diff --git a/src/console_cmds.cpp b/src/console_cmds.cpp
index bc3a4434fa..267fa1b5d7 100644
--- a/src/console_cmds.cpp
+++ b/src/console_cmds.cpp
@@ -1899,9 +1899,7 @@ static void OutputContentState(const ContentInfo *const ci)
 	static const char * const states[] = { "Not selected", "Selected", "Dep Selected", "Installed", "Unknown" };
 	static const TextColour state_to_colour[] = { CC_COMMAND, CC_INFO, CC_INFO, CC_WHITE, CC_ERROR };
 
-	char buf[sizeof(ci->md5sum) * 2 + 1];
-	md5sumToString(buf, lastof(buf), ci->md5sum);
-	IConsolePrint(state_to_colour[ci->state], "{}, {}, {}, {}, {:08X}, {}", ci->id, types[ci->type - 1], states[ci->state], ci->name, ci->unique_id, buf);
+	IConsolePrint(state_to_colour[ci->state], "{}, {}, {}, {}, {:08X}, {}", ci->id, types[ci->type - 1], states[ci->state], ci->name, ci->unique_id, MD5SumToString(ci->md5sum));
 }
 
 DEF_CONSOLE_CMD(ConContent)
diff --git a/src/gamelog.cpp b/src/gamelog.cpp
index 8477ab90cd..6a4632fcb7 100644
--- a/src/gamelog.cpp
+++ b/src/gamelog.cpp
@@ -125,9 +125,7 @@ template <typename T>
 static void AddGrfInfo(T &outputIterator, uint grfid, const uint8 *md5sum, const GRFConfig *gc)
 {
 	if (md5sum != nullptr) {
-		char txt[40];
-		md5sumToString(txt, lastof(txt), md5sum);
-		fmt::format_to(outputIterator, "GRF ID {:08X}, checksum {}", BSWAP32(grfid), txt);
+		fmt::format_to(outputIterator, "GRF ID {:08X}, checksum {}", BSWAP32(grfid), MD5SumToString(md5sum));
 	} else {
 		fmt::format_to(outputIterator, "GRF ID {:08X}", BSWAP32(grfid));
 	}
diff --git a/src/network/network_client.cpp b/src/network/network_client.cpp
index 3bfdaa118d..6ffecebe1e 100644
--- a/src/network/network_client.cpp
+++ b/src/network/network_client.cpp
@@ -666,9 +666,7 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_CHECK_NEWGRFS(P
 		const GRFConfig *f = FindGRFConfig(c.grfid, FGCM_EXACT, c.md5sum);
 		if (f == nullptr) {
 			/* We do not know this GRF, bail out of initialization */
-			char buf[sizeof(c.md5sum) * 2 + 1];
-			md5sumToString(buf, lastof(buf), c.md5sum);
-			Debug(grf, 0, "NewGRF {:08X} not found; checksum {}", BSWAP32(c.grfid), buf);
+			Debug(grf, 0, "NewGRF {:08X} not found; checksum {}", BSWAP32(c.grfid), MD5SumToString(c.md5sum));
 			ret = NETWORK_RECV_STATUS_NEWGRF_MISMATCH;
 		}
 	}
diff --git a/src/network/network_content_gui.cpp b/src/network/network_content_gui.cpp
index dcafc80112..3f8c97e348 100644
--- a/src/network/network_content_gui.cpp
+++ b/src/network/network_content_gui.cpp
@@ -365,9 +365,7 @@ class NetworkContentListWindow : public Window, ContentCallback {
 				if (!first) url.push_back(',');
 				first = false;
 
-				char buf[33];
-				md5sumToString(buf, lastof(buf), ci->md5sum);
-				fmt::format_to(std::back_inserter(url), "{:08X}:{}", ci->unique_id, buf);
+				fmt::format_to(std::back_inserter(url), "{:08X}:{}", ci->unique_id, MD5SumToString(ci->md5sum));
 			}
 		} else {
 			url += "do=searchtext&q=";
diff --git a/src/newgrf_config.cpp b/src/newgrf_config.cpp
index 0391e2c000..d51bb48a5b 100644
--- a/src/newgrf_config.cpp
+++ b/src/newgrf_config.cpp
@@ -517,14 +517,11 @@ GRFListCompatibility IsGoodGRFConfigList(GRFConfig *grfconfig)
 	for (GRFConfig *c = grfconfig; c != nullptr; c = c->next) {
 		const GRFConfig *f = FindGRFConfig(c->ident.grfid, FGCM_EXACT, c->ident.md5sum);
 		if (f == nullptr || HasBit(f->flags, GCF_INVALID)) {
-			char buf[256];
-
 			/* If we have not found the exactly matching GRF try to find one with the
 			 * same grfid, as it most likely is compatible */
 			f = FindGRFConfig(c->ident.grfid, FGCM_COMPATIBLE, nullptr, c->version);
 			if (f != nullptr) {
-				md5sumToString(buf, lastof(buf), c->ident.md5sum);
-				Debug(grf, 1, "NewGRF {:08X} ({}) not found; checksum {}. Compatibility mode on", BSWAP32(c->ident.grfid), c->filename, buf);
+				Debug(grf, 1, "NewGRF {:08X} ({}) not found; checksum {}. Compatibility mode on", BSWAP32(c->ident.grfid), c->filename, MD5SumToString(c->ident.md5sum));
 				if (!HasBit(c->flags, GCF_COMPATIBLE)) {
 					/* Preserve original_md5sum after it has been assigned */
 					SetBit(c->flags, GCF_COMPATIBLE);
@@ -537,8 +534,7 @@ GRFListCompatibility IsGoodGRFConfigList(GRFConfig *grfconfig)
 			}
 
 			/* No compatible grf was found, mark it as disabled */
-			md5sumToString(buf, lastof(buf), c->ident.md5sum);
-			Debug(grf, 0, "NewGRF {:08X} ({}) not found; checksum {}", BSWAP32(c->ident.grfid), c->filename, buf);
+			Debug(grf, 0, "NewGRF {:08X} ({}) not found; checksum {}", BSWAP32(c->ident.grfid), c->filename, MD5SumToString(c->ident.md5sum));
 
 			c->status = GCS_NOT_FOUND;
 			res = GLC_NOT_FOUND;
diff --git a/src/newgrf_gui.cpp b/src/newgrf_gui.cpp
index 0181556a86..0cd608de4a 100644
--- a/src/newgrf_gui.cpp
+++ b/src/newgrf_gui.cpp
@@ -92,9 +92,8 @@ static void ShowNewGRFInfo(const GRFConfig *c, const Rect &r, bool show_params)
 	}
 
 	/* Prepare and draw GRF ID */
-	char buff[256];
-	seprintf(buff, lastof(buff), "%08X", BSWAP32(c->ident.grfid));
-	SetDParamStr(0, buff);
+	std::string tmp = fmt::format("{:08X}", BSWAP32(c->ident.grfid));
+	SetDParamStr(0, tmp);
 	tr.top = DrawStringMultiLine(tr, STR_NEWGRF_SETTINGS_GRF_ID);
 
 	if ((_settings_client.gui.newgrf_developer_tools || _settings_client.gui.newgrf_show_old_versions) && c->version != 0) {
@@ -107,13 +106,14 @@ static void ShowNewGRFInfo(const GRFConfig *c, const Rect &r, bool show_params)
 	}
 
 	/* Prepare and draw MD5 sum */
-	md5sumToString(buff, lastof(buff), c->ident.md5sum);
-	SetDParamStr(0, buff);
+	tmp = MD5SumToString(c->ident.md5sum);
+	SetDParamStr(0, tmp);
 	tr.top = DrawStringMultiLine(tr, STR_NEWGRF_SETTINGS_MD5SUM);
 
 	/* Show GRF parameter list */
 	if (show_params) {
 		if (c->num_params > 0) {
+			char buff[256];
 			GRFBuildParamList(buff, c, lastof(buff));
 			SetDParam(0, STR_JUST_RAW_STRING);
 			SetDParamStr(1, buff);
diff --git a/src/openttd.cpp b/src/openttd.cpp
index 52a466f78d..97face4e6c 100644
--- a/src/openttd.cpp
+++ b/src/openttd.cpp
@@ -257,9 +257,8 @@ static void WriteSavegameInfo(const char *name)
 	message += "NewGRFs:\n";
 	if (_load_check_data.HasNewGrfs()) {
 		for (GRFConfig *c = _load_check_data.grfconfig; c != nullptr; c = c->next) {
-			char md5sum[33];
-			md5sumToString(md5sum, lastof(md5sum), HasBit(c->flags, GCF_COMPATIBLE) ? c->original_md5sum : c->ident.md5sum);
-			fmt::format_to(std::back_inserter(message), "{:08X} {} {}\n", c->ident.grfid, md5sum, c->filename);
+			fmt::format_to(std::back_inserter(message), "{:08X} {} {}\n", c->ident.grfid,
+				MD5SumToString(HasBit(c->flags, GCF_COMPATIBLE) ? c->original_md5sum : c->ident.md5sum), c->filename);
 		}
 	}
 
diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
index 0b8ae1cff7..822de66802 100644
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -388,16 +388,12 @@ static void CDECL HandleSavegameLoadCrash(int signum)
 		for (const GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
 			if (HasBit(c->flags, GCF_COMPATIBLE)) {
 				const GRFIdentifier *replaced = _gamelog.GetOverriddenIdentifier(c);
-				char original_md5[40];
-				char replaced_md5[40];
-				md5sumToString(original_md5, lastof(original_md5), c->original_md5sum);
-				md5sumToString(replaced_md5, lastof(replaced_md5), replaced->md5sum);
-				fmt::format_to(std::back_inserter(message), "NewGRF {:08X} (checksum {}) not found.\n  Loaded NewGRF \"{}\" (checksum {}) with same GRF ID instead.\n", BSWAP32(c->ident.grfid), original_md5, c->filename, replaced_md5);
+				fmt::format_to(std::back_inserter(message), "NewGRF {:08X} (checksum {}) not found.\n  Loaded NewGRF \"{}\" (checksum {}) with same GRF ID instead.\n",
+						BSWAP32(c->ident.grfid), MD5SumToString(c->original_md5sum), c->filename, MD5SumToString(replaced->md5sum));
 			}
 			if (c->status == GCS_NOT_FOUND) {
-				char buf[40];
-				md5sumToString(buf, lastof(buf), c->ident.md5sum);
-				fmt::format_to(std::back_inserter(message), "NewGRF {:08X} ({}) not found; checksum {}.\n", BSWAP32(c->ident.grfid), c->filename, buf);
+				fmt::format_to(std::back_inserter(message), "NewGRF {:08X} ({}) not found; checksum {}.\n",
+						BSWAP32(c->ident.grfid), c->filename, MD5SumToString(c->ident.md5sum));
 			}
 		}
 	} else {
diff --git a/src/screenshot.cpp b/src/screenshot.cpp
index f0176b31d5..2f3a8257cb 100644
--- a/src/screenshot.cpp
+++ b/src/screenshot.cpp
@@ -320,9 +320,7 @@ static bool MakePNGImage(const char *name, ScreenshotCallback *callb, void *user
 	fmt::format_to(std::back_inserter(message), "Graphics set: {} ({})\n", BaseGraphics::GetUsedSet()->name, BaseGraphics::GetUsedSet()->version);
 	message += "NewGRFs:\n";
 	for (const GRFConfig *c = _game_mode == GM_MENU ? nullptr : _grfconfig; c != nullptr; c = c->next) {
-		char buf[33];
-		md5sumToString(buf, lastof(buf), c->ident.md5sum);
-		fmt::format_to(std::back_inserter(message), "{:08X} {} {}\n", BSWAP32(c->ident.grfid), buf, c->filename);
+		fmt::format_to(std::back_inserter(message), "{:08X} {} {}\n", BSWAP32(c->ident.grfid), MD5SumToString(c->ident.md5sum), c->filename);
 	}
 	message += "\nCompanies:\n";
 	for (const Company *c : Company::Iterate()) {
diff --git a/src/settings.cpp b/src/settings.cpp
index 6dfd8e240d..d650d5594d 100644
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -1135,14 +1135,11 @@ static void GRFSaveConfig(IniFile &ini, const char *grpname, const GRFConfig *li
 	const GRFConfig *c;
 
 	for (c = list; c != nullptr; c = c->next) {
-		/* Hex grfid (4 bytes in nibbles), "|", hex md5sum (16 bytes in nibbles), "|", file system path. */
-		char key[4 * 2 + 1 + 16 * 2 + 1 + MAX_PATH];
 		char params[512];
 		GRFBuildParamList(params, c, lastof(params));
 
-		char *pos = key + seprintf(key, lastof(key), "%08X|", BSWAP32(c->ident.grfid));
-		pos = md5sumToString(pos, lastof(key), c->ident.md5sum);
-		seprintf(pos, lastof(key), "|%s", c->filename);
+		std::string key = fmt::format("{:08X}|{}|{}", BSWAP32(c->ident.grfid),
+				MD5SumToString(c->ident.md5sum), c->filename);
 		group->GetItem(key, true)->SetValue(params);
 	}
 }
diff --git a/src/string.cpp b/src/string.cpp
index 55a7ad4ced..35b3dc5b3d 100644
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -612,20 +612,12 @@ int CDECL seprintf(char *str, const char *last, const char *format, ...)
 
 /**
  * Convert the md5sum to a hexadecimal string representation
- * @param buf buffer to put the md5sum into
- * @param last last character of buffer (usually lastof(buf))
  * @param md5sum the md5sum itself
- * @return a pointer to the next character after the md5sum
+ * @return the string representation of the md5sum.
  */
-char *md5sumToString(char *buf, const char *last, const uint8 md5sum[16])
+std::string MD5SumToString(const uint8 md5sum[16])
 {
-	char *p = buf;
-
-	for (uint i = 0; i < 16; i++) {
-		p += seprintf(p, last, "%02X", md5sum[i]);
-	}
-
-	return p;
+	return FormatArrayAsHex({md5sum, 16});
 }
 
 
diff --git a/src/string_func.h b/src/string_func.h
index 1abbd470f1..c03101c213 100644
--- a/src/string_func.h
+++ b/src/string_func.h
@@ -86,7 +86,7 @@ static inline size_t ttd_strnlen(const char *str, size_t maxlen)
 	return t - str;
 }
 
-char *md5sumToString(char *buf, const char *last, const uint8 md5sum[16]);
+std::string MD5SumToString(const uint8 md5sum[16]);
 
 bool IsValidChar(WChar key, CharSetFilter afilter);