diff --git a/src/fileio.cpp b/src/fileio.cpp
index 4485b73473..aa1f00bcdb 100644
--- a/src/fileio.cpp
+++ b/src/fileio.cpp
@@ -35,7 +35,7 @@ static bool _do_scan_working_directory = true;
 extern std::string _config_file;
 extern std::string _highscore_file;
 
-static const char * const _subdirs[] = {
+static const std::string_view _subdirs[] = {
 	"",
 	"save" PATHSEP,
 	"save" PATHSEP "autosave" PATHSEP,
@@ -165,7 +165,7 @@ std::string FioGetDirectory(Searchpath sp, Subdirectory subdir)
 	assert(subdir < NUM_SUBDIRS);
 	assert(sp < NUM_SEARCHPATHS);
 
-	return _searchpaths[sp] + _subdirs[subdir];
+	return fmt::format("{}{}", _searchpaths[sp], _subdirs[subdir]);
 }
 
 std::string FioFindDirectory(Subdirectory subdir)
@@ -180,7 +180,7 @@ std::string FioFindDirectory(Subdirectory subdir)
 	return _personal_dir;
 }
 
-static std::optional<FileHandle> FioFOpenFileSp(std::string_view filename, const char *mode, Searchpath sp, Subdirectory subdir, size_t *filesize)
+static std::optional<FileHandle> FioFOpenFileSp(std::string_view filename, std::string_view mode, Searchpath sp, Subdirectory subdir, size_t *filesize)
 {
 #if defined(_WIN32)
 	/* fopen is implemented as a define with ellipses for
@@ -188,7 +188,7 @@ static std::optional<FileHandle> FioFOpenFileSp(std::string_view filename, const
 	 * a string, but a variable, it 'renames' the variable,
 	 * so make that variable to makes it compile happily */
 	wchar_t Lmode[5];
-	MultiByteToWideChar(CP_ACP, 0, mode, -1, Lmode, static_cast<int>(std::size(Lmode)));
+	MultiByteToWideChar(CP_ACP, 0, mode.data(), static_cast<int>(std::size(mode)), Lmode, static_cast<int>(std::size(Lmode)));
 #endif
 	std::string buf;
 
@@ -239,7 +239,7 @@ static std::optional<FileHandle> FioFOpenFileTar(const TarFileListEntry &entry,
  * @param subdir Subdirectory to open.
  * @return File handle of the opened file, or \c nullptr if the file is not available.
  */
-std::optional<FileHandle> FioFOpenFile(std::string_view filename, const char *mode, Subdirectory subdir, size_t *filesize)
+std::optional<FileHandle> FioFOpenFile(std::string_view filename, std::string_view mode, Subdirectory subdir, size_t *filesize)
 {
 	std::optional<FileHandle> f = std::nullopt;
 	assert(subdir < NUM_SUBDIRS || subdir == NO_DIRECTORY);
@@ -658,7 +658,7 @@ bool ExtractTar(const std::string &tar_filename, Subdirectory subdir)
  * @param exe the path from the current path to the executable
  * @note defined in the OS related files (win32.cpp, unix.cpp etc)
  */
-extern void DetermineBasePaths(const char *exe);
+extern void DetermineBasePaths(std::string_view exe);
 #else /* defined(_WIN32) */
 
 /**
@@ -668,9 +668,9 @@ extern void DetermineBasePaths(const char *exe);
  * in the same way we remove the name from the executable name.
  * @param exe the path to the executable
  */
-static bool ChangeWorkingDirectoryToExecutable(const char *exe)
+static bool ChangeWorkingDirectoryToExecutable(std::string_view exe)
 {
-	std::string path = exe;
+	std::string path{exe};
 
 #ifdef WITH_COCOA
 	for (size_t pos = path.find_first_of('.'); pos != std::string::npos; pos = path.find_first_of('.', pos + 1)) {
@@ -746,7 +746,7 @@ static std::string GetHomeDir()
  * Determine the base (personal dir and game data dir) paths
  * @param exe the path to the executable
  */
-void DetermineBasePaths(const char *exe)
+void DetermineBasePaths(std::string_view exe)
 {
 	std::string tmp;
 	const std::string homedir = GetHomeDir();
@@ -874,7 +874,7 @@ std::string _personal_dir;
  * @param exe the path from the current path to the executable
  * @param only_local_path Whether we shouldn't fill searchpaths with global folders.
  */
-void DeterminePaths(const char *exe, bool only_local_path)
+void DeterminePaths(std::string_view exe, bool only_local_path)
 {
 	DetermineBasePaths(exe);
 	FillValidSearchPaths(only_local_path);
@@ -976,7 +976,7 @@ void DeterminePaths(const char *exe, bool only_local_path)
 	};
 
 	for (const auto &default_subdir : default_subdirs) {
-		FioCreateDirectory(_personal_dir + _subdirs[default_subdir]);
+		FioCreateDirectory(fmt::format("{}{}", _personal_dir, _subdirs[default_subdir]));
 	}
 
 	/* If we have network we make a directory for the autodownloading of content */
@@ -1170,7 +1170,7 @@ std::optional<FileHandle> FileHandle::Open(const std::string &filename, std::str
 {
 #if defined(_WIN32)
 	/* Windows also requires mode to be wchar_t. */
-	auto f = _wfopen(OTTD2FS(filename).c_str(), OTTD2FS(mode).c_str());
+	auto f = _wfopen(OTTD2FS(filename).c_str(), OTTD2FS(std::string{mode}).c_str());
 #else
 	auto f = fopen(filename.c_str(), std::string{mode}.c_str());
 #endif /* _WIN32 */
diff --git a/src/fileio_func.h b/src/fileio_func.h
index 34a2b2f1a2..79ab20ca56 100644
--- a/src/fileio_func.h
+++ b/src/fileio_func.h
@@ -13,7 +13,7 @@
 #include "core/enum_type.hpp"
 #include "fileio_type.h"
 
-std::optional<FileHandle> FioFOpenFile(std::string_view filename, const char *mode, Subdirectory subdir, size_t *filesize = nullptr);
+std::optional<FileHandle> FioFOpenFile(std::string_view filename, std::string_view mode, Subdirectory subdir, size_t *filesize = nullptr);
 bool FioCheckFileExists(std::string_view filename, Subdirectory subdir);
 std::string FioFindFullPath(Subdirectory subdir, std::string_view filename);
 std::string FioGetDirectory(Searchpath sp, Subdirectory subdir);
@@ -21,11 +21,11 @@ std::string FioFindDirectory(Subdirectory subdir);
 void FioCreateDirectory(const std::string &name);
 bool FioRemove(const std::string &filename);
 
-const char *FiosGetScreenshotDir();
+std::string_view FiosGetScreenshotDir();
 
 void SanitizeFilename(std::string &filename);
 void AppendPathSeparator(std::string &buf);
-void DeterminePaths(const char *exe, bool only_local_path);
+void DeterminePaths(std::string_view exe, bool only_local_path);
 std::unique_ptr<char[]> ReadFileToMem(const std::string &filename, size_t &lenp, size_t maxsize);
 bool FileExists(const std::string &filename);
 bool ExtractTar(const std::string &tar_filename, Subdirectory subdir);
diff --git a/src/fios.cpp b/src/fios.cpp
index 2011e695c2..dbab825654 100644
--- a/src/fios.cpp
+++ b/src/fios.cpp
@@ -12,6 +12,7 @@
 
 #include "stdafx.h"
 #include "3rdparty/md5/md5.h"
+#include "core/string_consumer.hpp"
 #include "fileio_func.h"
 #include "fios.h"
 #include "network/network_content.h"
@@ -108,11 +109,9 @@ const FiosItem *FileList::FindItem(const std::string_view file)
 	}
 
 	/* If no name matches, try to parse it as number */
-	int i;
-	const char *endptr = std::from_chars(file.data(), file.data() + file.size(), i, 10).ptr;
-	if (file.data() == endptr || endptr != file.data() + file.size()) i = -1;
-
-	if (IsInsideMM(i, 0, this->size())) return &this->at(i);
+	StringConsumer consumer{file};
+	auto number = consumer.TryReadIntegerBase<int>(10);
+	if (number.has_value() && !consumer.AnyBytesLeft() && IsInsideMM(*number, 0, this->size())) return &this->at(*number);
 
 	/* As a last effort assume it is an OpenTTD savegame and
 	 * that the ".sav" part was not given. */
@@ -192,21 +191,21 @@ bool FiosBrowseTo(const FiosItem *item)
  * @param ext Filename extension (use \c "" for no extension).
  * @return The completed filename.
  */
-static std::string FiosMakeFilename(const std::string *path, const char *name, const char *ext)
+static std::string FiosMakeFilename(const std::string *path, std::string_view name, std::string_view ext)
 {
-	std::string buf;
+	std::string_view base_path;
 
 	if (path != nullptr) {
-		buf = *path;
+		base_path = *path;
 		/* Remove trailing path separator, if present */
-		if (!buf.empty() && buf.back() == PATHSEPCHAR) buf.pop_back();
+		if (!base_path.empty() && base_path.back() == PATHSEPCHAR) base_path.remove_suffix(1);
 	}
 
 	/* Don't append the extension if it is already there */
-	const char *period = strrchr(name, '.');
-	if (period != nullptr && StrEqualsIgnoreCase(period, ext)) ext = "";
+	auto period = name.find_last_of('.');
+	if (period != std::string_view::npos && StrEqualsIgnoreCase(name.substr(period), ext)) ext = "";
 
-	return buf + PATHSEP + name + ext;
+	return fmt::format("{}{}{}{}", base_path, PATHSEP, name, ext);
 }
 
 /**
@@ -214,9 +213,9 @@ static std::string FiosMakeFilename(const std::string *path, const char *name, c
  * @param name Name of the file.
  * @return The completed filename.
  */
-std::string FiosMakeSavegameName(const char *name)
+std::string FiosMakeSavegameName(std::string_view name)
 {
-	const char *extension = (_game_mode == GM_EDITOR) ? ".scn" : ".sav";
+	std::string_view extension = (_game_mode == GM_EDITOR) ? ".scn" : ".sav";
 
 	return FiosMakeFilename(_fios_path, name, extension);
 }
@@ -226,12 +225,9 @@ std::string FiosMakeSavegameName(const char *name)
  * @param name Filename.
  * @return The completed filename.
  */
-std::string FiosMakeHeightmapName(const char *name)
+std::string FiosMakeHeightmapName(std::string_view name)
 {
-	std::string ext(".");
-	ext += GetCurrentScreenshotExtension();
-
-	return FiosMakeFilename(_fios_path, name, ext.c_str());
+	return FiosMakeFilename(_fios_path, name, fmt::format(".{}", GetCurrentScreenshotExtension()));
 }
 
 /**
@@ -239,7 +235,7 @@ std::string FiosMakeHeightmapName(const char *name)
  * @param name Filename to delete.
  * @return Whether the file deletion was successful.
  */
-bool FiosDelete(const char *name)
+bool FiosDelete(std::string_view name)
 {
 	return FioRemove(FiosMakeSavegameName(name));
 }
@@ -591,13 +587,13 @@ void FiosGetTownDataList(SaveLoadOperation fop, bool show_dirs, FileList &file_l
  * Get the directory for screenshots.
  * @return path to screenshots
  */
-const char *FiosGetScreenshotDir()
+std::string_view FiosGetScreenshotDir()
 {
 	static std::optional<std::string> fios_screenshot_path;
 
 	if (!fios_screenshot_path) fios_screenshot_path = FioFindDirectory(SCREENSHOT_DIR);
 
-	return fios_screenshot_path->c_str();
+	return *fios_screenshot_path;
 }
 
 /** Basic data to distinguish a scenario. Used in the server list window */
diff --git a/src/fios.h b/src/fios.h
index c4a72266a6..d3a388076f 100644
--- a/src/fios.h
+++ b/src/fios.h
@@ -112,9 +112,9 @@ bool FiosBrowseTo(const FiosItem *item);
 
 std::string FiosGetCurrentPath();
 std::optional<uint64_t> FiosGetDiskFreeSpace(const std::string &path);
-bool FiosDelete(const char *name);
-std::string FiosMakeHeightmapName(const char *name);
-std::string FiosMakeSavegameName(const char *name);
+bool FiosDelete(std::string_view name);
+std::string FiosMakeHeightmapName(std::string_view name);
+std::string FiosMakeSavegameName(std::string_view name);
 
 std::tuple<FiosType, std::string> FiosGetSavegameListCallback(SaveLoadOperation fop, const std::string &file, const std::string_view ext);
 std::tuple<FiosType, std::string> FiosGetScenarioListCallback(SaveLoadOperation fop, const std::string &file, const std::string_view ext);
diff --git a/src/os/windows/win32.cpp b/src/os/windows/win32.cpp
index fd04cd57f7..36761d7b0e 100644
--- a/src/os/windows/win32.cpp
+++ b/src/os/windows/win32.cpp
@@ -231,7 +231,7 @@ char *getcwd(char *buf, size_t size)
 
 extern std::string _config_file;
 
-void DetermineBasePaths(const char *exe)
+void DetermineBasePaths(std::string_view exe)
 {
 	extern std::array<std::string, NUM_SEARCHPATHS> _searchpaths;
 
diff --git a/src/screenshot.cpp b/src/screenshot.cpp
index 12c4862859..81ab57c06a 100644
--- a/src/screenshot.cpp
+++ b/src/screenshot.cpp
@@ -132,7 +132,7 @@ static void LargeWorldCallback(Viewport &vp, void *buf, uint y, uint pitch, uint
  * @param crashlog   Create path for crash.png
  * @return Pathname for a screenshot file.
  */
-static const char *MakeScreenshotName(std::string_view default_fn, std::string_view ext, bool crashlog = false)
+static std::string_view MakeScreenshotName(std::string_view default_fn, std::string_view ext, bool crashlog = false)
 {
 	bool generate = _screenshot_name.empty();
 
@@ -154,7 +154,7 @@ static const char *MakeScreenshotName(std::string_view default_fn, std::string_v
 	/* Add extension to screenshot file */
 	_screenshot_name += fmt::format(".{}", ext);
 
-	const char *screenshot_dir = crashlog ? _personal_dir.c_str() : FiosGetScreenshotDir();
+	std::string_view screenshot_dir = crashlog ? _personal_dir : FiosGetScreenshotDir();
 
 	for (uint serial = 1;; serial++) {
 		_full_screenshot_path = fmt::format("{}{}", screenshot_dir, _screenshot_name);
@@ -166,7 +166,7 @@ static const char *MakeScreenshotName(std::string_view default_fn, std::string_v
 		_screenshot_name += fmt::format("#{}.{}", serial, ext);
 	}
 
-	return _full_screenshot_path.c_str();
+	return _full_screenshot_path;
 }
 
 /** Make a screenshot of the current screen. */
@@ -311,7 +311,7 @@ static void HeightmapCallback(void *buffer, uint y, uint, uint n)
  * Make a heightmap of the current map.
  * @param filename Filename to use for saving.
  */
-bool MakeHeightmapScreenshot(const char *filename)
+bool MakeHeightmapScreenshot(std::string_view filename)
 {
 	auto provider = GetScreenshotProvider();
 	if (provider == nullptr) return false;
diff --git a/src/screenshot.h b/src/screenshot.h
index 4c9669cb34..2cbd827b1a 100644
--- a/src/screenshot.h
+++ b/src/screenshot.h
@@ -23,7 +23,7 @@ enum ScreenshotType : uint8_t {
 	SC_MINIMAP,     ///< Minimap screenshot.
 };
 
-bool MakeHeightmapScreenshot(const char *filename);
+bool MakeHeightmapScreenshot(std::string_view filename);
 void MakeScreenshotWithConfirm(ScreenshotType t);
 bool MakeScreenshot(ScreenshotType t, const std::string &name, uint32_t width = 0, uint32_t height = 0);
 bool MakeMinimapWorldScreenshot();
diff --git a/src/screenshot_bmp.cpp b/src/screenshot_bmp.cpp
index 37d23c9439..4d71d71253 100644
--- a/src/screenshot_bmp.cpp
+++ b/src/screenshot_bmp.cpp
@@ -43,7 +43,7 @@ class ScreenshotProvider_Bmp : public ScreenshotProvider {
 public:
 	ScreenshotProvider_Bmp() : ScreenshotProvider("bmp", "BMP", 10) {}
 
-	bool MakeImage(const char *name, const ScreenshotCallback &callb, uint w, uint h, int pixelformat, const Colour *palette) override
+	bool MakeImage(std::string_view name, const ScreenshotCallback &callb, uint w, uint h, int pixelformat, const Colour *palette) override
 	{
 		uint bpp; // bytes per pixel
 		switch (pixelformat) {
diff --git a/src/screenshot_pcx.cpp b/src/screenshot_pcx.cpp
index 6359b25751..8c9f1dd006 100644
--- a/src/screenshot_pcx.cpp
+++ b/src/screenshot_pcx.cpp
@@ -41,7 +41,7 @@ class ScreenshotProvider_Pcx : public ScreenshotProvider {
 public:
 	ScreenshotProvider_Pcx() : ScreenshotProvider("pcx", "PCX", 20) {}
 
-	bool MakeImage(const char *name, const ScreenshotCallback &callb, uint w, uint h, int pixelformat, const Colour *palette) override
+	bool MakeImage(std::string_view name, const ScreenshotCallback &callb, uint w, uint h, int pixelformat, const Colour *palette) override
 	{
 		uint maxlines;
 		uint y;
diff --git a/src/screenshot_png.cpp b/src/screenshot_png.cpp
index ee2220c4be..c3da01499e 100644
--- a/src/screenshot_png.cpp
+++ b/src/screenshot_png.cpp
@@ -30,7 +30,7 @@ class ScreenshotProvider_Png : public ScreenshotProvider {
 public:
 	ScreenshotProvider_Png() : ScreenshotProvider("png", "PNG", 0) {}
 
-	bool MakeImage(const char *name, const ScreenshotCallback &callb, uint w, uint h, int pixelformat, const Colour *palette) override
+	bool MakeImage(std::string_view name, const ScreenshotCallback &callb, uint w, uint h, int pixelformat, const Colour *palette) override
 	{
 		png_color rq[256];
 		uint i, y, n;
@@ -46,7 +46,7 @@ public:
 		if (!of.has_value()) return false;
 		auto &f = *of;
 
-		png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, const_cast<char *>(name), png_my_error, png_my_warning);
+		png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, &name, png_my_error, png_my_warning);
 
 		if (png_ptr == nullptr) {
 			return false;
@@ -169,13 +169,13 @@ public:
 private:
 	static void PNGAPI png_my_error(png_structp png_ptr, png_const_charp message)
 	{
-		Debug(misc, 0, "[libpng] error: {} - {}", message, (const char *)png_get_error_ptr(png_ptr));
+		Debug(misc, 0, "[libpng] error: {} - {}", message, *static_cast<std::string_view *>(png_get_error_ptr(png_ptr)));
 		longjmp(png_jmpbuf(png_ptr), 1);
 	}
 
 	static void PNGAPI png_my_warning(png_structp png_ptr, png_const_charp message)
 	{
-		Debug(misc, 1, "[libpng] warning: {} - {}", message, (const char *)png_get_error_ptr(png_ptr));
+		Debug(misc, 1, "[libpng] warning: {} - {}", message, *static_cast<std::string_view *>(png_get_error_ptr(png_ptr)));
 	}
 };
 
diff --git a/src/screenshot_type.h b/src/screenshot_type.h
index 0be00c7d96..d93f7c20bb 100644
--- a/src/screenshot_type.h
+++ b/src/screenshot_type.h
@@ -36,7 +36,7 @@ public:
 		ProviderManager<ScreenshotProvider>::Unregister(*this);
 	}
 
-	virtual bool MakeImage(const char *name, const ScreenshotCallback &callb, uint w, uint h, int pixelformat, const Colour *palette) = 0;
+	virtual bool MakeImage(std::string_view name, const ScreenshotCallback &callb, uint w, uint h, int pixelformat, const Colour *palette) = 0;
 };
 
 #endif /* SCREENSHOT_TYPE_H */