diff --git a/include/byte.h b/include/gsl_byte.h
similarity index 100%
rename from include/byte.h
rename to include/gsl_byte.h
diff --git a/include/multi_span.h b/include/multi_span.h
index 3d00c6e..c4a0eac 100644
--- a/include/multi_span.h
+++ b/include/multi_span.h
@@ -21,7 +21,7 @@
 
 #include "gsl_assert.h"
 #include "gsl_util.h"
-#include "byte.h"
+#include "gsl_byte.h"
 #include <algorithm>
 #include <array>
 #include <cassert>
diff --git a/include/span.h b/include/span.h
index e52e14a..053b488 100644
--- a/include/span.h
+++ b/include/span.h
@@ -21,7 +21,7 @@
 
 #include "gsl_assert.h"
 #include "gsl_util.h"
-#include "byte.h"
+#include "gsl_byte.h"
 #include <array>
 #include <limits>
 #include <iterator>
@@ -154,18 +154,21 @@ struct is_allowed_element_type_conversion<From, const byte>
 };
 
 template <class Span>
-class span_iterator
-    : public std::iterator<std::random_access_iterator_tag, typename Span::element_type>
+class const_span_iterator
 {
-    using Base = std::iterator<std::random_access_iterator_tag, typename Span::element_type>;
-
 public:
-    using typename Base::reference;
-    using typename Base::pointer;
-    using typename Base::difference_type;
+    using iterator_category = std::random_access_iterator_tag;
+    using value_type = typename Span::element_type;
+    using difference_type = std::ptrdiff_t;
 
-    constexpr span_iterator() : span_iterator(nullptr, 0) {}
-    constexpr span_iterator(const Span* span, typename Span::index_type index) : span_(span), index_(index)
+    using const_pointer = std::add_const_t<value_type*>;
+    using pointer = const_pointer;
+
+    using const_reference = std::add_const_t<value_type&>;
+    using reference = const_reference;
+
+    constexpr const_span_iterator() : const_span_iterator(nullptr, 0) {}
+    constexpr const_span_iterator(const Span* span, typename Span::index_type index) : span_(span), index_(index)
     {
         Expects(span == nullptr || (index_ >= 0 && index <= span_->length()));
     }
@@ -173,59 +176,59 @@ public:
     constexpr reference operator*() const { Expects(span_); return (*span_)[index_]; }
     constexpr pointer operator->() const { Expects(span_); return &((*span_)[index_]); }
 
-    constexpr span_iterator& operator++() noexcept
+    constexpr const_span_iterator& operator++() noexcept
     {
         Expects(span_ && index_ >= 0 && index_ < span_->length());
         ++index_;
         return *this;
     }
 
-    constexpr span_iterator operator++(int) noexcept
+    constexpr const_span_iterator operator++(int) noexcept
     {
         auto ret = *this;
         ++(*this);
         return ret;
     }
 
-    constexpr span_iterator& operator--() noexcept
+    constexpr const_span_iterator& operator--() noexcept
     {
         Expects(span_ && index > 0 && index_ <= span_->length());
         --index_;
         return *this;
     }
 
-    constexpr span_iterator operator--(int) noexcept
+    constexpr const_span_iterator operator--(int) noexcept
     {
         auto ret = *this;
         --(*this);
         return ret;
     }
 
-    constexpr span_iterator operator+(difference_type n) const noexcept
+    constexpr const_span_iterator operator+(difference_type n) const noexcept
     {
         auto ret{*this};
         return ret += n;
     }
 
-    constexpr span_iterator& operator+=(difference_type n) noexcept
+    constexpr const_span_iterator& operator+=(difference_type n) noexcept
     {
         index_ += n;
         Expects(span_ && index_ >= 0 && index_ <= span_->length());
         return *this;
     }
 
-    constexpr span_iterator operator-(difference_type n) const noexcept
+    constexpr const_span_iterator operator-(difference_type n) const noexcept
     {
         auto ret{*this};
         return ret -= n;
     }
 
-    constexpr span_iterator& operator-=(difference_type n) noexcept
+    constexpr const_span_iterator& operator-=(difference_type n) noexcept
     {
         return *this += -n;
     }
 
-    constexpr difference_type operator-(const span_iterator& rhs) const noexcept
+    constexpr difference_type operator-(const const_span_iterator& rhs) const noexcept
     {
         Expects(span_ == rhs.span_);
         return index_ - rhs.index_;
@@ -236,26 +239,26 @@ public:
         return *(*this + n);
     }
 
-    constexpr bool operator==(const span_iterator& rhs) const noexcept
+    constexpr bool operator==(const const_span_iterator& rhs) const noexcept
     {
         return span_ == rhs.span_ && index_ == rhs.index_;
     }
 
-    constexpr bool operator!=(const span_iterator& rhs) const noexcept { return !(*this == rhs); }
+    constexpr bool operator!=(const const_span_iterator& rhs) const noexcept { return !(*this == rhs); }
 
-    constexpr bool operator<(const span_iterator& rhs) const noexcept
+    constexpr bool operator<(const const_span_iterator& rhs) const noexcept
     {
         Expects(span_ == rhs.span_);
         return index_ < rhs.index_;
     }
 
-    constexpr bool operator<=(const span_iterator& rhs) const noexcept { return !(rhs < *this); }
+    constexpr bool operator<=(const const_span_iterator& rhs) const noexcept { return !(rhs < *this); }
 
-    constexpr bool operator>(const span_iterator& rhs) const noexcept { return rhs < *this; }
+    constexpr bool operator>(const const_span_iterator& rhs) const noexcept { return rhs < *this; }
 
-    constexpr bool operator>=(const span_iterator& rhs) const noexcept { return !(rhs > *this); }
+    constexpr bool operator>=(const const_span_iterator& rhs) const noexcept { return !(rhs > *this); }
 
-    void swap(span_iterator& rhs) noexcept
+    void swap(const_span_iterator& rhs) noexcept
     {
         std::swap(index_, rhs.index_);
         std::swap(m_span, rhs.m_span);
@@ -266,6 +269,75 @@ private:
     ptrdiff_t index_;
 };
 
+
+template <class Span>
+class span_iterator : public const_span_iterator<Span>
+{
+    using base_type = const_span_iterator<Span>;
+
+public:
+    using iterator_category = std::random_access_iterator_tag;
+    using value_type = typename Span::element_type;
+    using difference_type = std::ptrdiff_t;
+
+    using pointer = value_type*;
+    using reference = value_type&;
+
+    constexpr span_iterator() : base_type() {}
+    constexpr span_iterator(const Span* span, typename Span::index_type index) : base_type(span, index) {}
+
+    constexpr reference operator*() const { return reinterpret_cast<reference>(base_type::operator*()); }
+    constexpr pointer operator->() const { return reinterpret_cast<pointer>(base_type::operator->()); }
+
+    constexpr span_iterator& operator++() noexcept { base_type::operator++(); return *this; }
+
+    constexpr span_iterator operator++(int) noexcept { return base_type::operator++(1); }
+
+    constexpr span_iterator& operator--() noexcept { base_type::operator--(); return *this; }
+
+    constexpr span_iterator operator--(int) noexcept { return base_type::operator--(1); }
+
+    constexpr span_iterator operator+(difference_type n) const noexcept { return base_type::operator+(n); }
+
+    constexpr span_iterator& operator+=(difference_type n) noexcept { return base_type::operator+=(n); }
+
+    constexpr span_iterator operator-(difference_type n) const noexcept { return base_type::operator-(n); }
+
+    constexpr span_iterator& operator-=(difference_type n) noexcept { return base_type::operator-=(n); }
+
+    constexpr difference_type operator-(const span_iterator& rhs) const noexcept { return base_type::operator-(rhs); }
+
+    constexpr reference operator[](difference_type n) const noexcept { return *(*this + n); }
+
+    constexpr bool operator==(const span_iterator& rhs) const noexcept { return base_type::operator==(rhs); }
+
+    constexpr bool operator!=(const span_iterator& rhs) const noexcept { return !(*this == rhs); }
+
+    constexpr bool operator<(const span_iterator& rhs) const noexcept { return base_type::operator<(rhs); }
+
+    constexpr bool operator<=(const span_iterator& rhs) const noexcept { return !(rhs < *this); }
+
+    constexpr bool operator>(const span_iterator& rhs) const noexcept { return rhs < *this; }
+
+    constexpr bool operator>=(const span_iterator& rhs) const noexcept { return !(rhs > *this); }
+
+    void swap(span_iterator& rhs) noexcept { base_type::swap(rhs); }
+};
+
+template <typename Span>
+constexpr const_span_iterator<Span> operator+(typename const_span_iterator<Span>::difference_type n,
+    const const_span_iterator<Span>& rhs) noexcept
+{
+    return rhs + n;
+}
+
+template <typename Span>
+constexpr const_span_iterator<Span> operator-(typename const_span_iterator<Span>::difference_type n,
+    const const_span_iterator<Span>& rhs) noexcept
+{
+    return rhs - n;
+}
+
 template <typename Span>
 constexpr span_iterator<Span> operator+(typename span_iterator<Span>::difference_type n,
     const span_iterator<Span>& rhs) noexcept
@@ -294,7 +366,9 @@ public:
     using reference = element_type&;
 
     using iterator = details::span_iterator<span<ElementType, Extent>>;
+    using const_iterator = details::span_iterator<span>;
     using reverse_iterator = std::reverse_iterator<iterator>;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
     constexpr static const index_type extent = Extent;
 
diff --git a/include/string_span.h b/include/string_span.h
index 69c3a81..8aba362 100644
--- a/include/string_span.h
+++ b/include/string_span.h
@@ -21,7 +21,7 @@
 
 #include "gsl_assert.h"
 #include "gsl_util.h"
-#include "multi_span.h"
+#include "span.h"
 #include <cstring>
 #include <string>
 
@@ -72,19 +72,19 @@ namespace gsl
 // (sometimes needlessly) break existing programs when introduced.
 //
 
-template<typename CharT, std::ptrdiff_t Extent = dynamic_range>
+template<typename CharT, std::ptrdiff_t Extent = dynamic_extent>
 using basic_zstring = CharT*;
 
-template<std::ptrdiff_t Extent = dynamic_range>
+template<std::ptrdiff_t Extent = dynamic_extent>
 using czstring = basic_zstring<const char, Extent>;
 
-template<std::ptrdiff_t Extent = dynamic_range>
+template<std::ptrdiff_t Extent = dynamic_extent>
 using cwzstring = basic_zstring<const wchar_t, Extent>;
 
-template<std::ptrdiff_t Extent = dynamic_range>
+template<std::ptrdiff_t Extent = dynamic_extent>
 using zstring = basic_zstring<char, Extent>;
 
-template<std::ptrdiff_t Extent = dynamic_range>
+template<std::ptrdiff_t Extent = dynamic_extent>
 using wzstring = basic_zstring<wchar_t, Extent>;
 
 //
@@ -96,7 +96,7 @@ using wzstring = basic_zstring<wchar_t, Extent>;
 // Will fail-fast if sentinel cannot be found before max elements are examined.
 //
 template<typename T, const T Sentinel>
-multi_span<T, dynamic_range> ensure_sentinel(T* seq, std::ptrdiff_t max = PTRDIFF_MAX)
+span<T, dynamic_extent> ensure_sentinel(T* seq, std::ptrdiff_t max = PTRDIFF_MAX)
 {
     auto cur = seq;
     while ((cur - seq) < max && *cur != Sentinel) ++cur;
@@ -111,34 +111,34 @@ multi_span<T, dynamic_range> ensure_sentinel(T* seq, std::ptrdiff_t max = PTRDIF
 // the limit of size_type.
 //
 template<typename T>
-inline multi_span<T, dynamic_range> ensure_z(T* const & sz, std::ptrdiff_t max = PTRDIFF_MAX)
+inline span<T, dynamic_extent> ensure_z(T* const & sz, std::ptrdiff_t max = PTRDIFF_MAX)
 {
     return ensure_sentinel<T, 0>(sz, max);
 }
 
 // TODO (neilmac) there is probably a better template-magic way to get the const and non-const overloads to share an implementation
-inline multi_span<char, dynamic_range> ensure_z(char* const& sz, std::ptrdiff_t max)
+inline span<char, dynamic_extent> ensure_z(char* const& sz, std::ptrdiff_t max)
 {
     auto len = strnlen(sz, narrow_cast<size_t>(max));
     Ensures(sz[len] == 0);
     return{ sz, static_cast<std::ptrdiff_t>(len) };
 }
 
-inline multi_span<const char, dynamic_range> ensure_z(const char* const& sz, std::ptrdiff_t max)
+inline span<const char, dynamic_extent> ensure_z(const char* const& sz, std::ptrdiff_t max)
 {
     auto len = strnlen(sz, narrow_cast<size_t>(max));
     Ensures(sz[len] == 0);
     return{ sz, static_cast<std::ptrdiff_t>(len) };
 }
 
-inline multi_span<wchar_t, dynamic_range> ensure_z(wchar_t* const& sz, std::ptrdiff_t max)
+inline span<wchar_t, dynamic_extent> ensure_z(wchar_t* const& sz, std::ptrdiff_t max)
 {
     auto len = wcsnlen(sz, narrow_cast<size_t>(max));
     Ensures(sz[len] == 0);
     return{ sz, static_cast<std::ptrdiff_t>(len) };
 }
 
-inline multi_span<const wchar_t, dynamic_range> ensure_z(const wchar_t* const& sz, std::ptrdiff_t max)
+inline span<const wchar_t, dynamic_extent> ensure_z(const wchar_t* const& sz, std::ptrdiff_t max)
 {
     auto len = wcsnlen(sz, narrow_cast<size_t>(max));
     Ensures(sz[len] == 0);
@@ -146,10 +146,10 @@ inline multi_span<const wchar_t, dynamic_range> ensure_z(const wchar_t* const& s
 }
 
 template<typename T, size_t N>
-multi_span<T, dynamic_range> ensure_z(T(&sz)[N]) { return ensure_z(&sz[0], static_cast<std::ptrdiff_t>(N)); }
+span<T, dynamic_extent> ensure_z(T(&sz)[N]) { return ensure_z(&sz[0], static_cast<std::ptrdiff_t>(N)); }
 
 template<class Cont>
-multi_span<typename std::remove_pointer<typename Cont::pointer>::type, dynamic_range> ensure_z(Cont& cont)
+span<typename std::remove_pointer<typename Cont::pointer>::type, dynamic_extent> ensure_z(Cont& cont)
 {
     return ensure_z(cont.data(), static_cast<std::ptrdiff_t>(cont.length()));
 }
@@ -216,9 +216,7 @@ namespace details
 //
 // string_span and relatives
 //
-// Note that Extent is always single-dimension only
-//
-template <typename CharT, std::ptrdiff_t Extent = dynamic_range>
+template <typename CharT, std::ptrdiff_t Extent = dynamic_extent>
 class basic_string_span
 {
 public:
@@ -227,8 +225,7 @@ public:
     using pointer = std::add_pointer_t<value_type>;
     using reference = std::add_lvalue_reference_t<value_type>;
     using const_reference = std::add_lvalue_reference_t<const_value_type>;
-    using bounds_type = static_bounds<Extent>;
-    using impl_type = multi_span<value_type, Extent>;
+    using impl_type = span<value_type, Extent>;
 
     using size_type = ptrdiff_t;
     using iterator = typename impl_type::iterator;
@@ -296,52 +293,52 @@ public:
     {}
 
     // from containers. Containers must have .size() and .data() function signatures
-    template <typename Cont, typename DataType = typename Cont::value_type,
-        typename Dummy = std::enable_if_t<!details::is_multi_span<Cont>::value
-        && !details::is_basic_string_span<Cont>::value
-        && !(!std::is_const<value_type>::value && std::is_const<Cont>::value) // no converting const containers to non-const span
-        && std::is_convertible<DataType*, value_type*>::value
-        && std::is_same<std::decay_t<decltype(std::declval<Cont>().size(), *std::declval<Cont>().data())>, DataType>::value>
+    template <typename Cont,
+        typename = std::enable_if_t<
+        !details::is_basic_string_span<Cont>::value
+        && !details::is_span<Cont>::value
+        && std::is_convertible<Cont::pointer, pointer>::value
+        && std::is_convertible<Cont::pointer, decltype(std::declval<Cont>().data())>::value>
     >
-    constexpr basic_string_span(Cont& cont)
-        : span_(cont.data(), cont.size())
-    {}
+    constexpr basic_string_span(Cont& cont) : span_(cont.data(), cont.size()) {}
 
     // disallow creation from temporary containers and strings
-    template <typename Cont, typename DataType = typename Cont::value_type,
-        typename Dummy = std::enable_if_t<!details::is_multi_span<Cont>::value
-        && !details::is_basic_string_span<Cont>::value
-        && std::is_convertible<DataType*, value_type*>::value
-        && std::is_same<std::decay_t<decltype(std::declval<Cont>().size(), *std::declval<Cont>().data())>, DataType>::value>
-    >
-    basic_string_span(Cont&& cont) = delete;
+    template <typename Cont,
+        typename = std::enable_if_t<
+        !details::is_basic_string_span<Cont>::value
+        && !details::is_span<Cont>::value
+        && std::is_convertible<Cont::pointer, pointer>::value
+        && std::is_convertible<Cont::pointer, decltype(std::declval<Cont>().data())>::value>
+        >
+    constexpr basic_string_span(const Cont& cont) : span_(cont.data(), cont.size()) {}
 
 #ifndef GSL_MSVC_HAS_SFINAE_SUBSTITUTION_ICE
     // from span
     template <typename OtherValueType, std::ptrdiff_t OtherExtent,
         typename Dummy = std::enable_if_t<
-        std::is_convertible<OtherValueType*, value_type*>::value
-        && std::is_convertible<static_bounds<OtherExtent>, bounds_type>::value>
+        std::is_convertible<span<OtherValueType, OtherExtent>, impl_type>::value
+        >
     >
-    constexpr basic_string_span(multi_span<OtherValueType, OtherExtent> other) noexcept
+    constexpr basic_string_span(span<OtherValueType, OtherExtent> other) noexcept
         : span_(other)
     {}
 #else
     // from span
-    constexpr basic_string_span(multi_span<value_type, Extent> other) noexcept
+    constexpr basic_string_span(span<value_type, Extent> other) noexcept
         : span_(other)
     {}
         
-    template <typename Dummy = std::enable_if_t<!std::is_same<std::remove_const_t<value_type>, value_type>::value>>
-    constexpr basic_string_span(multi_span<std::remove_const_t<value_type>, Extent> other) noexcept
+    template <typename = std::enable_if_t<!std::is_same<std::remove_const_t<value_type>, value_type>::value>>
+    constexpr basic_string_span(span<std::remove_const_t<value_type>, Extent> other) noexcept
         : span_(other)
     {}
 #endif
 
     // from string_span
     template <typename OtherValueType, std::ptrdiff_t OtherExtent,
-        typename OtherBounds = static_bounds<OtherExtent>,
-        typename Dummy = std::enable_if_t<std::is_convertible<OtherValueType*, value_type*>::value && std::is_convertible<OtherBounds, bounds_type>::value>
+        typename = std::enable_if_t<
+            std::is_convertible<basic_string_span<OtherValueType, OtherExtent>::impl_type, impl_type>::value
+        >
     >
     constexpr basic_string_span(basic_string_span<OtherValueType, OtherExtent> other) noexcept
         : span_(other.data(), other.length())
@@ -359,7 +356,7 @@ public:
         return{ span_.template first<Count>() };
     }
 
-    constexpr basic_string_span<value_type, dynamic_range> first(size_type count) const noexcept
+    constexpr basic_string_span<value_type, dynamic_extent> first(size_type count) const noexcept
     {
         return{ span_.first(count) };
     }
@@ -371,7 +368,7 @@ public:
         return{ span_.template last<Count>() };
     }
 
-    constexpr basic_string_span<value_type, dynamic_range> last(size_type count) const noexcept
+    constexpr basic_string_span<value_type, dynamic_extent> last(size_type count) const noexcept
     {
         return{ span_.last(count) };
     }
@@ -383,7 +380,7 @@ public:
         return{ span_.template subspan<Offset, Count>() };
     }
 
-    constexpr basic_string_span<value_type, dynamic_range> subspan(size_type offset, size_type count = dynamic_range) const noexcept
+    constexpr basic_string_span<value_type, dynamic_extent> subspan(size_type offset, size_type count = dynamic_extent) const noexcept
     {
         return{ span_.subspan(offset, count) };
     }
@@ -478,16 +475,16 @@ private:
     impl_type span_;
 };
 
-template<std::ptrdiff_t Extent = dynamic_range>
+template<std::ptrdiff_t Extent = dynamic_extent>
 using string_span = basic_string_span<char, Extent>;
 
-template<std::ptrdiff_t Extent = dynamic_range>
+template<std::ptrdiff_t Extent = dynamic_extent>
 using cstring_span = basic_string_span<const char, Extent>;
 
-template<std::ptrdiff_t Extent = dynamic_range>
+template<std::ptrdiff_t Extent = dynamic_extent>
 using wstring_span = basic_string_span<wchar_t, Extent>;
 
-template<std::ptrdiff_t Extent = dynamic_range>
+template<std::ptrdiff_t Extent = dynamic_extent>
 using cwstring_span = basic_string_span<const wchar_t, Extent>;
 
 //
@@ -527,7 +524,7 @@ inline std::wstring to_string(wstring_span<> view)
 
 // zero-terminated string span, used to convert
 // zero-terminated spans to legacy strings
-template<typename CharT, std::ptrdiff_t Extent = dynamic_range>
+template<typename CharT, std::ptrdiff_t Extent = dynamic_extent>
 class basic_zstring_span
 {
 public:
@@ -540,14 +537,14 @@ public:
     using zstring_type = basic_zstring<value_type, Extent>;
     using const_zstring_type = basic_zstring<const_value_type, Extent>;
 
-    using impl_type = multi_span<value_type, Extent>;
+    using impl_type = span<value_type, Extent>;
     using string_span_type = basic_string_span<value_type, Extent>;
 
-    constexpr basic_zstring_span(impl_type multi_span) noexcept
-        : span_(multi_span)
+    constexpr basic_zstring_span(impl_type s) noexcept
+        : span_(s)
     {
         // expects a zero-terminated span
-        Expects(multi_span[multi_span.size() - 1] == '\0');
+        Expects(s[s.size() - 1] == '\0');
     }
 
     // copy
@@ -588,22 +585,22 @@ private:
     impl_type span_;
 };
 
-template <std::ptrdiff_t Max = dynamic_range>
+template <std::ptrdiff_t Max = dynamic_extent>
 using zstring_span = basic_zstring_span<char, Max>;
 
-template <std::ptrdiff_t Max = dynamic_range>
+template <std::ptrdiff_t Max = dynamic_extent>
 using wzstring_span = basic_zstring_span<wchar_t, Max>;
 
-template <std::ptrdiff_t Max = dynamic_range>
+template <std::ptrdiff_t Max = dynamic_extent>
 using czstring_span = basic_zstring_span<const char, Max>;
 
-template <std::ptrdiff_t Max = dynamic_range>
+template <std::ptrdiff_t Max = dynamic_extent>
 using cwzstring_span = basic_zstring_span<const wchar_t, Max>;
 
 } // namespace GSL
 
 // operator ==
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>
 >
@@ -617,7 +614,7 @@ bool operator==(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
 #endif
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename Dummy = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value
     && !gsl::details::is_basic_string_span<T>::value>
@@ -637,10 +634,10 @@ bool operator==(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 // VS treats temp and const containers as convertible to basic_string_span,
 // so the cases below are already covered by the previous operators
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -651,10 +648,10 @@ bool operator==(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
     return std::equal(one.begin(), one.end(), tmp.begin(), tmp.end());
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -667,7 +664,7 @@ bool operator==(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 #endif
 
 // operator !=
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>
 >
@@ -676,7 +673,7 @@ bool operator!=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
     return !(one == other);
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename Dummy = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value
     && !gsl::details::is_basic_string_span<T>::value>
@@ -691,10 +688,10 @@ bool operator!=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 // VS treats temp and const containers as convertible to basic_string_span,
 // so the cases below are already covered by the previous operators
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -704,10 +701,10 @@ bool operator!=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
     return !(one == other);
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -719,7 +716,7 @@ bool operator!=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 #endif
 
 // operator<
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>
 >
@@ -729,7 +726,7 @@ bool operator<(gsl::basic_string_span<CharT, Extent> one, const T& other) noexce
     return std::lexicographical_compare(one.begin(), one.end(), tmp.begin(), tmp.end());
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename Dummy = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value
     && !gsl::details::is_basic_string_span<T>::value>
@@ -745,10 +742,10 @@ bool operator<(const T& one, gsl::basic_string_span<CharT, Extent> other) noexce
 // VS treats temp and const containers as convertible to basic_string_span,
 // so the cases below are already covered by the previous operators
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -759,10 +756,10 @@ bool operator<(gsl::basic_string_span<CharT, Extent> one, const T& other) noexce
     return std::lexicographical_compare(one.begin(), one.end(), tmp.begin(), tmp.end());
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -775,7 +772,7 @@ bool operator<(const T& one, gsl::basic_string_span<CharT, Extent> other) noexce
 #endif
 
 // operator <=
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>
 >
@@ -784,7 +781,7 @@ bool operator<=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
     return !(other < one);
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename Dummy = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value
     && !gsl::details::is_basic_string_span<T>::value>
@@ -799,10 +796,10 @@ bool operator<=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 // VS treats temp and const containers as convertible to basic_string_span,
 // so the cases below are already covered by the previous operators
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -812,10 +809,10 @@ bool operator<=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
     return !(other < one);
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -827,7 +824,7 @@ bool operator<=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 #endif
 
 // operator>
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>
 >
@@ -836,7 +833,7 @@ bool operator>(gsl::basic_string_span<CharT, Extent> one, const T& other) noexce
     return other < one;
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename Dummy = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value
     && !gsl::details::is_basic_string_span<T>::value>
@@ -851,10 +848,10 @@ bool operator>(const T& one, gsl::basic_string_span<CharT, Extent> other) noexce
 // VS treats temp and const containers as convertible to basic_string_span,
 // so the cases below are already covered by the previous operators
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -864,10 +861,10 @@ bool operator>(gsl::basic_string_span<CharT, Extent> one, const T& other) noexce
     return other < one;
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -879,7 +876,7 @@ bool operator>(const T& one, gsl::basic_string_span<CharT, Extent> other) noexce
 #endif
 
 // operator >=
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>
 >
@@ -888,7 +885,7 @@ bool operator>=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
     return !(one < other);
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename Dummy = std::enable_if_t<
     std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value
     && !gsl::details::is_basic_string_span<T>::value>
@@ -903,10 +900,10 @@ bool operator>=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 // VS treats temp and const containers as convertible to basic_string_span,
 // so the cases below are already covered by the previous operators
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -916,10 +913,10 @@ bool operator>=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
     return !(one < other);
 }
 
-template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_multi_span<T>::value
+    !gsl::details::is_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
diff --git a/tests/byte_tests.cpp b/tests/byte_tests.cpp
index ff91e50..19456fd 100644
--- a/tests/byte_tests.cpp
+++ b/tests/byte_tests.cpp
@@ -15,7 +15,7 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 #include <UnitTest++/UnitTest++.h>
-#include <byte.h>
+#include <gsl_byte.h>
 
 #include <iostream>
 #include <list>
diff --git a/tests/string_span_tests.cpp b/tests/string_span_tests.cpp
index 6876253..f380be3 100644
--- a/tests/string_span_tests.cpp
+++ b/tests/string_span_tests.cpp
@@ -142,7 +142,7 @@ SUITE(string_span_tests)
             const char* ptr = "Hello";
             const std::string str = "Hello";
             const std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
-            gsl::multi_span<const char> sp = ensure_z("Hello");
+            gsl::span<const char> sp = ensure_z("Hello");
 
             // comparison to  literal
             CHECK(span == cstring_span<>("Hello"));
@@ -182,7 +182,7 @@ SUITE(string_span_tests)
             char* ptr = ar;
             std::string str = "Hello";
             std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
-            gsl::multi_span<char> sp = ensure_z(ar1);
+            gsl::span<char> sp = ensure_z(ar1);
 
             // comparison to static array with no null termination
             CHECK(span == string_span<>(ar));
@@ -216,7 +216,7 @@ SUITE(string_span_tests)
             const char ar2[10] = "Hello";
             const std::string str = "Hello";
             const std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
-            gsl::multi_span<const char> sp = ensure_z("Hello");
+            gsl::span<const char> sp = ensure_z("Hello");
 
             cstring_span<> span = "Hello";
 
@@ -253,7 +253,7 @@ SUITE(string_span_tests)
             char* _ptr = _ar;
             std::string _str = "Hello";
             std::vector<char> _vec = { 'H', 'e', 'l', 'l', 'o' };
-            gsl::multi_span<char> _sp{ _ar, 5 };
+            gsl::span<char> _sp{ _ar, 5 };
 
             CHECK(span == _ar);
             CHECK(span == _ar1);
@@ -447,7 +447,7 @@ SUITE(string_span_tests)
 
         // from span of a final extent
         {
-            multi_span<const char, 6> sp = "Hello";
+            span<const char, 6> sp = "Hello";
             cstring_span<> span = sp;
             CHECK(span.length() == 6);
         }
@@ -455,7 +455,7 @@ SUITE(string_span_tests)
         // from const span of a final extent to non-const string_span
 #ifdef CONFIRM_COMPILATION_ERRORS
         {
-            multi_span<const char, 6> sp = "Hello";
+            span<const char, 6> sp = "Hello";
             string_span<> span = sp;
             CHECK(span.length() == 6);
         }
@@ -568,7 +568,7 @@ SUITE(string_span_tests)
         // from const span
         {
             std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
-            const multi_span<const char> inner = vec;
+            const span<const char> inner = vec;
             cstring_span<> span = inner;
             CHECK(span.length() == 5);
         }
@@ -576,7 +576,7 @@ SUITE(string_span_tests)
         // from non-const span
         {
             std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
-            multi_span<char> inner = vec;
+            span<char> inner = vec;
             cstring_span<> span = inner;
             CHECK(span.length() == 5);
         }
@@ -675,7 +675,7 @@ SUITE(string_span_tests)
         {
 #ifdef CONFIRM_COMPILATION_ERRORS
             std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
-            const multi_span<const char> inner = vec;
+            const span<const char> inner = vec;
             string_span<> span = inner;
             CHECK(span.length() == 5);
 #endif
@@ -684,7 +684,7 @@ SUITE(string_span_tests)
         // from non-const span
         {
             std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
-            multi_span<char> inner = vec;
+            span<char> inner = vec;
             string_span<> span = inner;
             CHECK(span.length() == 5);
         }
@@ -693,7 +693,7 @@ SUITE(string_span_tests)
         {
 #ifdef CONFIRM_COMPILATION_ERRORS
             const std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
-            const multi_span<char> inner = vec;
+            const span<char> inner = vec;
             string_span<> span = inner;
             CHECK(span.length() == 5);
 #endif
@@ -746,7 +746,7 @@ SUITE(string_span_tests)
     T create() { return T{}; }
 
     template <class T>
-    void use(basic_string_span<T, gsl::dynamic_range> s) {}
+    void use(basic_string_span<T, gsl::dynamic_extent> s) {}
 
     TEST(MoveConstructors)
     {
@@ -769,12 +769,12 @@ SUITE(string_span_tests)
 
         // move span
         {
-            multi_span<const char> span = ensure_z("Hello");
+            span<const char> span = ensure_z("Hello");
             cstring_span<> span1 = std::move(span);
             CHECK(span1.length() == 5);
         }
         {
-            multi_span<const char> span = ensure_z("Hello");
+            span<const char> span = ensure_z("Hello");
             cstring_span<> span2 = move_wrapper(std::move(span));
             CHECK(span2.length() == 5);
         }