,7 @@ bool OpenStream(std::filebuf &stream, const char *filename,
  * @param mode additional mode bits (e.g. std::ios::app)
  * @return file stream, will be !good in case of error
 */
+[[nodiscard]]
 inline std::ofstream open_ofstream(const char *name, bool log,
 	std::ios::openmode mode = std::ios::openmode())
 {
@@ -202,6 +208,7 @@ inline std::ofstream open_ofstream(const char *name, bool log,
  * @param mode additional mode bits (e.g. std::ios::ate)
  * @return file stream, will be !good in case of error
 */
+[[nodiscard]]
 inline std::ifstream open_ifstream(const char *name, bool log,
 	std::ios::openmode mode = std::ios::openmode())
 {
diff --git a/src/porting.h b/src/porting.h
index 7c652663a..f7d623d33 100644
--- a/src/porting.h
+++ b/src/porting.h
@@ -77,7 +77,7 @@ namespace porting
 void signal_handler_init();
 // Returns a pointer to a bool.
 // When the bool is true, program should quit.
-bool * signal_handler_killstatus();
+[[nodiscard]] bool *signal_handler_killstatus();
 
 /*
 	Path of static data directory.
@@ -105,11 +105,13 @@ extern std::string path_cache;
 /*
 	Gets the path of our executable.
 */
+[[nodiscard]]
 bool getCurrentExecPath(char *buf, size_t len);
 
 /*
 	Concatenate subpath to path_share.
 */
+[[nodiscard]]
 std::string getDataPath(const char *subpath);
 
 /*
@@ -280,7 +282,8 @@ inline const char *getPlatformName()
 	;
 }
 
-bool secure_rand_fill_buf(void *buf, size_t len);
+// Securely fills buffer with bytes from system's random source
+[[nodiscard]] bool secure_rand_fill_buf(void *buf, size_t len);
 
 // Call once near beginning of main function.
 void osSpecificInit();
@@ -308,10 +311,10 @@ static inline void TriggerMemoryTrim() { (void)0; }
 
 #ifdef _WIN32
 // Quotes an argument for use in a CreateProcess() commandline (not cmd.exe!!)
-std::string QuoteArgv(const std::string &arg);
+[[nodiscard]] std::string QuoteArgv(const std::string &arg);
 
 // Convert an error code (e.g. from GetLastError()) into a string.
-std::string ConvertError(DWORD error_code);
+[[nodiscard]] std::string ConvertError(DWORD error_code);
 #endif
 
 // snprintf wrapper
diff --git a/src/util/base64.h b/src/util/base64.h
index 3846d3a25..9cdf5ebc5 100644
--- a/src/util/base64.h
+++ b/src/util/base64.h
@@ -31,6 +31,6 @@ René Nyffenegger rene.nyffenegger@adp-gmbh.ch
 #include <string>
 #include <string_view>
 
-bool base64_is_valid(std::string_view s);
-std::string base64_encode(std::string_view s);
-std::string base64_decode(std::string_view s);
+[[nodiscard]] bool base64_is_valid(std::string_view s);
+[[nodiscard]] std::string base64_encode(std::string_view s);
+[[nodiscard]] std::string base64_decode(std::string_view s);
diff --git a/src/util/colorize.h b/src/util/colorize.h
index cb7ae7c30..924bf7a78 100644
--- a/src/util/colorize.h
+++ b/src/util/colorize.h
@@ -37,6 +37,6 @@ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  *
  * Throws an exception if the url is invalid.
  */
-std::string colorize_url(const std::string &url);
+[[nodiscard]] std::string colorize_url(const std::string &url);
 
 #endif
diff --git a/src/util/enum_string.h b/src/util/enum_string.h
index 5c084c718..08de0b7e2 100644
--- a/src/util/enum_string.h
+++ b/src/util/enum_string.h
@@ -24,4 +24,4 @@ bool string_to_enum(const EnumString *spec, T &result, std::string_view str)
 	return ret;
 }
 
-const char *enum_to_string(const EnumString *spec, int num);
+[[nodiscard]] const char *enum_to_string(const EnumString *spec, int num);
diff --git a/src/util/hex.h b/src/util/hex.h
index c528fe4bd..7a5d761a8 100644
--- a/src/util/hex.h
+++ b/src/util/hex.h
@@ -9,6 +9,7 @@
 
 static const char hex_chars[] = "0123456789abcdef";
 
+[[nodiscard]]
 static inline std::string hex_encode(std::string_view data)
 {
 	std::string ret;
@@ -20,6 +21,7 @@ static inline std::string hex_encode(std::string_view data)
 	return ret;
 }
 
+[[nodiscard]]
 static inline std::string hex_encode(const char *data, size_t data_size)
 {
 	if (!data_size)
diff --git a/src/util/ieee_float.h b/src/util/ieee_float.h
index f3f6de442..316d0589e 100644
--- a/src/util/ieee_float.h
+++ b/src/util/ieee_float.h
@@ -13,7 +13,7 @@ enum FloatType
 	FLOATTYPE_SYSTEM
 };
 
-f32 u32Tof32Slow(u32 i);
-u32 f32Tou32Slow(f32 f);
+[[nodiscard]] f32 u32Tof32Slow(u32 i);
+[[nodiscard]] u32 f32Tou32Slow(f32 f);
 
 FloatType getFloatSerializationType();
diff --git a/src/util/numeric.h b/src/util/numeric.h
index 60d86064f..cacb01621 100644
--- a/src/util/numeric.h
+++ b/src/util/numeric.h
@@ -17,6 +17,7 @@
 
 // Like std::clamp but allows mismatched types
 template <typename T, typename T2, typename T3>
+[[nodiscard]]
 inline constexpr T rangelim(const T &d, const T2 &min, const T3 &max)
 {
 	if (d < (T)min)
@@ -88,7 +89,6 @@ inline void getContainerPosWithOffset(const v3s16 &p, s16 d, v3s16 &container, v
 	getContainerPosWithOffset(p.Z, d, container.Z, offset.Z);
 }
 
-
 inline bool isInArea(v3s16 p, s16 d)
 {
 	return (
@@ -193,6 +193,7 @@ struct MeshGrid {
  *  \note This is also used in cases where degrees wrapped to the range [0, 360]
  *  is innapropriate (e.g. pitch needs negative values)
  */
+[[nodiscard]]
 inline float modulo360f(float f)
 {
 	return fmodf(f, 360.0f);
@@ -201,6 +202,7 @@ inline float modulo360f(float f)
 
 /** Returns \p f wrapped to the range [0, 360]
   */
+[[nodiscard]]
 inline float wrapDegrees_0_360(float f)
 {
 	float value = modulo360f(f);
@@ -210,6 +212,7 @@ inline float wrapDegrees_0_360(float f)
 
 /** Returns \p v3f wrapped to the range [0, 360]
   */
+[[nodiscard]]
 inline v3f wrapDegrees_0_360_v3f(v3f v)
 {
 	v3f value_v3f;
@@ -227,6 +230,7 @@ inline v3f wrapDegrees_0_360_v3f(v3f v)
 
 /** Returns \p f wrapped to the range [-180, 180]
   */
+[[nodiscard]]
 inline float wrapDegrees_180(float f)
 {
 	float value = modulo360f(f + 180);
@@ -289,6 +293,7 @@ inline u32 calc_parity(u32 v)
  * @param seed initial seed value
  * @return hash value
  */
+[[nodiscard]]
 u64 murmur_hash_64_ua(const void *key, size_t len, unsigned int seed);
 
 /**
@@ -299,7 +304,7 @@ u64 murmur_hash_64_ua(const void *key, size_t len, unsigned int seed);
  * @param distance_ptr return location for distance from the camera
  */
 bool isBlockInSight(v3s16 blockpos_b, v3f camera_pos, v3f camera_dir,
-		f32 camera_fov, f32 range, f32 *distance_ptr=NULL);
+		f32 camera_fov, f32 range, f32 *distance_ptr=nullptr);
 
 s16 adjustDist(s16 dist, float zoom_fov);
 
@@ -307,12 +312,14 @@ s16 adjustDist(s16 dist, float zoom_fov);
 	Returns nearest 32-bit integer for given floating point number.
 	<cmath> and <math.h> in VC++ don't provide round().
 */
+[[nodiscard]]
 inline s32 myround(f32 f)
 {
 	return (s32)(f < 0.f ? (f - 0.5f) : (f + 0.5f));
 }
 
 template <typename T>
+[[nodiscard]]
 inline constexpr T sqr(T f)
 {
 	return f * f;
@@ -321,6 +328,7 @@ inline constexpr T sqr(T f)
 /*
 	Returns integer position of node in given floating point position
 */
+[[nodiscard]]
 inline v3s16 floatToInt(v3f p, f32 d)
 {
 	return v3s16(
@@ -332,6 +340,7 @@ inline v3s16 floatToInt(v3f p, f32 d)
 /*
 	Returns integer position of node in given double precision position
  */
+[[nodiscard]]
 inline v3s16 doubleToInt(v3d p, double d)
 {
 	return v3s16(
@@ -343,12 +352,14 @@ inline v3s16 doubleToInt(v3d p, double d)
 /*
 	Returns floating point position of node in given integer position
 */
+[[nodiscard]]
 inline v3f intToFloat(v3s16 p, f32 d)
 {
 	return v3f::from(p) * d;
 }
 
-// Random helper. Usually d=BS
+// Returns box of a node as in-world box. Usually d=BS
+[[nodiscard]]
 inline aabb3f getNodeBox(v3s16 p, float d)
 {
 	return aabb3f(
@@ -368,6 +379,7 @@ public:
 		@param wanted_interval interval wanted
 		@return true if action should be done
 	*/
+	[[nodiscard]]
 	bool step(float dtime, float wanted_interval)
 	{
 		m_accumulator += dtime;
@@ -489,12 +501,14 @@ inline video::SColor multiplyColorValue(const video::SColor &color, float mod)
 			core::clamp<u32>(color.getBlue() * mod, 0, 255));
 }
 
-template <typename T> constexpr inline T numericAbsolute(T v)
+template <typename T>
+constexpr inline T numericAbsolute(T v)
 {
 	return v < 0 ? T(-v) : v;
 }
 
-template <typename T> constexpr inline T numericSign(T v)
+template <typename T>
+constexpr inline T numericSign(T v)
 {
 	return T(v < 0 ? -1 : (v == 0 ? 0 : 1));
 }
diff --git a/src/util/serialize.h b/src/util/serialize.h
index b12d551ac..7da5f44d6 100644
--- a/src/util/serialize.h
+++ b/src/util/serialize.h
@@ -435,12 +435,12 @@ MAKE_STREAM_WRITE_FXN(video::SColor, ARGB8, 4);
 //// More serialization stuff
 ////
 
-inline float clampToF1000(float v)
+[[nodiscard]] inline float clampToF1000(float v)
 {
 	return core::clamp(v, F1000_MIN, F1000_MAX);
 }
 
-inline v3f clampToF1000(v3f v)
+[[nodiscard]] inline v3f clampToF1000(v3f v)
 {
 	return {clampToF1000(v.X), clampToF1000(v.Y), clampToF1000(v.Z)};
 }
diff --git a/src/util/string.h b/src/util/string.h
index eaa13a264..3dcbfe85f 100644
--- a/src/util/string.h
+++ b/src/util/string.h
@@ -72,8 +72,8 @@ struct FlagDesc {
 
 // Try to avoid converting between wide and UTF-8 unless you need to
 // input/output stuff via Irrlicht
-std::wstring utf8_to_wide(std::string_view input);
-std::string wide_to_utf8(std::wstring_view input);
+[[nodiscard]] std::wstring utf8_to_wide(std::string_view input);
+[[nodiscard]] std::string wide_to_utf8(std::wstring_view input);
 
 void wide_add_codepoint(std::wstring &result, char32_t codepoint);
 
@@ -287,6 +287,7 @@ MAKE_VARIANT(str_ends_with, std::basic_string_view<T>, const T*)
  * @return An std::vector<std::basic_string<T> > of the component parts
  */
 template <typename T>
+[[nodiscard]]
 inline std::vector<std::basic_string<T> > str_split(
 		const std::basic_string<T> &str,
 		T delimiter)
@@ -306,6 +307,7 @@ inline std::vector<std::basic_string<T> > str_split(
  * @param str
  * @return A copy of \p str converted to all lowercase characters.
  */
+[[nodiscard]]
 inline std::string lowercase(std::string_view str)
 {
 	std::string s2;
@@ -331,6 +333,7 @@ inline bool my_isspace(const wchar_t c)
  * @return A view of \p str with leading and trailing whitespace removed.
  */
 template<typename T>
+[[nodiscard]]
 inline std::basic_string_view<T> trim(std::basic_string_view<T> str)
 {
 	size_t front = 0;
@@ -354,6 +357,7 @@ inline std::basic_string_view<T> trim(std::basic_string_view<T> str)
  * @return A copy of \p str with leading and trailing whitespace removed.
  */
 template<typename T>
+[[nodiscard]]
 inline std::basic_string<T> trim(std::basic_string<T> &&str)
 {
 	std::basic_string<T> ret(trim(std::basic_string_view<T>(str)));
@@ -361,6 +365,7 @@ inline std::basic_string<T> trim(std::basic_string<T> &&str)
 }
 
 template<typename T>
+[[nodiscard]]
 inline std::basic_string_view<T> trim(const std::basic_string<T> &str)
 {
 	return trim(std::basic_string_view<T>(str));
@@ -368,6 +373,7 @@ inline std::basic_string_view<T> trim(const std::basic_string<T> &str)
 
 // The above declaration causes ambiguity with char pointers so we have to fix that:
 template<typename T>
+[[nodiscard]]
 inline std::basic_string_view<T> trim(const T *str)
 {
 	return trim(std::basic_string_view<T>(str));
@@ -556,6 +562,7 @@ std::string wrap_rows(std::string_view from, unsigned row_len, bool has_color_co
  * Removes backslashes from an escaped string (FormSpec strings)
  */
 template <typename T>
+[[nodiscard]]
 inline std::basic_string<T> unescape_string(const std::basic_string<T> &s)
 {
 	std::basic_string<T> res;
@@ -580,6 +587,7 @@ inline std::basic_string<T> unescape_string(const std::basic_string<T> &s)
  * @return \p s, with escape sequences removed.
  */
 template <typename T>
+[[nodiscard]]
 std::basic_string<T> unescape_enriched(const std::basic_string<T> &s)
 {
 	std::basic_string<T> output;
@@ -610,6 +618,7 @@ std::basic_string<T> unescape_enriched(const std::basic_string<T> &s)
 }
 
 template <typename T>
+[[nodiscard]]
 std::vector<std::basic_string<T> > split(const std::basic_string<T> &s, T delim)
 {
 	std::vector<std::basic_string<T> > tokens;
@@ -641,10 +650,13 @@ std::vector<std::basic_string<T> > split(const std::basic_string<T> &s, T delim)
 	return tokens;
 }
 
+[[nodiscard]]
 std::wstring translate_string(std::wstring_view s, Translations *translations);
 
+[[nodiscard]]
 std::wstring translate_string(std::wstring_view s);
 
+[[nodiscard]]
 inline std::wstring unescape_translate(std::wstring_view s)
 {
 	return unescape_enriched(translate_string(s));
@@ -730,6 +742,7 @@ inline const std::string duration_to_string(int sec)
  *
  * @return A std::string
  */
+[[nodiscard]]
 inline std::string str_join(const std::vector<std::string> &list,
 		std::string_view delimiter)
 {
@@ -748,6 +761,7 @@ inline std::string str_join(const std::vector<std::string> &list,
 /**
  * Create a UTF8 std::string from an irr::core::stringw.
  */
+[[nodiscard]]
 inline std::string stringw_to_utf8(const irr::core::stringw &input)
 {
 	std::wstring_view sv(input.c_str(), input.size());
@@ -757,6 +771,7 @@ inline std::string stringw_to_utf8(const irr::core::stringw &input)
 /**
  * Create an irr::core:stringw from a UTF8 std::string.
  */
+[[nodiscard]]
 inline irr::core::stringw utf8_to_stringw(std::string_view input)
 {
 	std::wstring str = utf8_to_wide(input);
@@ -770,6 +785,7 @@ inline irr::core::stringw utf8_to_stringw(std::string_view input)
  *    and add a prefix to them
  * 2. Remove 'unsafe' characters from the name by replacing them with '_'
  */
+[[nodiscard]]
 std::string sanitizeDirName(std::string_view str, std::string_view optional_prefix);
 
 /**