diff --git a/include/rfl/avro/Writer.hpp b/include/rfl/avro/Writer.hpp
index 4cdf2832..6a6f1528 100644
--- a/include/rfl/avro/Writer.hpp
+++ b/include/rfl/avro/Writer.hpp
@@ -147,7 +147,8 @@ class RFL_API Writer {
   OutputVarType add_value_to_map(const std::string_view& _name, const T& _var,
                                  OutputMapType* _parent) const {
     avro_value_t new_value;
-    int result = avro_value_add(&_parent->val_, _name.data(), &new_value,
+    // Copy name to nullterminate.
+    int result = avro_value_add(&_parent->val_, std::string(_name).c_str(), &new_value,
                                 nullptr, nullptr);
     if (result != 0) {
       throw std::runtime_error("Error adding value to map: error(" +
@@ -163,7 +164,8 @@ class RFL_API Writer {
                                     const T& _var,
                                     OutputObjectType* _parent) const {
     avro_value_t new_value;
-    int result = avro_value_get_by_name(&_parent->val_, _name.data(),
+    // Copy name to nullterminate.
+    int result = avro_value_get_by_name(&_parent->val_, std::string(_name).c_str(),
                                         &new_value, nullptr);
     if (result != 0) {
       throw std::runtime_error("Error adding value to object: error(" +
diff --git a/include/rfl/capnproto/Reader.hpp b/include/rfl/capnproto/Reader.hpp
index 819a5f3e..684b2c55 100644
--- a/include/rfl/capnproto/Reader.hpp
+++ b/include/rfl/capnproto/Reader.hpp
@@ -165,8 +165,8 @@ class RFL_API Reader {
       const auto entries = _map.val_.get("entries").as<capnp::DynamicList>();
       for (auto entry : entries) {
         auto s = entry.template as<capnp::DynamicStruct>();
-        const char* key = s.get("key").as<capnp::Text>().cStr();
-        _map_reader.read(std::string_view(key), InputVarType{s.get("value")});
+        const auto key = s.get("key").as<capnp::Text>();
+        _map_reader.read(std::string_view(key.cStr(), key.size()), InputVarType{s.get("value")});
       }
       return std::nullopt;
     } catch (std::exception& e) {
diff --git a/include/rfl/capnproto/Writer.hpp b/include/rfl/capnproto/Writer.hpp
index 0eaf4f84..cd9bf9bd 100644
--- a/include/rfl/capnproto/Writer.hpp
+++ b/include/rfl/capnproto/Writer.hpp
@@ -193,7 +193,7 @@ class RFL_API Writer {
     auto entries =
         OutputArrayType{_parent->val_.get("entries").as<capnp::DynamicList>()};
     auto new_entry = add_object_to_array(2, &entries);
-    add_value_to_object("key", std::string(_name), &new_entry);
+    new_entry.val_.set("key", { _name.data(), _name.size() });
     return add_value_to_object("value", _var, &new_entry);
   }
 
@@ -202,20 +202,20 @@ class RFL_API Writer {
                                     const T& _var,
                                     OutputObjectType* _parent) const {
     if constexpr (std::is_same<std::remove_cvref_t<T>, std::string>()) {
-      _parent->val_.set(_name.data(), _var.c_str());
+      _parent->val_.set({ _name.data(), _name.size() }, { _var.c_str(), _var.size() });
 
     } else if constexpr (std::is_same<std::remove_cvref_t<T>,
                                       rfl::Bytestring>()) {
       const auto array_ptr = kj::ArrayPtr<const kj::byte>(
           internal::ptr_cast<const unsigned char*>(_var.data()), _var.size());
-      _parent->val_.set(_name.data(), capnp::Data::Reader(array_ptr));
+      _parent->val_.set({ _name.data(), _name.size() }, capnp::Data::Reader(array_ptr));
 
     } else if constexpr (std::is_floating_point<std::remove_cvref_t<T>>() ||
                          std::is_same<std::remove_cvref_t<T>, bool>()) {
-      _parent->val_.set(_name.data(), _var);
+      _parent->val_.set({ _name.data(), _name.size() }, _var);
 
     } else if constexpr (std::is_integral<std::remove_cvref_t<T>>()) {
-      _parent->val_.set(_name.data(), static_cast<std::int64_t>(_var));
+      _parent->val_.set({ _name.data(), _name.size() }, static_cast<std::int64_t>(_var));
 
     } else if constexpr (internal::is_literal_v<T>) {
       return add_value_to_object(_name, _var.value(), _parent);
diff --git a/include/rfl/json/Reader.hpp b/include/rfl/json/Reader.hpp
index b358e71f..ac86ad84 100644
--- a/include/rfl/json/Reader.hpp
+++ b/include/rfl/json/Reader.hpp
@@ -88,7 +88,7 @@ struct Reader {
     yyjson_obj_iter_init(_obj.val_, &iter);
     yyjson_val* key;
     while ((key = yyjson_obj_iter_next(&iter))) {
-      const auto name = std::string_view(yyjson_get_str(key));
+      const auto name = std::string_view(yyjson_get_str(key), yyjson_get_len(key));
       _object_reader.read(name, InputVarType(yyjson_obj_iter_get_val(key)));
     }
     return std::nullopt;
@@ -101,7 +101,7 @@ struct Reader {
       if (r == NULL) {
         return error("Could not cast to string.");
       }
-      return std::string(r);
+      return std::string(r, yyjson_get_len(_var.val_));
 
     } else if constexpr (std::is_same<std::remove_cvref_t<T>, bool>()) {
       if (!yyjson_is_bool(_var.val_)) {
diff --git a/include/rfl/json/Writer.hpp b/include/rfl/json/Writer.hpp
index 159c0e0e..951752db 100644
--- a/include/rfl/json/Writer.hpp
+++ b/include/rfl/json/Writer.hpp
@@ -96,7 +96,7 @@ class RFL_API Writer {
                                     OutputObjectType* _parent) const {
     const auto val = from_basic_type(_var);
     const bool ok = yyjson_mut_obj_add(
-        _parent->val_, yyjson_mut_strcpy(doc(), _name.data()), val.val_);
+        _parent->val_, yyjson_mut_strncpy(doc(), _name.data(), _name.size()), val.val_);
     if (!ok) {
       throw std::runtime_error("Could not add field '" + std::string(_name) +
                                "' to object.");
@@ -117,7 +117,7 @@ class RFL_API Writer {
   template <class T>
   OutputVarType from_basic_type(const T& _var) const noexcept {
     if constexpr (std::is_same<std::remove_cvref_t<T>, std::string>()) {
-      return OutputVarType(yyjson_mut_strcpy(doc(), _var.c_str()));
+      return OutputVarType(yyjson_mut_strncpy(doc(), _var.c_str(), _var.size()));
 
     } else if constexpr (std::is_same<std::remove_cvref_t<T>, bool>()) {
       return OutputVarType(yyjson_mut_bool(doc(), _var));
diff --git a/include/rfl/xml/Writer.hpp b/include/rfl/xml/Writer.hpp
index bd20febe..e68582ce 100644
--- a/include/rfl/xml/Writer.hpp
+++ b/include/rfl/xml/Writer.hpp
@@ -93,9 +93,9 @@ struct RFL_API Writer {
 
  private:
   template <class T>
-  std::string to_string(const T& _val) const {
+  decltype(auto) to_string(const T& _val) const {
     if constexpr (std::is_same<std::remove_cvref_t<T>, std::string>()) {
-      return _val;
+      return _val; // Return reference to avoid expensive string copy.
     } else if constexpr (std::is_same<std::remove_cvref_t<T>, bool>()) {
       return _val ? "true" : "false";
     } else if constexpr (std::is_floating_point<std::remove_cvref_t<T>>() ||
diff --git a/include/rfl/yaml/Writer.hpp b/include/rfl/yaml/Writer.hpp
index 549e6d42..b5bf0616 100644
--- a/include/rfl/yaml/Writer.hpp
+++ b/include/rfl/yaml/Writer.hpp
@@ -77,7 +77,6 @@ class RFL_API Writer {
 
   void end_object(OutputObjectType* _obj) const;
 
- private:
   template <class T>
   OutputVarType insert_value(const std::string_view& _name,
                              const T& _var) const {
@@ -85,14 +84,14 @@ class RFL_API Writer {
                   std::is_same<std::remove_cvref_t<T>, bool>() ||
                   std::is_same<std::remove_cvref_t<T>,
                                std::remove_cvref_t<decltype(YAML::Null)>>()) {
-      (*out_) << YAML::Key << _name.data() << YAML::Value << _var;
+      (*out_) << YAML::Key << std::string(_name) << YAML::Value << _var;
     } else if constexpr (std::is_floating_point<std::remove_cvref_t<T>>()) {
       // std::to_string is necessary to ensure that floating point values are
       // always written as floats.
-      (*out_) << YAML::Key << _name.data() << YAML::Value
+      (*out_) << YAML::Key << std::string(_name) << YAML::Value
               << std::to_string(_var);
     } else if constexpr (std::is_integral<std::remove_cvref_t<T>>()) {
-      (*out_) << YAML::Key << _name.data() << YAML::Value
+      (*out_) << YAML::Key << std::string(_name) << YAML::Value
               << static_cast<int64_t>(_var);
     } else {
       static_assert(rfl::always_false_v<T>, "Unsupported type.");
diff --git a/src/rfl/capnproto/Writer.cpp b/src/rfl/capnproto/Writer.cpp
index 9220142e..18e17a0a 100644
--- a/src/rfl/capnproto/Writer.cpp
+++ b/src/rfl/capnproto/Writer.cpp
@@ -47,7 +47,7 @@ Writer::OutputArrayType Writer::add_array_to_map(const std::string_view& _name,
 Writer::OutputArrayType Writer::add_array_to_object(
     const std::string_view& _name, const size_t _size,
     OutputObjectType* _parent) const {
-  return OutputArrayType{_parent->val_.init(_name.data(), SafeSizeToUInt(_size))
+  return OutputArrayType{_parent->val_.init({ _name.data(), _name.size() }, SafeSizeToUInt(_size))
                              .as<capnp::DynamicList>()};
 }
 
@@ -111,7 +111,7 @@ Writer::OutputObjectType Writer::add_object_to_object(
     const std::string_view& _name, const size_t /*_size*/,
     OutputObjectType* _parent) const {
   return OutputObjectType{
-      _parent->val_.get(_name.data()).as<capnp::DynamicStruct>()};
+      _parent->val_.get({ _name.data(), _name.size() }).as<capnp::DynamicStruct>()};
 }
 
 Writer::OutputObjectType Writer::add_object_to_union(
@@ -142,7 +142,7 @@ Writer::OutputUnionType Writer::add_union_to_map(const std::string_view& _name,
 Writer::OutputUnionType Writer::add_union_to_object(
     const std::string_view& _name, OutputObjectType* _parent) const {
   return OutputUnionType{
-      _parent->val_.get(_name.data()).as<capnp::DynamicStruct>()};
+      _parent->val_.get({ _name.data(), _name.size() }).as<capnp::DynamicStruct>()};
 }
 
 Writer::OutputUnionType Writer::add_union_to_union(
@@ -171,7 +171,7 @@ Writer::OutputVarType Writer::add_null_to_map(const std::string_view& _name,
 
 Writer::OutputVarType Writer::add_null_to_object(
     const std::string_view& _name, OutputObjectType* _parent) const {
-  _parent->val_.set(_name.data(), capnp::VOID);
+  _parent->val_.set({ _name.data(), _name.size() }, capnp::VOID);
   return OutputVarType{};
 }
 
diff --git a/src/rfl/flexbuf/Writer.cpp b/src/rfl/flexbuf/Writer.cpp
index f635c8c3..afaf4538 100644
--- a/src/rfl/flexbuf/Writer.cpp
+++ b/src/rfl/flexbuf/Writer.cpp
@@ -51,7 +51,8 @@ Writer::OutputVarType Writer::add_null_to_array(
 
 Writer::OutputVarType Writer::add_null_to_object(
     const std::string_view& _name, OutputObjectType* /*_parent*/) const {
-  fbb_->Null(_name.data());
+  // Copy the string, because "std::string_view" might not be nullterminated.
+  fbb_->Null(std::string(_name).c_str());
   return OutputVarType{};
 }
 
@@ -64,7 +65,8 @@ void Writer::end_object(OutputObjectType* _obj) const {
 }
 
 Writer::OutputArrayType Writer::new_array(const std::string_view& _name) const {
-  const auto start = fbb_->StartVector(_name.data());
+  // Copy the string, because "std::string_view" might not be nullterminated.
+  const auto start = fbb_->StartVector(std::string(_name).c_str()); 
   return OutputArrayType{start};
 }
 
@@ -75,7 +77,8 @@ Writer::OutputArrayType Writer::new_array() const {
 
 Writer::OutputObjectType Writer::new_object(
     const std::string_view& _name) const {
-  const auto start = fbb_->StartMap(_name.data());
+  // Copy the string, because "std::string_view" might not be nullterminated.
+  const auto start = fbb_->StartMap(std::string(_name).c_str());
   return OutputObjectType{start};
 }
 
diff --git a/src/rfl/xml/Writer.cpp b/src/rfl/xml/Writer.cpp
index 0ae9d977..83be3cdc 100644
--- a/src/rfl/xml/Writer.cpp
+++ b/src/rfl/xml/Writer.cpp
@@ -39,27 +39,27 @@ Writer::~Writer() = default;
 
 Writer::OutputArrayType Writer::array_as_root(const size_t /*_size*/) const {
   auto node_child =
-      Ref<pugi::xml_node>::make(root_->append_child(root_name_.c_str()));
+      Ref<pugi::xml_node>::make(root_->append_child(root_name_));
   return OutputArrayType(root_name_, node_child);
 }
 
 Writer::OutputObjectType Writer::object_as_root(const size_t /*_size*/) const {
   auto node_child =
-      Ref<pugi::xml_node>::make(root_->append_child(root_name_.c_str()));
+      Ref<pugi::xml_node>::make(root_->append_child(root_name_));
   return OutputObjectType(node_child);
 }
 
 Writer::OutputVarType Writer::null_as_root() const {
   auto node_child =
-      Ref<pugi::xml_node>::make(root_->append_child(root_name_.c_str()));
+      Ref<pugi::xml_node>::make(root_->append_child(root_name_));
   return OutputVarType(node_child);
 }
 
 Writer::OutputVarType Writer::value_as_root_impl(
     const std::string& _str) const {
   auto node_child =
-      Ref<pugi::xml_node>::make(root_->append_child(root_name_.c_str()));
-  node_child->append_child(pugi::node_pcdata).set_value(_str.c_str());
+      Ref<pugi::xml_node>::make(root_->append_child(root_name_));
+  node_child->append_child(pugi::node_pcdata).set_value(_str);
   return OutputVarType(node_child);
 }
 
@@ -78,7 +78,7 @@ Writer::OutputVarType Writer::add_value_to_array_impl(
     const std::string& _str, OutputArrayType* _parent) const {
   auto node_child =
       Ref<pugi::xml_node>::make(_parent->node_->append_child(_parent->name_));
-  node_child->append_child(pugi::node_pcdata).set_value(_str.c_str());
+  node_child->append_child(pugi::node_pcdata).set_value(_str);
   return OutputVarType(node_child);
 }
 
@@ -86,15 +86,15 @@ Writer::OutputVarType Writer::add_value_to_object_impl(
     const std::string_view& _name, const std::string& _str,
     OutputObjectType* _parent, const bool _is_attribute) const {
   if (_is_attribute) {
-    _parent->node_->append_attribute(_name) = _str.c_str();
+    _parent->node_->append_attribute(_name) = _str;
     return OutputVarType(_parent->node_);
   } else if (_name == XML_CONTENT) {
-    _parent->node_->append_child(pugi::node_pcdata).set_value(_str.c_str());
+    _parent->node_->append_child(pugi::node_pcdata).set_value(_str);
     return OutputVarType(_parent->node_);
   } else {
     auto node_child =
         Ref<pugi::xml_node>::make(_parent->node_->append_child(_name));
-    node_child->append_child(pugi::node_pcdata).set_value(_str.c_str());
+    node_child->append_child(pugi::node_pcdata).set_value(_str);
     return OutputVarType(node_child);
   }
 }
diff --git a/src/rfl/yaml/Writer.cpp b/src/rfl/yaml/Writer.cpp
index e673e736..a45b144c 100644
--- a/src/rfl/yaml/Writer.cpp
+++ b/src/rfl/yaml/Writer.cpp
@@ -59,7 +59,7 @@ void Writer::end_object(OutputObjectType* /*_obj*/) const {
 }
 
 Writer::OutputArrayType Writer::new_array(const std::string_view& _name) const {
-  (*out_) << YAML::Key << _name.data() << YAML::Value << YAML::BeginSeq;
+  (*out_) << YAML::Key << std::string(_name) << YAML::Value << YAML::BeginSeq;
   return OutputArrayType{};
 }
 
@@ -70,7 +70,7 @@ Writer::OutputArrayType Writer::new_array() const {
 
 Writer::OutputObjectType Writer::new_object(
     const std::string_view& _name) const {
-  (*out_) << YAML::Key << _name.data() << YAML::Value << YAML::BeginMap;
+  (*out_) << YAML::Key << std::string(_name) << YAML::Value << YAML::BeginMap;
   return OutputObjectType{};
 }