diff --git a/src/buffer.cc b/src/buffer.cc
index c6ad506a..1fb9ab7e 100644
--- a/src/buffer.cc
+++ b/src/buffer.cc
@@ -59,10 +59,10 @@ BufferCoord Buffer::line_and_column_at(const BufferIterator& iterator) const
     return iterator.m_coord;
 }
 
-CharCount Buffer::line_length(LineCount line) const
+ByteCount Buffer::line_length(LineCount line) const
 {
     assert(line < line_count());
-    CharCount end = (line < line_count() - 1) ?
+    ByteCount end = (line < line_count() - 1) ?
                     m_lines[line + 1].start : character_count();
     return end - m_lines[line].start;
 }
@@ -75,8 +75,8 @@ BufferCoord Buffer::clamp(const BufferCoord& line_and_column,
 
     BufferCoord result(line_and_column.line, line_and_column.column);
     result.line = Kakoune::clamp(result.line, 0_line, line_count() - 1);
-    CharCount max_col = std::max(0_char, line_length(result.line) - (avoid_eol ? 2 : 1));
-    result.column = Kakoune::clamp(result.column, 0_char, max_col);
+    ByteCount max_col = std::max(0_byte, line_length(result.line) - (avoid_eol ? 2 : 1));
+    result.column = Kakoune::clamp(result.column, 0_byte, max_col);
     return result;
 }
 
@@ -116,7 +116,7 @@ BufferIterator Buffer::end() const
     return BufferIterator(*this, { line_count()-1, m_lines.back().length() });
 }
 
-CharCount Buffer::character_count() const
+ByteCount Buffer::character_count() const
 {
     if (m_lines.empty())
         return 0;
@@ -133,10 +133,10 @@ String Buffer::string(const BufferIterator& begin, const BufferIterator& end) co
     String res;
     for (LineCount line = begin.line(); line <= end.line(); ++line)
     {
-       CharCount start = 0;
+       ByteCount start = 0;
        if (line == begin.line())
            start = begin.column();
-       CharCount count = -1;
+       ByteCount count = -1;
        if (line == end.line())
            count = end.column() - start;
        res += m_lines[line].content.substr(start, count);
@@ -224,7 +224,7 @@ void Buffer::reset_undo_data()
 
 void Buffer::check_invariant() const
 {
-    CharCount start = 0;
+    ByteCount start = 0;
     assert(not m_lines.empty());
     for (auto& line : m_lines)
     {
@@ -239,7 +239,7 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
 {
     assert(pos.is_end() or utf8::is_character_start(pos));
     ++m_timestamp;
-    CharCount offset = pos.offset();
+    ByteCount offset = pos.offset();
 
     // all following lines advanced by length
     for (LineCount i = pos.line()+1; i < line_count(); ++i)
@@ -251,8 +251,8 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
     // line without inserting a '\n'
     if (pos == end() and (pos == begin() or *(pos-1) == '\n'))
     {
-        CharCount start = 0;
-        for (CharCount i = 0; i < content.length(); ++i)
+        ByteCount start = 0;
+        for (ByteCount i = 0; i < content.length(); ++i)
         {
             if (content[i] == '\n')
             {
@@ -274,8 +274,8 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
         auto line_it = m_lines.begin() + (int)pos.line();
         line_it = m_lines.erase(line_it);
 
-        CharCount start = 0;
-        for (CharCount i = 0; i < content.length(); ++i)
+        ByteCount start = 0;
+        for (ByteCount i = 0; i < content.length(); ++i)
         {
             if (content[i] == '\n')
             {
@@ -317,7 +317,7 @@ void Buffer::do_erase(const BufferIterator& begin, const BufferIterator& end)
     assert(utf8::is_character_start(begin) and
            (end.is_end() or utf8::is_character_start(end)));
     ++m_timestamp;
-    const CharCount length = end - begin;
+    const ByteCount length = end - begin;
     String prefix = m_lines[begin.line()].content.substr(0, begin.column());
     String suffix = m_lines[end.line()].content.substr(end.column());
     Line new_line = { m_lines[begin.line()].start, prefix + suffix };
@@ -351,7 +351,7 @@ void Buffer::apply_modification(const Modification& modification)
     }
     case Modification::Erase:
     {
-        CharCount count = modification.content.length();
+        ByteCount count = modification.content.length();
         BufferIterator end = modification.position + count;
         assert(string(modification.position, end) == modification.content);
         do_erase(modification.position, end);
diff --git a/src/buffer.hh b/src/buffer.hh
index 1a4e6694..d955bb14 100644
--- a/src/buffer.hh
+++ b/src/buffer.hh
@@ -17,14 +17,10 @@ namespace Kakoune
 class Buffer;
 class Window;
 
-struct BufferCoord : LineAndColumn<BufferCoord>
+struct BufferCoord : LineAndColumn<BufferCoord, LineCount, ByteCount>
 {
-    constexpr BufferCoord(LineCount line = 0, CharCount column = 0)
+    constexpr BufferCoord(LineCount line = 0, ByteCount column = 0)
         : LineAndColumn(line, column) {}
-
-    template<typename T>
-    explicit constexpr BufferCoord(const LineAndColumn<T>& other)
-        : LineAndColumn(other.line, other.column) {}
 };
 
 // A BufferIterator permits to iterate over the characters of a buffer
@@ -50,11 +46,11 @@ public:
     char   operator* () const;
     size_t operator- (const BufferIterator& iterator) const;
 
-    BufferIterator operator+ (CharCount size) const;
-    BufferIterator operator- (CharCount size) const;
+    BufferIterator operator+ (ByteCount size) const;
+    BufferIterator operator- (ByteCount size) const;
 
-    BufferIterator& operator+= (CharCount size);
-    BufferIterator& operator-= (CharCount size);
+    BufferIterator& operator+= (ByteCount size);
+    BufferIterator& operator-= (ByteCount size);
 
     BufferIterator& operator++ ();
     BufferIterator& operator-- ();
@@ -74,10 +70,10 @@ public:
     const Buffer& buffer() const;
     const BufferCoord& coord() const { return m_coord; }
     LineCount  line() const { return m_coord.line; }
-    CharCount column() const { return m_coord.column; }
+    ByteCount column() const { return m_coord.column; }
 
 private:
-    CharCount offset() const;
+    ByteCount offset() const;
 
     const Buffer* m_buffer;
     BufferCoord   m_coord;
@@ -130,9 +126,9 @@ public:
 
     BufferIterator begin() const;
     BufferIterator end() const;
-    CharCount      character_count() const;
+    ByteCount      character_count() const;
     LineCount      line_count() const;
-    CharCount      line_length(LineCount line) const;
+    ByteCount      line_length(LineCount line) const;
 
     // returns an iterator at given coordinates. line_and_column is
     // clamped according to avoid_eol.
@@ -188,10 +184,10 @@ private:
 
     struct Line
     {
-        CharCount start;
+        ByteCount start;
         String    content;
 
-        CharCount length() const { return content.length(); }
+        ByteCount length() const { return content.length(); }
     };
     struct LineList : std::vector<Line>
     {
diff --git a/src/buffer_iterator.inl.hh b/src/buffer_iterator.inl.hh
index 0738263a..950b7dfb 100644
--- a/src/buffer_iterator.inl.hh
+++ b/src/buffer_iterator.inl.hh
@@ -114,7 +114,7 @@ inline char BufferIterator::operator*() const
     return m_buffer->m_lines[line()].content[column()];
 }
 
-inline CharCount BufferIterator::offset() const
+inline ByteCount BufferIterator::offset() const
 {
     assert(m_buffer);
     return line() == 0 ? column()
@@ -127,12 +127,12 @@ inline size_t BufferIterator::operator-(const BufferIterator& iterator) const
     return (size_t)(int)(offset() - iterator.offset());
 }
 
-inline BufferIterator BufferIterator::operator+(CharCount size) const
+inline BufferIterator BufferIterator::operator+(ByteCount size) const
 {
     assert(m_buffer);
     if (size >= 0)
     {
-        CharCount o = std::min(m_buffer->character_count(), offset() + size);
+        ByteCount o = std::min(m_buffer->character_count(), offset() + size);
         for (LineCount i = line() + 1; i < m_buffer->line_count(); ++i)
         {
             if (m_buffer->m_lines[i].start > o)
@@ -144,12 +144,12 @@ inline BufferIterator BufferIterator::operator+(CharCount size) const
     return operator-(-size);
 }
 
-inline BufferIterator BufferIterator::operator-(CharCount size) const
+inline BufferIterator BufferIterator::operator-(ByteCount size) const
 {
     assert(m_buffer);
     if (size >= 0)
     {
-        CharCount o = std::max(0_char, offset() - size);
+        ByteCount o = std::max(0_byte, offset() - size);
         for (LineCount i = line(); i >= 0; --i)
         {
             if (m_buffer->m_lines[i].start <= o)
@@ -160,12 +160,12 @@ inline BufferIterator BufferIterator::operator-(CharCount size) const
     return operator+(-size);
 }
 
-inline BufferIterator& BufferIterator::operator+=(CharCount size)
+inline BufferIterator& BufferIterator::operator+=(ByteCount size)
 {
     return *this = (*this + size);
 }
 
-inline BufferIterator& BufferIterator::operator-=(CharCount size)
+inline BufferIterator& BufferIterator::operator-=(ByteCount size)
 {
     return *this = (*this - size);
 }
diff --git a/src/buffer_manager.cc b/src/buffer_manager.cc
index d2f7857f..764e1271 100644
--- a/src/buffer_manager.cc
+++ b/src/buffer_manager.cc
@@ -63,7 +63,7 @@ void BufferManager::set_last_used_buffer(Buffer& buffer)
 }
 
 CandidateList BufferManager::complete_buffername(const String& prefix,
-                                                 CharCount cursor_pos)
+                                                 ByteCount cursor_pos)
 {
     String real_prefix = prefix.substr(0, cursor_pos);
     CandidateList result;
diff --git a/src/buffer_manager.hh b/src/buffer_manager.hh
index ca84c9e8..d8065578 100644
--- a/src/buffer_manager.hh
+++ b/src/buffer_manager.hh
@@ -30,7 +30,7 @@ public:
     void    set_last_used_buffer(Buffer& buffer);
 
     CandidateList complete_buffername(const String& prefix,
-                                      CharCount cursor_pos = -1);
+                                      ByteCount cursor_pos = -1);
 
 private:
     BufferList m_buffers;
diff --git a/src/client.cc b/src/client.cc
index 11996f82..9802f623 100644
--- a/src/client.cc
+++ b/src/client.cc
@@ -134,7 +134,7 @@ public:
           m_completer(completer), m_callback(callback)
     {
         m_history_it = ms_history[m_prompt].end();
-        context.ui().print_status(m_prompt, m_prompt.length());
+        context.ui().print_status(m_prompt, m_prompt.char_length());
     }
 
     void on_key(const Key& key, Context& context) override
@@ -174,7 +174,7 @@ public:
                    m_saved_result = m_result;
                 auto it = m_history_it;
                 // search for the previous history entry matching typed prefix
-                CharCount prefix_length = m_saved_result.length();
+                ByteCount prefix_length = m_saved_result.length();
                 do
                 {
                     --it;
@@ -182,7 +182,7 @@ public:
                     {
                         m_history_it = it;
                         m_result     = *it;
-                        m_cursor_pos = m_result.length();
+                        m_cursor_pos = m_result.char_length();
                         break;
                     }
                 } while (it != history.begin());
@@ -193,7 +193,7 @@ public:
         {
             if (m_history_it != history.end())
             {
-                CharCount prefix_length = m_saved_result.length();
+                ByteCount prefix_length = m_saved_result.length();
                 // search for the next history entry matching typed prefix
                 ++m_history_it;
                 while (m_history_it != history.end() and
@@ -204,7 +204,7 @@ public:
                     m_result = *m_history_it;
                 else
                     m_result = m_saved_result;
-                m_cursor_pos = m_result.length();
+                m_cursor_pos = m_result.char_length();
             }
         }
         else if (key == Key::Left or
@@ -216,7 +216,7 @@ public:
         else if (key == Key::Right or
                  key == Key{Key::Modifiers::Control, 'f'})
         {
-            if (m_cursor_pos < m_result.length())
+            if (m_cursor_pos < m_result.char_length())
                 ++m_cursor_pos;
         }
         else if (key == Key::Backspace)
@@ -240,7 +240,7 @@ public:
             m_current_completion = -1;
             m_result = m_result.substr(0, m_cursor_pos) + reg
                      + m_result.substr(m_cursor_pos, String::npos);
-            m_cursor_pos += reg.length();
+            m_cursor_pos += reg.char_length();
         }
         else if (key == Key(Key::Modifiers::Control, 'i') or // tab completion
                  key == Key::BackTab)
@@ -250,7 +250,8 @@ public:
             // first try, we need to ask our completer for completions
             if (m_current_completion == -1)
             {
-                m_completions = m_completer(context, m_result, m_cursor_pos);
+                m_completions = m_completer(context, m_result,
+                                            m_result.byte_count_to(m_cursor_pos));
                 if (candidates.empty())
                     return;
 
@@ -272,16 +273,20 @@ public:
             context.ui().menu_select(m_current_completion);
             m_result = m_result.substr(0, m_completions.start) + completion
                      + m_result.substr(m_cursor_pos);
-            m_cursor_pos = m_completions.start + completion.length();
+            m_cursor_pos = m_result.char_count_to(m_completions.start)
+                         + completion.char_length();
         }
         else
         {
             context.ui().menu_hide();
             m_current_completion = -1;
-            m_result = m_result.substr(0, m_cursor_pos) + key.key + m_result.substr(m_cursor_pos, String::npos);
+            std::string keystr;
+            auto inserter = back_inserter(keystr);
+            utf8::dump(inserter, key.key);
+            m_result = m_result.substr(0, m_cursor_pos) + keystr + m_result.substr(m_cursor_pos, String::npos);
             ++m_cursor_pos;
         }
-        context.ui().print_status(m_prompt + m_result, m_prompt.length() + m_cursor_pos);
+        context.ui().print_status(m_prompt + m_result, m_prompt.char_length() + m_cursor_pos);
     }
 
 private:
diff --git a/src/command_manager.cc b/src/command_manager.cc
index b21921da..3998693d 100644
--- a/src/command_manager.cc
+++ b/src/command_manager.cc
@@ -61,7 +61,7 @@ private:
 
 
 using TokenList = std::vector<Token>;
-using TokenPosList = std::vector<std::pair<CharCount, CharCount>>;
+using TokenPosList = std::vector<std::pair<ByteCount, ByteCount>>;
 
 bool is_command_separator(char c)
 {
@@ -78,8 +78,8 @@ TokenList parse(const String& line,
 {
     TokenList result;
 
-    CharCount length = line.length();
-    CharCount pos = 0;
+    ByteCount length = line.length();
+    ByteCount pos = 0;
     while (pos < length)
     {
         while (pos != length)
@@ -97,7 +97,7 @@ TokenList parse(const String& line,
                 break;
         }
 
-        CharCount token_start = pos;
+        ByteCount token_start = pos;
 
         Token::Type type = Token::Type::Raw;
         if (line[pos] == '"' or line[pos] == '\'')
@@ -112,7 +112,7 @@ TokenList parse(const String& line,
         }
         else if (line[pos] == '%')
         {
-            CharCount type_start = ++pos;
+            ByteCount type_start = ++pos;
             while (isalpha(line[pos]))
                 ++pos;
             String type_name = line.substr(type_start, pos - type_start);
@@ -260,7 +260,7 @@ void CommandManager::execute(const String& command_line,
 }
 
 Completions CommandManager::complete(const Context& context,
-                                     const String& command_line, CharCount cursor_pos)
+                                     const String& command_line, ByteCount cursor_pos)
 {
     TokenPosList pos_info;
     TokenList tokens = parse(command_line, &pos_info);
@@ -277,7 +277,7 @@ Completions CommandManager::complete(const Context& context,
 
     if (token_to_complete == 0 or tokens.empty()) // command name completion
     {
-        CharCount cmd_start = tokens.empty() ? 0 : pos_info[0].first;
+        ByteCount cmd_start = tokens.empty() ? 0 : pos_info[0].first;
         Completions result(cmd_start, cursor_pos);
         String prefix = command_line.substr(cmd_start,
                                             cursor_pos - cmd_start);
@@ -302,10 +302,10 @@ Completions CommandManager::complete(const Context& context,
     if (command_it == m_commands.end() or not command_it->second.completer)
         return Completions();
 
-    CharCount start = token_to_complete < tokens.size() ?
+    ByteCount start = token_to_complete < tokens.size() ?
                    pos_info[token_to_complete].first : cursor_pos;
     Completions result(start , cursor_pos);
-    CharCount cursor_pos_in_token = cursor_pos - start;
+    ByteCount cursor_pos_in_token = cursor_pos - start;
 
     std::vector<String> params;
     for (auto token_it = tokens.begin()+1; token_it != tokens.end(); ++token_it)
@@ -319,7 +319,7 @@ Completions CommandManager::complete(const Context& context,
 CandidateList PerArgumentCommandCompleter::operator()(const Context& context,
                                                       const CommandParameters& params,
                                                       size_t token_to_complete,
-                                                      CharCount pos_in_token) const
+                                                      ByteCount pos_in_token) const
 {
     if (token_to_complete >= m_completers.size())
         return CandidateList();
diff --git a/src/command_manager.hh b/src/command_manager.hh
index 84f764ee..454ff95e 100644
--- a/src/command_manager.hh
+++ b/src/command_manager.hh
@@ -28,13 +28,13 @@ typedef std::function<void (const CommandParameters&,
 
 typedef std::function<CandidateList (const Context& context,
                                      const CommandParameters&,
-                                     size_t, CharCount)> CommandCompleter;
+                                     size_t, ByteCount)> CommandCompleter;
 
 class PerArgumentCommandCompleter
 {
 public:
     typedef std::function<CandidateList (const Context&,
-                                         const String&, CharCount)> ArgumentCompleter;
+                                         const String&, ByteCount)> ArgumentCompleter;
     typedef memoryview<ArgumentCompleter> ArgumentCompleterList;
 
     PerArgumentCommandCompleter(const ArgumentCompleterList& completers)
@@ -43,7 +43,7 @@ public:
     CandidateList operator()(const Context& context,
                              const CommandParameters& params,
                              size_t token_to_complete,
-                             CharCount pos_in_token) const;
+                             ByteCount pos_in_token) const;
 
 private:
     std::vector<ArgumentCompleter> m_completers;
@@ -57,7 +57,7 @@ public:
                  const EnvVarMap& env_vars = {});
 
     Completions complete(const Context& context,
-                         const String& command_line, CharCount cursor_pos);
+                         const String& command_line, ByteCount cursor_pos);
 
     bool command_defined(const String& command_name) const;
 
diff --git a/src/commands.cc b/src/commands.cc
index ddba6d61..97db7e5f 100644
--- a/src/commands.cc
+++ b/src/commands.cc
@@ -62,7 +62,7 @@ struct ParametersParser
         {
             if (params[i][0] == '-')
             {
-                auto it = options.find(params[i].substr(1));
+                auto it = options.find(params[i].substr(1_byte));
                 if (it == options.end())
                     throw unknown_option(params[i]);
 
@@ -88,7 +88,7 @@ struct ParametersParser
         assert(m_options.find(name) != m_options.end());
         for (auto& param : m_params)
         {
-            if (param[0] == '-' and param.substr(1) == name)
+            if (param[0] == '-' and param.substr(1_byte) == name)
                 return true;
 
             if (param == "--")
@@ -107,7 +107,7 @@ struct ParametersParser
 
         for (size_t i = 0; i < m_params.size(); ++i)
         {
-            if (m_params[i][0] == '-' and m_params[i].substr(1) == name)
+            if (m_params[i][0] == '-' and m_params[i].substr(1_byte) == name)
                 return m_params[i+1];
 
             if (m_params[i] == "--")
@@ -578,7 +578,7 @@ void define_command(const CommandParameters& params, Context& context)
     if (parser.has_option("file-completion"))
     {
         completer = [](const Context& context, const CommandParameters& params,
-                       size_t token_to_complete, CharCount pos_in_token)
+                       size_t token_to_complete, ByteCount pos_in_token)
         {
              const String& prefix = token_to_complete < params.size() ?
                                     params[token_to_complete] : String();
@@ -589,7 +589,7 @@ void define_command(const CommandParameters& params, Context& context)
     {
         String shell_cmd = parser.option_value("shell-completion");
         completer = [=](const Context& context, const CommandParameters& params,
-                        size_t token_to_complete, CharCount pos_in_token)
+                        size_t token_to_complete, ByteCount pos_in_token)
         {
            EnvVarMap vars = {
                {"token_to_complete", int_to_str(token_to_complete) },
@@ -778,7 +778,7 @@ void register_commands()
     cm.register_command("wq!", write_and_quit<true>);
 
     PerArgumentCommandCompleter buffer_completer({
-        [](const Context& context, const String& prefix, CharCount cursor_pos)
+        [](const Context& context, const String& prefix, ByteCount cursor_pos)
         { return BufferManager::instance().complete_buffername(prefix, cursor_pos); }
     });
     cm.register_commands({ "b", "buffer" }, show_buffer, buffer_completer);
@@ -786,7 +786,7 @@ void register_commands()
 
     cm.register_commands({ "ah", "addhl" }, add_highlighter,
                          [](const Context& context, const CommandParameters& params,
-                           size_t token_to_complete, CharCount pos_in_token)
+                           size_t token_to_complete, ByteCount pos_in_token)
                          {
                              Window& w = context.window();
                              const String& arg = token_to_complete < params.size() ?
@@ -800,7 +800,7 @@ void register_commands()
                          });
     cm.register_commands({ "rh", "rmhl" }, rm_highlighter,
                          [](const Context& context, const CommandParameters& params,
-                            size_t token_to_complete, CharCount pos_in_token)
+                            size_t token_to_complete, ByteCount pos_in_token)
                          {
                              Window& w = context.window();
                              const String& arg = token_to_complete < params.size() ?
@@ -814,7 +814,7 @@ void register_commands()
                          });
     cm.register_commands({ "af", "addfilter" }, add_filter,
                          [](const Context& context, const CommandParameters& params,
-                            size_t token_to_complete, CharCount pos_in_token)
+                            size_t token_to_complete, ByteCount pos_in_token)
                          {
                              Window& w = context.window();
                              const String& arg = token_to_complete < params.size() ?
@@ -828,7 +828,7 @@ void register_commands()
                          });
     cm.register_commands({ "rf", "rmfilter" }, rm_filter,
                          [](const Context& context, const CommandParameters& params,
-                            size_t token_to_complete, CharCount pos_in_token)
+                            size_t token_to_complete, ByteCount pos_in_token)
                          {
                              Window& w = context.window();
                              const String& arg = token_to_complete < params.size() ?
@@ -856,21 +856,21 @@ void register_commands()
                          [](const CommandParameters& params, Context& context)
                          { set_option(GlobalOptionManager::instance(), params, context); },
                          PerArgumentCommandCompleter({
-                             [](const Context& context, const String& prefix, CharCount cursor_pos)
+                             [](const Context& context, const String& prefix, ByteCount cursor_pos)
                              { return GlobalOptionManager::instance().complete_option_name(prefix, cursor_pos); }
                          }));
     cm.register_commands({ "setb", "setbuffer" },
                          [](const CommandParameters& params, Context& context)
                          { set_option(context.buffer().option_manager(), params, context); },
                          PerArgumentCommandCompleter({
-                             [](const Context& context, const String& prefix, CharCount cursor_pos)
+                             [](const Context& context, const String& prefix, ByteCount cursor_pos)
                              { return context.buffer().option_manager().complete_option_name(prefix, cursor_pos); }
                          }));
     cm.register_commands({ "setw", "setwindow" },
                          [](const CommandParameters& params, Context& context)
                          { set_option(context.window().option_manager(), params, context); },
                          PerArgumentCommandCompleter({
-                             [](const Context& context, const String& prefix, CharCount cursor_pos)
+                             [](const Context& context, const String& prefix, ByteCount cursor_pos)
                              { return context.window().option_manager().complete_option_name(prefix, cursor_pos); }
                          }));
 
diff --git a/src/completion.cc b/src/completion.cc
index 5db7ffb7..da5e1387 100644
--- a/src/completion.cc
+++ b/src/completion.cc
@@ -12,15 +12,15 @@ namespace Kakoune
 
 CandidateList complete_filename(const Context& context,
                                 const String& prefix,
-                                CharCount cursor_pos)
+                                ByteCount cursor_pos)
 {
     String real_prefix = parse_filename(prefix.substr(0, cursor_pos));
     String dirname = "./";
     String dirprefix;
     String fileprefix = real_prefix;
 
-    CharCount dir_end = -1;
-    for (CharCount i = 0; i < real_prefix.length(); ++i)
+    ByteCount dir_end = -1;
+    for (ByteCount i = 0; i < real_prefix.length(); ++i)
     {
         if (real_prefix[i] == '/')
             dir_end = i;
diff --git a/src/completion.hh b/src/completion.hh
index 60462975..cf626ec5 100644
--- a/src/completion.hh
+++ b/src/completion.hh
@@ -16,25 +16,25 @@ typedef std::vector<String> CandidateList;
 struct Completions
 {
     CandidateList candidates;
-    CharCount start;
-    CharCount end;
+    ByteCount start;
+    ByteCount end;
 
     Completions()
         : start(0), end(0) {}
 
-    Completions(CharCount start, CharCount end)
+    Completions(ByteCount start, ByteCount end)
         : start(start), end(end) {}
 };
 
 CandidateList complete_filename(const Context& context,
                                 const String& prefix,
-                                CharCount cursor_pos = -1);
+                                ByteCount cursor_pos = -1);
 
 typedef std::function<Completions (const Context&,
-                                   const String&, CharCount)> Completer;
+                                   const String&, ByteCount)> Completer;
 
 inline Completions complete_nothing(const Context& context,
-                                    const String&, CharCount cursor_pos)
+                                    const String&, ByteCount cursor_pos)
 {
     return Completions(cursor_pos, cursor_pos);
 }
diff --git a/src/display_buffer.hh b/src/display_buffer.hh
index e1f1442f..aa54f1f6 100644
--- a/src/display_buffer.hh
+++ b/src/display_buffer.hh
@@ -7,18 +7,15 @@
 #include "color.hh"
 #include "line_and_column.hh"
 #include "buffer.hh"
+#include "utf8.hh"
 
 namespace Kakoune
 {
 
-struct DisplayCoord : LineAndColumn<DisplayCoord>
+struct DisplayCoord : LineAndColumn<DisplayCoord, LineCount, CharCount>
 {
     constexpr DisplayCoord(LineCount line = 0, CharCount column = 0)
         : LineAndColumn(line, column) {}
-
-    template<typename T>
-    explicit constexpr DisplayCoord(const LineAndColumn<T>& other)
-        : LineAndColumn(other.line, other.column) {}
 };
 
 typedef int Attribute;
@@ -64,10 +61,10 @@ public:
         switch (m_type)
         {
             case BufferRange:
-               return m_end - m_begin;
+               return utf8::distance(m_begin, m_end);
             case Text:
             case ReplacedBufferRange:
-               return m_text.length();
+               return m_text.char_length();
         }
     }
 
diff --git a/src/editor.cc b/src/editor.cc
index ff77e357..1a4cfdb7 100644
--- a/src/editor.cc
+++ b/src/editor.cc
@@ -129,9 +129,9 @@ void Editor::move_selections(CharCount offset, SelectMode mode)
     for (auto& sel : m_selections)
     {
         auto last = sel.last();
-        last = clamp(utf8::advance(last, offset),
-                     buffer().iterator_at_line_begin(last),
-                     utf8::previous(buffer().iterator_at_line_end(last)));
+        auto limit = offset < 0 ? buffer().iterator_at_line_begin(last)
+                                : utf8::previous(buffer().iterator_at_line_end(last));
+        last = utf8::advance(last, limit, offset);
         sel.selection = Selection(mode == SelectMode::Extend ? sel.first() : last, last);
     }
     merge_overlapping(m_selections);
diff --git a/src/file.cc b/src/file.cc
index 2723893e..b05b5782 100644
--- a/src/file.cc
+++ b/src/file.cc
@@ -4,6 +4,8 @@
 #include "buffer_manager.hh"
 #include "assert.hh"
 
+#include "unicode.hh"
+
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -14,25 +16,20 @@
 namespace Kakoune
 {
 
-bool isidentifier(char c)
-{
-    return std::isalnum(c) or c == '_';
-}
-
 String parse_filename(const String& filename)
 {
     if (filename.length() >= 2 and filename[0] == '~' and filename[1] == '/')
-        return parse_filename("$HOME/" + filename.substr(2));
+        return parse_filename("$HOME/" + filename.substr(2_byte));
 
-    CharCount pos = 0;
+    ByteCount pos = 0;
     String result;
-    for (CharCount i = 0; i < filename.length(); ++i)
+    for (ByteCount i = 0; i < filename.length(); ++i)
     {
         if (filename[i] == '$' and (i == 0 or filename[i-1] != '\\'))
         {
             result += filename.substr(pos, i - pos);
-            CharCount end = i+1;
-            while (end != filename.length() and isidentifier(filename[end]))
+            ByteCount end = i+1;
+            while (end != filename.length() and is_word(filename[end]))
                 ++end;
             String var_name = filename.substr(i+1, end - i - 1);
             const char* var_value = getenv(var_name.c_str());
diff --git a/src/filter_group.cc b/src/filter_group.cc
index ea44bffa..ac10faee 100644
--- a/src/filter_group.cc
+++ b/src/filter_group.cc
@@ -40,13 +40,13 @@ FilterGroup& FilterGroup::get_group(const String& id)
 
 
 CandidateList FilterGroup::complete_id(const String& prefix,
-                                       CharCount cursor_pos)
+                                       ByteCount cursor_pos)
 {
     return m_filters.complete_id(prefix, cursor_pos);
 }
 
 CandidateList FilterGroup::complete_group_id(const String& prefix,
-                                             CharCount cursor_pos)
+                                             ByteCount cursor_pos)
 {
     return m_filters.complete_id_if(
         prefix, cursor_pos,
diff --git a/src/filter_group.hh b/src/filter_group.hh
index 8c93936b..df3cbb9f 100644
--- a/src/filter_group.hh
+++ b/src/filter_group.hh
@@ -19,8 +19,8 @@ public:
 
     FilterGroup& get_group(const String& id);
 
-    CandidateList complete_id(const String& prefix, CharCount cursor_pos);
-    CandidateList complete_group_id(const String& prefix, CharCount cursor_pos);
+    CandidateList complete_id(const String& prefix, ByteCount cursor_pos);
+    CandidateList complete_group_id(const String& prefix, ByteCount cursor_pos);
 
 private:
     idvaluemap<String, FilterFunc> m_filters;
diff --git a/src/filter_registry.cc b/src/filter_registry.cc
index 65070bdf..1a2a1754 100644
--- a/src/filter_registry.cc
+++ b/src/filter_registry.cc
@@ -31,7 +31,7 @@ void FilterRegistry::add_filter_to_group(FilterGroup& group,
 }
 
 CandidateList FilterRegistry::complete_filter(const String& prefix,
-                                              CharCount cursor_pos)
+                                              ByteCount cursor_pos)
 {
     return m_factories.complete_id(prefix, cursor_pos);
 }
diff --git a/src/filter_registry.hh b/src/filter_registry.hh
index 77763782..0756091c 100644
--- a/src/filter_registry.hh
+++ b/src/filter_registry.hh
@@ -30,7 +30,7 @@ public:
                              const FilterParameters& parameters);
 
     CandidateList complete_filter(const String& prefix,
-                                  CharCount cursor_pos);
+                                  ByteCount cursor_pos);
 
 private:
     idvaluemap<String, FilterFactory> m_factories;
diff --git a/src/highlighter_group.cc b/src/highlighter_group.cc
index 57b21a5c..1dac5fe9 100644
--- a/src/highlighter_group.cc
+++ b/src/highlighter_group.cc
@@ -39,13 +39,13 @@ HighlighterGroup& HighlighterGroup::get_group(const String& id)
 
 
 CandidateList HighlighterGroup::complete_id(const String& prefix,
-                                            CharCount cursor_pos)
+                                            ByteCount cursor_pos)
 {
     return m_highlighters.complete_id(prefix, cursor_pos);
 }
 
 CandidateList HighlighterGroup::complete_group_id(const String& prefix,
-                                                  CharCount cursor_pos)
+                                                  ByteCount cursor_pos)
 {
     return m_highlighters.complete_id_if(
         prefix, cursor_pos,
diff --git a/src/highlighter_group.hh b/src/highlighter_group.hh
index 9b4f1bf0..50c883e7 100644
--- a/src/highlighter_group.hh
+++ b/src/highlighter_group.hh
@@ -22,8 +22,8 @@ public:
 
     HighlighterGroup& get_group(const String& id);
 
-    CandidateList complete_id(const String& prefix, CharCount cursor_pos);
-    CandidateList complete_group_id(const String& prefix, CharCount cursor_pos);
+    CandidateList complete_id(const String& prefix, ByteCount cursor_pos);
+    CandidateList complete_group_id(const String& prefix, ByteCount cursor_pos);
 
 private:
     idvaluemap<String, HighlighterFunc> m_highlighters;
diff --git a/src/highlighter_registry.cc b/src/highlighter_registry.cc
index 46038aa3..90cbe36f 100644
--- a/src/highlighter_registry.cc
+++ b/src/highlighter_registry.cc
@@ -33,7 +33,7 @@ void HighlighterRegistry::add_highlighter_to_group(Window& window,
 }
 
 CandidateList HighlighterRegistry::complete_highlighter(const String& prefix,
-                                                        CharCount cursor_pos)
+                                                        ByteCount cursor_pos)
 {
     return m_factories.complete_id(prefix, cursor_pos);
 }
diff --git a/src/highlighter_registry.hh b/src/highlighter_registry.hh
index 2a3f740d..9690318d 100644
--- a/src/highlighter_registry.hh
+++ b/src/highlighter_registry.hh
@@ -30,7 +30,7 @@ public:
                                   const HighlighterParameters& parameters);
 
     CandidateList complete_highlighter(const String& prefix,
-                                      CharCount cursor_pos);
+                                      ByteCount cursor_pos);
 
 private:
     idvaluemap<String, HighlighterFactory> m_factories;
diff --git a/src/idvaluemap.hh b/src/idvaluemap.hh
index c65f35fc..e11c327a 100644
--- a/src/idvaluemap.hh
+++ b/src/idvaluemap.hh
@@ -65,7 +65,7 @@ public:
 
     template<typename _Condition>
     CandidateList complete_id_if(const String& prefix,
-                                 CharCount cursor_pos,
+                                 ByteCount cursor_pos,
                                  _Condition condition)
     {
         String real_prefix = prefix.substr(0, cursor_pos);
@@ -83,7 +83,7 @@ public:
     }
 
     CandidateList complete_id(const String& prefix,
-                              CharCount cursor_pos)
+                              ByteCount cursor_pos)
     {
         return complete_id_if(
             prefix, cursor_pos, [](const value_type&) { return true; });
diff --git a/src/keys.cc b/src/keys.cc
index 18b31d77..6b2479ff 100644
--- a/src/keys.cc
+++ b/src/keys.cc
@@ -25,11 +25,11 @@ static std::unordered_map<String, Codepoint> keynamemap = {
 KeyList parse_keys(const String& str)
 {
     KeyList result;
-    for (CharCount pos = 0; pos < str.length(); ++pos)
+    for (ByteCount pos = 0; pos < str.length(); ++pos)
     {
         if (str[pos] == '<')
         {
-            CharCount end_pos = pos;
+            ByteCount end_pos = pos;
             while (end_pos < str.length() and str[end_pos] != '>')
                 ++end_pos;
 
@@ -43,12 +43,12 @@ KeyList parse_keys(const String& str)
                     if (tolower(keyname[0]) == 'c' and keyname[1] == '-')
                     {
                         modifier = Key::Modifiers::Control;
-                        keyname = keyname.substr(2);
+                        keyname = keyname.substr(2_byte);
                     }
                     if (tolower(keyname[0]) == 'a' and keyname[1] == '-')
                     {
                         modifier = Key::Modifiers::Alt;
-                        keyname = keyname.substr(2);
+                        keyname = keyname.substr(2_byte);
                     }
                 }
                 if (keyname.length() == 1)
diff --git a/src/line_and_column.hh b/src/line_and_column.hh
index 5a278a4f..aaffb222 100644
--- a/src/line_and_column.hh
+++ b/src/line_and_column.hh
@@ -6,13 +6,13 @@
 namespace Kakoune
 {
 
-template<typename EffectiveType>
+template<typename EffectiveType, typename LineType, typename ColumnType>
 struct LineAndColumn
 {
-    LineCount line;
-    CharCount column;
+    LineType   line;
+    ColumnType column;
 
-    constexpr LineAndColumn(LineCount line = 0, CharCount column = 0)
+    constexpr LineAndColumn(LineType line = 0, ColumnType column = 0)
         : line(line), column(column) {}
 
     constexpr EffectiveType operator+(const EffectiveType& other) const
diff --git a/src/main.cc b/src/main.cc
index acd32819..4761d6ff 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -263,20 +263,22 @@ void do_scroll(Context& context)
                   "do_scrool only implements PageUp and PageDown");
     Window& window = context.window();
     Buffer& buffer = context.buffer();
-    BufferCoord position = window.position();
-    BufferIterator cursor_pos;
+    DisplayCoord position = window.position();
+    LineCount cursor_line = 0;
 
     if (key == Key::PageUp)
     {
         position.line -= (window.dimensions().line - 2);
-        cursor_pos = buffer.iterator_at(position);
+        cursor_line = position.line;
     }
     else if (key == Key::PageDown)
     {
         position.line += (window.dimensions().line - 2);
-        cursor_pos = buffer.iterator_at(position + BufferCoord{window.dimensions().line - 1, 0});
+        cursor_line = position.line + window.dimensions().line - 1;
     }
-
+    auto cursor_pos = utf8::advance(buffer.iterator_at_line_begin(position.line),
+                                    buffer.iterator_at_line_end(position.line),
+                                    position.column);
     window.select(cursor_pos);
     window.set_position(position);
 }
@@ -473,7 +475,7 @@ int main(int argc, char* argv[])
                                    { return runtime_directory(); });
     shell_manager.register_env_var("opt_.+",
                                    [](const String& name, const Context& context)
-                                   { return context.option_manager()[name.substr(4)].as_string(); });
+                                   { return context.option_manager()[name.substr(4_byte)].as_string(); });
     shell_manager.register_env_var("reg_.+",
                                    [](const String& name, const Context& context)
                                    { return RegisterManager::instance()[name[4]].values(context)[0]; });
diff --git a/src/ncurses.cc b/src/ncurses.cc
index 68001876..2f9ab649 100644
--- a/src/ncurses.cc
+++ b/src/ncurses.cc
@@ -227,21 +227,17 @@ void NCursesUI::print_status(const String& status, CharCount cursor_pos)
     move(y-1, 0);
     clrtoeol();
     if (cursor_pos == -1)
-       addstr(status.c_str());
-    else if (cursor_pos < status.length())
-    {
-       addstr(status.substr(0, cursor_pos).c_str());
-       set_attribute(A_REVERSE, 1);
-       addch(status[cursor_pos]);
-       set_attribute(A_REVERSE, 0);
-       addstr(status.substr(cursor_pos+1, -1).c_str());
-    }
+       addutf8str(status.begin(), status.end());
     else
     {
-       addstr(status.c_str());
-       set_attribute(A_REVERSE, 1);
-       addch(' ');
-       set_attribute(A_REVERSE, 0);
+        auto cursor_it = utf8::advance(status.begin(), status.end(), (int)cursor_pos);
+        auto end = status.end();
+        addutf8str(status.begin(), cursor_it);
+        set_attribute(A_REVERSE, 1);
+        addch((cursor_it == end) ? ' ' : utf8::codepoint(cursor_it));
+        set_attribute(A_REVERSE, 0);
+        if (cursor_it != end)
+            addutf8str(utf8::next(cursor_it), end);
     }
     redraw(m_menu_win);
 }
@@ -256,7 +252,7 @@ void NCursesUI::menu_show(const memoryview<String>& choices,
     for (int i = 0; i < m_choices.size(); ++i)
     {
         m_items.push_back(new_item(m_choices[i].c_str(), ""));
-        longest = std::max(longest, m_choices[i].length());
+        longest = std::max(longest, m_choices[i].char_length());
     }
     m_items.push_back(nullptr);
     longest += 1;
diff --git a/src/option_manager.cc b/src/option_manager.cc
index 1a09361d..b2123cfe 100644
--- a/src/option_manager.cc
+++ b/src/option_manager.cc
@@ -57,7 +57,7 @@ const Option& OptionManager::operator[](const String& name) const
 }
 
 CandidateList OptionManager::complete_option_name(const String& prefix,
-                                                  CharCount cursor_pos)
+                                                  ByteCount cursor_pos)
 {
     String real_prefix = prefix.substr(0, cursor_pos);
     CandidateList result;
diff --git a/src/option_manager.hh b/src/option_manager.hh
index 221239fd..2fa2f296 100644
--- a/src/option_manager.hh
+++ b/src/option_manager.hh
@@ -57,7 +57,7 @@ public:
     void set_option(const String& name, const Option& value);
 
     CandidateList complete_option_name(const String& prefix,
-                                       CharCount cursor_pos);
+                                       ByteCount cursor_pos);
 
     typedef std::unordered_map<String, Option> OptionMap;
     OptionMap flatten_options() const;
diff --git a/src/string.hh b/src/string.hh
index dfcd9cbb..0b24a15f 100644
--- a/src/string.hh
+++ b/src/string.hh
@@ -3,10 +3,12 @@
 
 #include <string>
 #include <iosfwd>
+#include <climits>
 #include <boost/regex.hpp>
 
 #include "memoryview.hh"
 #include "units.hh"
+#include "utf8.hh"
 
 namespace Kakoune
 {
@@ -25,8 +27,11 @@ public:
    template<typename Iterator>
    String(Iterator begin, Iterator end) : m_content(begin, end) {}
 
-   char      operator[](CharCount pos) const { return m_content[(int)pos]; }
-   CharCount length() const { return m_content.length(); }
+   char      operator[](ByteCount pos) const { return m_content[(int)pos]; }
+   ByteCount length() const { return m_content.length(); }
+   CharCount char_length() const { return utf8::distance(begin(), end()); }
+   ByteCount byte_count_to(CharCount count) const { return utf8::advance(begin(), end(), (int)count) - begin(); }
+   CharCount char_count_to(ByteCount count) const { return utf8::distance(begin(), begin() + (int)count); }
    bool      empty()  const { return m_content.empty(); }
 
    bool      operator== (const String& other) const { return m_content == other.m_content; }
@@ -45,7 +50,13 @@ public:
    memoryview<char> data()  const { return memoryview<char>(m_content.data(), m_content.size()); }
    const char*      c_str() const { return m_content.c_str(); }
 
-   String substr(CharCount pos, CharCount length = -1) const { return String(m_content.substr((int)pos, (int)length)); }
+   String substr(ByteCount pos, ByteCount length = -1) const { return String(m_content.substr((int)pos, (int)length)); }
+   String substr(CharCount pos, CharCount length = INT_MAX) const
+   {
+       auto b = utf8::advance(begin(), end(), (int)pos);
+       auto e = utf8::advance(b, end(), (int)length);
+       return String(b,e);
+   }
    String replace(const String& expression, const String& replacement) const;
 
    using iterator = std::string::const_iterator;
diff --git a/src/utf8.hh b/src/utf8.hh
index 057f1d59..0f136c68 100644
--- a/src/utf8.hh
+++ b/src/utf8.hh
@@ -43,17 +43,17 @@ Iterator previous(Iterator it)
 // dth character after (or before if d < 0) the character
 // pointed by it
 template<typename Iterator, typename Distance>
-Iterator advance(Iterator it, Distance d)
+Iterator advance(Iterator it, Iterator end, Distance d)
 {
     if (d < 0)
     {
-       while (d++)
-           it = previous(it);
+       while (it != end and d++)
+           it = utf8::previous(it);
     }
     else
     {
-        while (d--)
-           it = next(it);
+        while (it != end and d--)
+           it = utf8::next(it);
     }
     return it;
 }
diff --git a/src/window.cc b/src/window.cc
index 7e62264a..e74098c0 100644
--- a/src/window.cc
+++ b/src/window.cc
@@ -51,18 +51,14 @@ void Window::update_display_buffer()
         LineCount buffer_line = m_position.line + line;
         if (buffer_line >= buffer().line_count())
             break;
-        BufferIterator pos        = buffer().iterator_at({ buffer_line, m_position.column });
-        BufferIterator line_begin = buffer().iterator_at_line_begin(pos);
-        BufferIterator line_end   = buffer().iterator_at_line_end(pos);
+        BufferIterator line_begin = buffer().iterator_at_line_begin(buffer_line);
+        BufferIterator line_end   = buffer().iterator_at_line_end(buffer_line);
 
-        BufferIterator end;
-        if (CharCount(line_end - pos) > m_dimensions.column)
-            end = pos + m_dimensions.column;
-        else
-            end = line_end;
+        BufferIterator begin = utf8::advance(line_begin, line_end, (int)m_position.column);
+        BufferIterator end   = utf8::advance(begin,      line_end, (int)m_dimensions.column);
 
         lines.push_back(DisplayLine(buffer_line));
-        lines.back().push_back(DisplayAtom(AtomContent(pos,end)));
+        lines.back().push_back(DisplayAtom(AtomContent(begin, end)));
     }
 
     m_display_buffer.compute_range();
@@ -107,20 +103,20 @@ void Window::scroll_to_keep_cursor_visible_ifn()
             atom.content.begin() <= cursor and atom.content.end() > cursor)
         {
             if (atom.content.type() == AtomContent::BufferRange)
-                column += cursor - atom.content.begin();
+                column += utf8::distance(atom.content.begin(), cursor);
             else
-                column += atom.content.content().length();
+                column += atom.content.content().char_length();
 
             // we could early out on this, but having scrolling left
             // faster than not scrolling at all is not really useful.
-            if (cursor.column() < m_position.column)
-                m_position.column = cursor.column();
+            if (column < m_position.column)
+                m_position.column = column;
             else if (column >= m_position.column + m_dimensions.column)
                 m_position.column = column - (m_dimensions.column - 1);
 
             return;
         }
-        column += atom.content.content().length();
+        column += atom.content.content().char_length();
     }
     if (cursor != buffer().end())
     {
diff --git a/src/window.hh b/src/window.hh
index 6e2d59d6..79310ddb 100644
--- a/src/window.hh
+++ b/src/window.hh
@@ -24,8 +24,8 @@ class Window : public Editor, public OptionManagerWatcher
 public:
     ~Window();
 
-    const BufferCoord& position() const { return m_position; }
-    void set_position(const BufferCoord& position) { m_position = buffer().clamp(position); }
+    const DisplayCoord& position() const { return m_position; }
+    void set_position(const DisplayCoord& position) { m_position = position; }
 
     const DisplayCoord& dimensions() const { return m_dimensions; }
     void set_dimensions(const DisplayCoord& dimensions);
@@ -58,7 +58,7 @@ private:
 
     void scroll_to_keep_cursor_visible_ifn();
 
-    BufferCoord   m_position;
+    DisplayCoord  m_position;
     DisplayCoord  m_dimensions;
     DisplayBuffer m_display_buffer;