diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7567dd0..8f6589b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -424,6 +424,8 @@ target_include_directories(rhubarb-tools PUBLIC "src/tools")
 target_link_libraries(rhubarb-tools
 	cppFormat
 	whereami
+	utfcpp
+	utf8proc
 )
 
 # Define Rhubarb executable
diff --git a/src/lib/rhubarbLib.cpp b/src/lib/rhubarbLib.cpp
index c643d15..29c25bc 100644
--- a/src/lib/rhubarbLib.cpp
+++ b/src/lib/rhubarbLib.cpp
@@ -6,13 +6,13 @@
 #include "WaveFileReader.h"
 
 using boost::optional;
-using std::u32string;
+using std::string;
 using boost::filesystem::path;
 using std::unique_ptr;
 
 JoiningContinuousTimeline<Shape> animateAudioClip(
 	const AudioClip& audioClip,
-	optional<u32string> dialog,
+	optional<string> dialog,
 	const ShapeSet& targetShapeSet,
 	int maxThreadCount,
 	ProgressSink& progressSink)
@@ -32,7 +32,7 @@ unique_ptr<AudioClip> createWaveAudioClip(path filePath) {
 
 JoiningContinuousTimeline<Shape> animateWaveFile(
 	path filePath,
-	optional<u32string> dialog,
+	optional<string> dialog,
 	const ShapeSet& targetShapeSet,
 	int maxThreadCount,
 	ProgressSink& progressSink)
diff --git a/src/lib/rhubarbLib.h b/src/lib/rhubarbLib.h
index a8d588f..b4457c9 100644
--- a/src/lib/rhubarbLib.h
+++ b/src/lib/rhubarbLib.h
@@ -9,14 +9,14 @@
 
 JoiningContinuousTimeline<Shape> animateAudioClip(
 	const AudioClip& audioClip,
-	boost::optional<std::u32string> dialog,
+	boost::optional<std::string> dialog,
 	const ShapeSet& targetShapeSet,
 	int maxThreadCount,
 	ProgressSink& progressSink);
 
 JoiningContinuousTimeline<Shape> animateWaveFile(
 	boost::filesystem::path filePath,
-	boost::optional<std::u32string> dialog,
+	boost::optional<std::string> dialog,
 	const ShapeSet& targetShapeSet,
 	int maxThreadCount,
 	ProgressSink& progressSink);
diff --git a/src/main.cpp b/src/main.cpp
index 860502b..e709181 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -24,10 +24,11 @@
 #include <boost/iostreams/device/null.hpp>
 #include "targetShapeSet.h"
 #include <boost/utility/in_place_factory.hpp>
+#include "platformTools.h"
 
 using std::exception;
 using std::string;
-using std::u32string;
+using std::string;
 using std::vector;
 using std::unique_ptr;
 using std::make_unique;
@@ -97,7 +98,14 @@ ShapeSet getTargetShapeSet(const string& extendedShapesString) {
 	return result;
 }
 
-int main(int argc, char *argv[]) {
+int main(int platformArgc, char *platformArgv[]) {
+	// Use UTF-8 throughout
+	useUtf8ForConsole();
+	useUtf8ForBoostFilesystem();
+
+	// Convert command-line arguments to UTF-8
+	const vector<string> args = argsToUtf8(platformArgc, platformArgv);
+
 	auto pausableStderrSink = addPausableStdErrSink(logging::Level::Warn);
 	pausableStderrSink->pause();
 
@@ -130,7 +138,11 @@ int main(int argc, char *argv[]) {
 		});
 
 		// Parse command line
-		cmd.parse(argc, argv);
+		{
+			// TCLAP mutates the function argument! Pass a copy.
+			vector<string> argsCopy(args);
+			cmd.parse(argsCopy);
+		}
 		if (quietMode.getValue()) {
 			infoStream = &nullStream;
 		}
@@ -146,7 +158,7 @@ int main(int argc, char *argv[]) {
 		}
 
 		logging::infoFormat("Application startup. Command line: {}", join(
-			vector<char*>(argv, argv + argc) | transformed([](char* arg) { return fmt::format("\"{}\"", arg); }), " "));
+			args | transformed([](string arg) { return fmt::format("\"{}\"", arg); }), " "));
 
 		try {
 			*infoStream << fmt::format("Generating lip sync data for {}.", inputFilePath) << std::endl;
@@ -158,7 +170,7 @@ int main(int argc, char *argv[]) {
 				// Animate the recording
 				animation = animateWaveFile(
 					inputFilePath,
-					dialogFile.isSet() ? readUtf8File(path(dialogFile.getValue())) : boost::optional<u32string>(),
+					dialogFile.isSet() ? readUtf8File(path(dialogFile.getValue())) : boost::optional<string>(),
 					targetShapeSet,
 					maxThreadCount.getValue(),
 					progressBar);
diff --git a/src/recognition/languageModels.cpp b/src/recognition/languageModels.cpp
index 093c2e6..c7b4a2c 100644
--- a/src/recognition/languageModels.cpp
+++ b/src/recognition/languageModels.cpp
@@ -11,7 +11,6 @@
 #include <gsl_util.h>
 
 using std::string;
-using std::u32string;
 using std::vector;
 using std::regex;
 using std::map;
diff --git a/src/recognition/phoneRecognition.cpp b/src/recognition/phoneRecognition.cpp
index fc07170..f56201f 100644
--- a/src/recognition/phoneRecognition.cpp
+++ b/src/recognition/phoneRecognition.cpp
@@ -44,7 +44,7 @@ using std::regex;
 using std::regex_replace;
 using std::chrono::duration;
 using boost::optional;
-using std::u32string;
+using std::string;
 using std::chrono::duration_cast;
 using std::array;
 
@@ -251,7 +251,7 @@ lambda_unique_ptr<ngram_model_t> createDefaultLanguageModel(ps_decoder_t& decode
 	return std::move(result);
 }
 
-lambda_unique_ptr<ngram_model_t> createDialogLanguageModel(ps_decoder_t& decoder, const u32string& dialog) {
+lambda_unique_ptr<ngram_model_t> createDialogLanguageModel(ps_decoder_t& decoder, const string& dialog) {
 	// Split dialog into normalized words
 	vector<string> words = tokenizeText(dialog, [&](const string& word) { return dictionaryContains(*decoder.dict, word); });
 
@@ -264,7 +264,7 @@ lambda_unique_ptr<ngram_model_t> createDialogLanguageModel(ps_decoder_t& decoder
 	return createLanguageModel(words, decoder);
 }
 
-lambda_unique_ptr<ngram_model_t> createBiasedLanguageModel(ps_decoder_t& decoder, const u32string& dialog) {
+lambda_unique_ptr<ngram_model_t> createBiasedLanguageModel(ps_decoder_t& decoder, const string& dialog) {
 	auto defaultLanguageModel = createDefaultLanguageModel(decoder);
 	auto dialogLanguageModel = createDialogLanguageModel(decoder, dialog);
 	constexpr int modelCount = 2;
@@ -281,7 +281,7 @@ lambda_unique_ptr<ngram_model_t> createBiasedLanguageModel(ps_decoder_t& decoder
 	return std::move(result);
 }
 
-lambda_unique_ptr<ps_decoder_t> createDecoder(optional<u32string> dialog) {
+lambda_unique_ptr<ps_decoder_t> createDecoder(optional<string> dialog) {
 	lambda_unique_ptr<cmd_ln_t> config(
 		cmd_ln_init(
 			nullptr, ps_args(), true,
@@ -435,7 +435,7 @@ Timeline<Phone> utteranceToPhones(
 
 BoundedTimeline<Phone> recognizePhones(
 	const AudioClip& inputAudioClip,
-	optional<u32string> dialog,
+	optional<string> dialog,
 	int maxThreadCount,
 	ProgressSink& progressSink)
 {
diff --git a/src/recognition/phoneRecognition.h b/src/recognition/phoneRecognition.h
index 8deb5d8..61e94ee 100644
--- a/src/recognition/phoneRecognition.h
+++ b/src/recognition/phoneRecognition.h
@@ -7,6 +7,6 @@
 
 BoundedTimeline<Phone> recognizePhones(
 	const AudioClip& audioClip,
-	boost::optional<std::u32string> dialog,
+	boost::optional<std::string> dialog,
 	int maxThreadCount,
 	ProgressSink& progressSink);
diff --git a/src/recognition/tokenization.cpp b/src/recognition/tokenization.cpp
index e2b9000..2fb7741 100644
--- a/src/recognition/tokenization.cpp
+++ b/src/recognition/tokenization.cpp
@@ -10,7 +10,6 @@ extern "C" {
 }
 
 using std::runtime_error;
-using std::u32string;
 using std::string;
 using std::vector;
 using std::regex;
@@ -34,9 +33,12 @@ static const cst_synth_module synth_method_normalize[] = {
 };
 
 vector<string> tokenizeViaFlite(const string& text) {
+	// Convert text to ASCII
+	const string asciiText = utf8ToAscii(text);
+
 	// Create utterance object with text
 	lambda_unique_ptr<cst_utterance> utterance(new_utterance(), [](cst_utterance* utterance) { delete_utterance(utterance); });
-	utt_set_input_text(utterance.get(), text.c_str());
+	utt_set_input_text(utterance.get(), asciiText.c_str());
 	lambda_unique_ptr<cst_voice> voice = createDummyVoice();
 	utt_init(utterance.get(), voice.get());
 
@@ -73,8 +75,8 @@ optional<string> findSimilarDictionaryWord(const string& word, function<bool(con
 	return boost::none;
 }
 
-vector<string> tokenizeText(const u32string& text, function<bool(const string&)> dictionaryContains) {
-	vector<string> words = tokenizeViaFlite(toAscii(text));
+vector<string> tokenizeText(const string& text, function<bool(const string&)> dictionaryContains) {
+	vector<string> words = tokenizeViaFlite(text);
 
 	// Join words separated by apostophes
 	for (int i = words.size() - 1; i > 0; --i) {
diff --git a/src/recognition/tokenization.h b/src/recognition/tokenization.h
index 16e48fc..c990501 100644
--- a/src/recognition/tokenization.h
+++ b/src/recognition/tokenization.h
@@ -4,4 +4,4 @@
 #include <functional>
 #include <string>
 
-std::vector<std::string> tokenizeText(const std::u32string& text, std::function<bool(const std::string&)> dictionaryContains);
+std::vector<std::string> tokenizeText(const std::string& text, std::function<bool(const std::string&)> dictionaryContains);
diff --git a/src/tools/asciiCases.cpp b/src/tools/asciiCases.cpp
deleted file mode 100644
index d7cc2ff..0000000
--- a/src/tools/asciiCases.cpp
+++ /dev/null
@@ -1,94 +0,0 @@
-// Generated by asciiCases.rb; don't modify by hand!
-
-case U'À': case U'Á': case U'Â': case U'Ã': case U'Ä': case U'Å': case U'Ā': case U'Ă': case U'Ą': case U'Ǎ': case U'Ǟ': case U'Ǡ': case U'Ǻ': case U'Ȁ': case U'Ȃ': case U'Ȧ': case U'Ⱥ':
-	return 'A';
-case U'Ɓ': case U'Ƃ': case U'Ƀ':
-	return 'B';
-case U'Ç': case U'Ć': case U'Ĉ': case U'Ċ': case U'Č': case U'Ƈ': case U'Ȼ':
-	return 'C';
-case U'Ď': case U'Đ': case U'Ɗ': case U'Ƌ':
-	return 'D';
-case U'È': case U'É': case U'Ê': case U'Ë': case U'Ē': case U'Ĕ': case U'Ė': case U'Ę': case U'Ě': case U'Ȅ': case U'Ȇ': case U'Ȩ': case U'Ɇ':
-	return 'E';
-case U'Ƒ':
-	return 'F';
-case U'Ĝ': case U'Ğ': case U'Ġ': case U'Ģ': case U'Ɠ': case U'Ǥ': case U'Ǧ': case U'Ǵ':
-	return 'G';
-case U'Ĥ': case U'Ħ': case U'Ȟ':
-	return 'H';
-case U'Ì': case U'Í': case U'Î': case U'Ï': case U'Ĩ': case U'Ī': case U'Ĭ': case U'Į': case U'İ': case U'Ɨ': case U'Ǐ': case U'Ȉ': case U'Ȋ':
-	return 'I';
-case U'Ĵ': case U'Ɉ':
-	return 'J';
-case U'Ķ': case U'Ƙ': case U'Ǩ':
-	return 'K';
-case U'Ĺ': case U'Ļ': case U'Ľ': case U'Ŀ': case U'Ł': case U'Ƚ':
-	return 'L';
-case U'Ñ': case U'Ń': case U'Ņ': case U'Ň': case U'Ɲ': case U'Ǹ': case U'Ƞ':
-	return 'N';
-case U'Ò': case U'Ó': case U'Ô': case U'Õ': case U'Ö': case U'Ø': case U'Ō': case U'Ŏ': case U'Ő': case U'Ɵ': case U'Ơ': case U'Ǒ': case U'Ǫ': case U'Ǭ': case U'Ǿ': case U'Ȍ': case U'Ȏ': case U'Ȫ': case U'Ȭ': case U'Ȯ': case U'Ȱ':
-	return 'O';
-case U'Ƥ':
-	return 'P';
-case U'Ŕ': case U'Ŗ': case U'Ř': case U'Ȑ': case U'Ȓ': case U'Ɍ':
-	return 'R';
-case U'Ś': case U'Ŝ': case U'Ş': case U'Š': case U'Ș':
-	return 'S';
-case U'Ţ': case U'Ť': case U'Ŧ': case U'Ƭ': case U'Ʈ': case U'Ț': case U'Ⱦ':
-	return 'T';
-case U'Ù': case U'Ú': case U'Û': case U'Ü': case U'Ũ': case U'Ū': case U'Ŭ': case U'Ů': case U'Ű': case U'Ų': case U'Ư': case U'Ǔ': case U'Ǖ': case U'Ǘ': case U'Ǚ': case U'Ǜ': case U'Ȕ': case U'Ȗ': case U'Ʉ':
-	return 'U';
-case U'Ʋ':
-	return 'V';
-case U'Ŵ':
-	return 'W';
-case U'Ý': case U'Ŷ': case U'Ÿ': case U'Ƴ': case U'Ȳ': case U'Ɏ':
-	return 'Y';
-case U'Ź': case U'Ż': case U'Ž': case U'Ƶ': case U'Ȥ':
-	return 'Z';
-case U'à': case U'á': case U'â': case U'ã': case U'ä': case U'å': case U'ā': case U'ă': case U'ą': case U'ǎ': case U'ǟ': case U'ǡ': case U'ǻ': case U'ȁ': case U'ȃ': case U'ȧ':
-	return 'a';
-case U'ƀ': case U'ƃ':
-	return 'b';
-case U'ç': case U'ć': case U'ĉ': case U'ċ': case U'č': case U'ƈ': case U'ȼ':
-	return 'c';
-case U'ď': case U'đ': case U'ƌ': case U'ȡ':
-	return 'd';
-case U'è': case U'é': case U'ê': case U'ë': case U'ē': case U'ĕ': case U'ė': case U'ę': case U'ě': case U'ȅ': case U'ȇ': case U'ȩ': case U'ɇ':
-	return 'e';
-case U'ƒ':
-	return 'f';
-case U'ĝ': case U'ğ': case U'ġ': case U'ģ': case U'ǥ': case U'ǧ': case U'ǵ':
-	return 'g';
-case U'ĥ': case U'ħ': case U'ȟ':
-	return 'h';
-case U'ì': case U'í': case U'î': case U'ï': case U'ĩ': case U'ī': case U'ĭ': case U'į': case U'ǐ': case U'ȉ': case U'ȋ':
-	return 'i';
-case U'ĵ': case U'ǰ': case U'ɉ':
-	return 'j';
-case U'ķ': case U'ƙ': case U'ǩ':
-	return 'k';
-case U'ĺ': case U'ļ': case U'ľ': case U'ŀ': case U'ł': case U'ƚ': case U'ȴ':
-	return 'l';
-case U'ñ': case U'ń': case U'ņ': case U'ň': case U'ʼn': case U'ƞ': case U'ǹ': case U'ȵ':
-	return 'n';
-case U'ò': case U'ó': case U'ô': case U'õ': case U'ö': case U'ø': case U'ō': case U'ŏ': case U'ő': case U'ơ': case U'ǒ': case U'ǫ': case U'ǭ': case U'ǿ': case U'ȍ': case U'ȏ': case U'ȫ': case U'ȭ': case U'ȯ': case U'ȱ':
-	return 'o';
-case U'ƥ':
-	return 'p';
-case U'ɋ':
-	return 'q';
-case U'ŕ': case U'ŗ': case U'ř': case U'ȑ': case U'ȓ': case U'ɍ':
-	return 'r';
-case U'ś': case U'ŝ': case U'ş': case U'š': case U'ș': case U'ȿ':
-	return 's';
-case U'ţ': case U'ť': case U'ŧ': case U'ƫ': case U'ƭ': case U'ț': case U'ȶ':
-	return 't';
-case U'ù': case U'ú': case U'û': case U'ü': case U'ũ': case U'ū': case U'ŭ': case U'ů': case U'ű': case U'ų': case U'ư': case U'ǔ': case U'ǖ': case U'ǘ': case U'ǚ': case U'ǜ': case U'ȕ': case U'ȗ':
-	return 'u';
-case U'ŵ':
-	return 'w';
-case U'ý': case U'ÿ': case U'ŷ': case U'ƴ': case U'ȳ': case U'ɏ':
-	return 'y';
-case U'ź': case U'ż': case U'ž': case U'ƶ': case U'ȥ': case U'ɀ':
-	return 'z';
diff --git a/src/tools/asciiCases.rb b/src/tools/asciiCases.rb
deleted file mode 100644
index ef584e3..0000000
--- a/src/tools/asciiCases.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require 'open-uri'
-require 'csv'
-
-# Create mapping from ASCII characters to related Unicode characters
-mapping = Hash.new{ |hash, key| hash[key] = [] }
-url = 'http://www.unicode.org/Public/8.0.0/ucd/UnicodeData.txt'
-headers = [:code, :name, :category]
-CSV.new(open(url), :col_sep => ';', :headers => headers).each do |row|
-  code = row[:code].hex
-  next if code < 0x80
-  break if code > 0x24f
-  
-  char = [code].pack('U')
-  name = row[:name]
-  match = /^LATIN (CAPITAL|SMALL) LETTER ([A-Z])\b(?!.*\bLETTER\b)/.match(name)
-  if match
-    baseChar = match[2]
-    if match[1] == 'SMALL'
-      baseChar = (baseChar.ord + 0x20).chr
-    end
-    mapping[baseChar] << char
-  end
-end
-mapping = mapping.sort.to_h
-
-# Generate asciiCases.cpp
-File.open('asciiCases.cpp', 'w') do |file|
-  file.print "// Generated by #{__FILE__}; don't modify by hand!\n\n"
-  mapping.each do |asciiChar, unicodeChars|
-    file.print unicodeChars.map { |c| "case U'#{c}':" }.join(' '), "\n"
-    file.print "\treturn '#{asciiChar}';\n"
-  end
-end
diff --git a/src/tools/platformTools.cpp b/src/tools/platformTools.cpp
index 2fcc9fe..116ff97 100644
--- a/src/tools/platformTools.cpp
+++ b/src/tools/platformTools.cpp
@@ -6,9 +6,21 @@
 #include <boost/uuid/uuid_io.hpp>
 #include "platformTools.h"
 #include <whereami.h>
+#include <utf8.h>
+#include <gsl_util.h>
+#include "tools.h"
+#include <boost/filesystem/detail/utf8_codecvt_facet.hpp> 
+#include <iostream>
+
+#ifdef _WIN32
+	#include <Windows.h>
+	#include <io.h>
+	#include <fcntl.h>
+#endif
 
 using boost::filesystem::path;
 using std::string;
+using std::vector;
 
 path getBinPath() {
 	static const path binPath = [] {
@@ -69,3 +81,73 @@ std::string errorNumberToString(int errorNumber) {
 #endif
 	return message;
 }
+
+vector<string> argsToUtf8(int argc, char* argv[]) {
+#ifdef _WIN32
+	// On Windows, there is no way to convert the single-byte argument strings to Unicode.
+	// We'll just ignore them.
+	UNUSED(argc);
+	UNUSED(argv);
+
+	// Get command-line arguments as UTF16 strings
+	int argumentCount;
+	static_assert(sizeof(wchar_t) == sizeof(char16_t), "Expected wchar_t to be a 16-bit type.");
+	char16_t** args = reinterpret_cast<char16_t**>(CommandLineToArgvW(GetCommandLineW(), &argumentCount));
+	if (!args) {
+		throw std::runtime_error("Error splitting the UTF-16 command line arguments.");
+	}
+	auto freeArgs = gsl::finally([&]() { LocalFree(args); });
+	assert(argumentCount == argc);
+
+	// Convert UTF16 strings to UTF8
+	vector<string> result;
+	for (int i = 0; i < argc; ++i) {
+		std::u16string utf16String(args[i]);
+		string utf8String;
+		utf8::utf16to8(utf16String.begin(), utf16String.end(), back_inserter(utf8String));
+		result.push_back(utf8String);
+	}
+	return result;
+#else
+	// On Unix systems, command-line args are already in UTF-8 format. Just convert them to strings.
+	vector<string> result;
+	for (int i = 0; i < argc; ++i) {
+		result.push_back(string(argv[i]));
+	}
+	return result;
+#endif
+}
+
+class ConsoleBuffer : public std::stringbuf {
+public:
+	explicit ConsoleBuffer(FILE* file)
+		: file(file) {}
+
+	int sync() override {
+		fputs(str().c_str(), file);
+		str("");
+		return 0;
+	}
+
+private:
+	FILE* file;
+};
+
+void useUtf8ForConsole() {
+// Unix systems already expect UTF-8-encoded data
+#ifdef _WIN32
+	// Set console code page to UTF-8 so the console knows how to interpret string data
+	SetConsoleOutputCP(CP_UTF8);
+
+	// Prevent default stream buffer from chopping up UTF-8 byte sequences.
+	// See https://stackoverflow.com/questions/45575863/how-to-print-utf-8-strings-to-stdcout-on-windows
+	std::cout.rdbuf(new ConsoleBuffer(stdout));
+	std::cerr.rdbuf(new ConsoleBuffer(stderr));
+#endif
+}
+
+void useUtf8ForBoostFilesystem() {
+	std::locale globalLocale = std::locale();
+	std::locale utf8Locale(globalLocale, new boost::filesystem::detail::utf8_codecvt_facet);
+	path::imbue(utf8Locale);
+}
diff --git a/src/tools/platformTools.h b/src/tools/platformTools.h
index d5b3529..2fec1db 100644
--- a/src/tools/platformTools.h
+++ b/src/tools/platformTools.h
@@ -10,3 +10,8 @@ boost::filesystem::path getTempFilePath();
 
 std::tm getLocalTime(const time_t& time);
 std::string errorNumberToString(int errorNumber);
+
+std::vector<std::string> argsToUtf8(int argc, char *argv[]);
+
+void useUtf8ForConsole();
+void useUtf8ForBoostFilesystem();
\ No newline at end of file
diff --git a/src/tools/stringTools.cpp b/src/tools/stringTools.cpp
index ab0b9e6..5d27bbe 100644
--- a/src/tools/stringTools.cpp
+++ b/src/tools/stringTools.cpp
@@ -1,12 +1,16 @@
-#include "stringTools.h"
+#include "stringTools.h"
 #include <boost/algorithm/string/trim.hpp>
-#include <codecvt>
+#include <utf8.h>
+#include <utf8proc.h>
+#include <regex>
 
 using std::string;
 using std::wstring;
 using std::u32string;
 using std::vector;
 using boost::optional;
+using std::regex;
+using std::regex_replace;
 
 vector<string> splitIntoLines(const string& s) {
 	vector<string> lines;
@@ -83,6 +87,10 @@ vector<string> wrapString(const string& s, int lineLength, int hangingIndent) {
 	return lines;
 }
 
+bool isValidUtf8(const string& s) {
+	return utf8::is_valid(s.begin(), s.end());
+}
+
 wstring latin1ToWide(const string& s) {
 	wstring result;
 	for (unsigned char c : s) {
@@ -91,40 +99,61 @@ wstring latin1ToWide(const string& s) {
 	return result;
 }
 
-optional<char> toAscii(char32_t ch) {
-	switch (ch) {
-#include "asciiCases.cpp"
-	default:
-		return ch < 0x80 ? static_cast<char>(ch) : optional<char>();
-	}
-}
+string utf8ToAscii(const string s) {
+	// Normalize string, simplifying it as much as possible
+	const NormalizationOptions options = NormalizationOptions::CompatibilityMode
+		| NormalizationOptions::Decompose
+		| NormalizationOptions::SimplifyLineBreaks
+		| NormalizationOptions::SimplifyWhiteSpace
+		| NormalizationOptions::StripCharacterMarkings
+		| NormalizationOptions::StripIgnorableCharacters;
+	string simplified = normalizeUnicode(s, options);
 
-string toAscii(const u32string& s) {
-	string result;
-	for (char32_t ch : s) {
-		optional<char> ascii = toAscii(ch);
-		if (ascii) result.append(1, *ascii);
+	// Replace common Unicode characters with ASCII equivalents
+	static const vector<std::pair<regex, string>> replacements{
+		{regex("«|»|“|”|„|‟"), "\""},
+		{regex("‘|’|‚|‛|‹|›"), "'"},
+		{regex("‐|‑|‒|⁃|⁻|₋|−|➖|–|—|―|﹘|﹣|－"), "-"},
+		{regex("…|⋯"), "..."},
+		{regex("•"), "*"},
+		{regex("†|＋"), "+"},
+		{regex("⁄|∕|⧸|／|/"), "/"},
+		{regex("×"), "x"},
+	};
+	for (const auto& replacement : replacements) {
+		simplified = regex_replace(simplified, replacement.first, replacement.second);
 	}
+
+	// Skip all non-ASCII code points, including multi-byte characters
+	string result;
+	for (char c : simplified) {
+		const bool isAscii = (c & 0x80) == 0;
+		if (isAscii) {
+			result.append(1, c);
+		}
+	}
+
 	return result;
 }
 
-string toAscii(const wstring& s) {
-	string result;
-	for (wchar_t ch : s) {
-		optional<char> ascii = toAscii(ch);
-		if (ascii) result.append(1, *ascii);
-	}
-	return result;
-}
+string normalizeUnicode(const string s, NormalizationOptions options) {
+	char* result;
+	const utf8proc_ssize_t charCount = utf8proc_map(
+		reinterpret_cast<const uint8_t*>(s.data()),
+		s.length(),
+		reinterpret_cast<uint8_t**>(&result),
+		static_cast<utf8proc_option_t>(options));
 
-u32string utf8ToUtf32(const string& s) {
-#if defined(_MSC_VER) && _MSC_VER <= 1900
-	// Workaround for Visual Studio 2015
-	// See https://connect.microsoft.com/VisualStudio/feedback/details/1403302/unresolved-external-when-using-codecvt-utf8
-	std::wstring_convert<std::codecvt_utf8<uint32_t>, uint32_t> convert;
-	return u32string(reinterpret_cast<const char32_t*>(convert.from_bytes(s).c_str()));
-#else
-	std::wstring_convert<std::codecvt_utf8<char32_t>, char32_t> convert;
-	return convert.from_bytes(s);
-#endif
+	if (charCount < 0) {
+		const utf8proc_ssize_t errorCode = charCount;
+		const string message = string("Error normalizing string: ") + utf8proc_errmsg(errorCode);
+		if (errorCode == UTF8PROC_ERROR_INVALIDOPTS) {
+			throw std::invalid_argument(message);
+		}
+		throw std::runtime_error(message);
+	}
+
+	string resultString(result, charCount);
+	free(result);
+	return resultString;
 }
diff --git a/src/tools/stringTools.h b/src/tools/stringTools.h
index bab3854..2964de1 100644
--- a/src/tools/stringTools.h
+++ b/src/tools/stringTools.h
@@ -3,6 +3,7 @@
 #include <vector>
 #include <boost/optional.hpp>
 #include <boost/lexical_cast.hpp>
+#include <utf8proc.h>
 
 std::vector<std::string> splitIntoLines(const std::string& s);
 
@@ -10,15 +11,31 @@ std::vector<std::string> wrapSingleLineString(const std::string& s, int lineLeng
 
 std::vector<std::string> wrapString(const std::string& s, int lineLength, int hangingIndent = 0);
 
+bool isValidUtf8(const std::string& s);
+
 std::wstring latin1ToWide(const std::string& s);
 
 boost::optional<char> toAscii(char32_t ch);
 
-std::string toAscii(const std::u32string& s);
+std::string utf8ToAscii(const std::string s);
 
-std::string toAscii(const std::wstring& s);
+enum class NormalizationOptions : int {
+	CompatibilityMode = UTF8PROC_COMPAT,
+	Compose = UTF8PROC_COMPOSE,
+	Decompose = UTF8PROC_DECOMPOSE,
+	StripIgnorableCharacters = UTF8PROC_IGNORE,
+	ThrowOnUnassignedCodepoints = UTF8PROC_REJECTNA,
+	SimplifyLineBreaks = UTF8PROC_NLF2LS,
+	SimplifyWhiteSpace = UTF8PROC_STRIPCC,
+	StripCharacterMarkings = UTF8PROC_STRIPMARK
+};
 
-std::u32string utf8ToUtf32(const std::string& s);
+constexpr NormalizationOptions
+operator|(NormalizationOptions a, NormalizationOptions b) {
+	return static_cast<NormalizationOptions>(static_cast<int>(a) | static_cast<int>(b));
+}
+
+std::string normalizeUnicode(const std::string s, NormalizationOptions options);
 
 template<typename T>
 std::string join(T range, const std::string separator) {
diff --git a/src/tools/textFiles.cpp b/src/tools/textFiles.cpp
index fd0ac6f..d266f65 100644
--- a/src/tools/textFiles.cpp
+++ b/src/tools/textFiles.cpp
@@ -5,10 +5,9 @@
 #include "stringTools.h"
 
 using std::string;
-using std::u32string;
 using boost::filesystem::path;
 
-u32string readUtf8File(path filePath) {
+string readUtf8File(path filePath) {
 	if (!exists(filePath)) {
 		throw std::invalid_argument(fmt::format("File {} does not exist.", filePath));
 	}
@@ -16,12 +15,12 @@ u32string readUtf8File(path filePath) {
 		boost::filesystem::ifstream file;
 		file.exceptions(std::ifstream::failbit | std::ifstream::badbit);
 		file.open(filePath);
-		string utf8Text((std::istreambuf_iterator<char>(file)), std::istreambuf_iterator<char>());
-		try {
-			return utf8ToUtf32(utf8Text);
-		} catch (...) {
-			std::throw_with_nested(std::runtime_error(fmt::format("File encoding is not ASCII or UTF-8.", filePath)));
+		string text((std::istreambuf_iterator<char>(file)), std::istreambuf_iterator<char>());
+		if (!isValidUtf8(text)) {
+			throw std::runtime_error("File encoding is not ASCII or UTF-8.");
 		}
+
+		return text;
 	} catch (...) {
 		std::throw_with_nested(std::runtime_error(fmt::format("Error reading file {0}.", filePath)));
 	}
diff --git a/src/tools/textFiles.h b/src/tools/textFiles.h
index 3c72a6c..adfe96b 100644
--- a/src/tools/textFiles.h
+++ b/src/tools/textFiles.h
@@ -2,4 +2,4 @@
 
 #include <boost/filesystem/path.hpp>
 
-std::u32string readUtf8File(boost::filesystem::path filePath);
\ No newline at end of file
+std::string readUtf8File(boost::filesystem::path filePath);
\ No newline at end of file
diff --git a/tests/stringToolsTests.cpp b/tests/stringToolsTests.cpp
index 3ecbd92..7f58971 100644
--- a/tests/stringToolsTests.cpp
+++ b/tests/stringToolsTests.cpp
@@ -81,11 +81,15 @@ TEST(latin1ToWide, basic) {
 	EXPECT_EQ(pangramWide, latin1ToWide(pangramLatin1));
 }
 
-// toAscii
+// utf8ToAscii
 
-TEST(toAscii, string) {
+TEST(utf8ToAscii, string) {
 	EXPECT_EQ(
 		"A naive man called  was having pina colada and creme brulee.",
-		toAscii(U"A naïve man called 晨 was having piña colada and crème brûlée."));
-	EXPECT_EQ(string(""), toAscii(U""));
+		utf8ToAscii("A naïve man called 晨 was having piña colada and crème brûlée."));
+	EXPECT_EQ(string(""), utf8ToAscii(""));
+	EXPECT_EQ(string("- - - - - - - - - -"), utf8ToAscii("- ‐ ‑ ‒ – — ― ﹘ ﹣ －"));
+	EXPECT_EQ(string("' ' ' ' \" \" \" \" \" \""), utf8ToAscii("‘ ’ ‚ ‛ “ ” „ ‟ « »"));
+	EXPECT_EQ(string("1 2 3"), utf8ToAscii("¹ ² ³"));
+	EXPECT_EQ(string("1/4 1/2 3/4"), utf8ToAscii("¼ ½ ¾"));
 }
diff --git a/tests/tokenizationTests.cpp b/tests/tokenizationTests.cpp
index dcd3941..577c6bb 100644
--- a/tests/tokenizationTests.cpp
+++ b/tests/tokenizationTests.cpp
@@ -2,6 +2,7 @@
 #include "tokenization.h"
 #include <regex>
 #include <unordered_set>
+#include <utf8.h>
 
 using namespace testing;
 using std::string;
@@ -14,57 +15,64 @@ bool returnTrue(const string&) {
 }
 
 TEST(tokenizeText, simpleCases) {
-	EXPECT_THAT(tokenizeText(U"", returnTrue), IsEmpty());
-	EXPECT_THAT(tokenizeText(U"  \t\n\r\n ", returnTrue), IsEmpty());
+	EXPECT_THAT(tokenizeText("", returnTrue), IsEmpty());
+	EXPECT_THAT(tokenizeText("  \t\n\r\n ", returnTrue), IsEmpty());
 	EXPECT_THAT(
-		tokenizeText(U"Wit is educated insolence.", returnTrue),
+		tokenizeText("Wit is educated insolence.", returnTrue),
 		ElementsAre("wit", "is", "educated", "insolence")
 	);
 }
 
 TEST(tokenizeText, numbers) {
 	EXPECT_THAT(
-		tokenizeText(U"Henry V died at 36.", returnTrue),
+		tokenizeText("Henry V died at 36.", returnTrue),
 		ElementsAre("henry", "the", "fifth", "died", "at", "thirty", "six")
 	);
 	EXPECT_THAT(
-		tokenizeText(U"I spent $4.50 on gum.", returnTrue),
+		tokenizeText("I spent $4.50 on gum.", returnTrue),
 		ElementsAre("i", "spent", "four", "dollars", "fifty", "cents", "on", "gum")
 	);
 	EXPECT_THAT(
-		tokenizeText(U"I was born in 1982.", returnTrue),
+		tokenizeText("I was born in 1982.", returnTrue),
 		ElementsAre("i", "was", "born", "in", "nineteen", "eighty", "two")
 	);
 }
 
 TEST(tokenizeText, abbreviations) {
 	EXPECT_THAT(
-		tokenizeText(U"Prof. Foo lives on Dr. Dolittle Dr.", [](const string& word) { return word == "prof."; }),
+		tokenizeText("Prof. Foo lives on Dr. Dolittle Dr.", [](const string& word) { return word == "prof."; }),
 		ElementsAre("prof.", "foo", "lives", "on", "doctor", "dolittle", "drive")
 	);
 }
 
 TEST(tokenizeText, apostrophes) {
 	EXPECT_THAT(
-		tokenizeText(U"'Tis said he'd wish'd for a 'bus 'cause he wouldn't walk.", [](const string& word) { return word == "wouldn't"; }),
+		tokenizeText("'Tis said he'd wish'd for a 'bus 'cause he wouldn't walk.", [](const string& word) { return word == "wouldn't"; }),
 		ElementsAreArray(vector<string>{ "tis", "said", "he'd", "wish'd", "for", "a", "bus", "cause", "he", "wouldn't", "walk" })
 	);
 }
 
 TEST(tokenizeText, math) {
 	EXPECT_THAT(
-		tokenizeText(U"'1+2*3=7", returnTrue),
+		tokenizeText("'1+2*3=7", returnTrue),
 		ElementsAre("one", "plus", "two", "times", "three", "equals", "seven")
 	);
 }
 
+TEST(tokenizeText, unicodeCharacters) {
+	EXPECT_THAT(
+		tokenizeText("A naïve man called 晨 had piña colada and crème brûlée.", returnTrue),
+		ElementsAre("a", "naive", "man", "called", "had", "pina", "colada", "and", "creme", "brulee")
+	);
+}
+
 // Checks that each word contains only the characters a-z and the apostrophe
 TEST(tokenizeText, wordsUseLimitedCharacters) {
 	// Create string containing lots of undesirable characters
-	u32string input = U"A naïve man called 晨 was having piña colada and crème brûlée.";
+	string input = "A naïve man called 晨 was having piña colada and crème brûlée.";
 	for (char32_t c = 0; c <= 1000; ++c) {
-		input.append(U" ");
-		input.append(1, c);
+		input.append(" ");
+		utf8::append(c, back_inserter(input));
 	}
 
 	regex legal("^[a-z']+$");