diff --git a/include/boost/url/detail/impl/any_path_iter.ipp b/include/boost/url/detail/impl/any_path_iter.ipp
index 3ad9c651..42fa4fcf 100644
--- a/include/boost/url/detail/impl/any_path_iter.ipp
+++ b/include/boost/url/detail/impl/any_path_iter.ipp
@@ -75,10 +75,13 @@ measure(
     if(! p_)
         return false;
     string_view s(p_, n_);
-    urls::validate_pct_encoding(
-        s, ec, pchars, {});
-    if(ec.failed())
+    auto rn = urls::validate_pct_encoding(
+        s, pchars, {});
+    if( !rn )
+    {
+        ec = rn.error();
         return false;
+    }
     n += s.size();
     increment();
     return true;
@@ -266,10 +269,13 @@ measure_impl(
     std::size_t& n,
     error_code& ec) noexcept
 {
-    urls::validate_pct_encoding(
-        s, ec, pchars, {});
-    if(ec.failed())
+    auto rn = urls::validate_pct_encoding(
+        s, pchars, {});
+    if( !rn )
+    {
+        ec = rn.error();
         return false;
+    }
     n += s.size();
     return true;
 }
diff --git a/include/boost/url/detail/impl/any_query_iter.ipp b/include/boost/url/detail/impl/any_query_iter.ipp
index 33d4b130..85b3ab33 100644
--- a/include/boost/url/detail/impl/any_query_iter.ipp
+++ b/include/boost/url/detail/impl/any_query_iter.ipp
@@ -71,10 +71,13 @@ measure(
     if(! p_)
         return false;
     string_view s(p_, n_);
-    urls::validate_pct_encoding(
-        s, ec, query_chars, {});
-    if(ec.failed())
+    auto rn = urls::validate_pct_encoding(
+        s, query_chars, {});
+    if( !rn )
+    {
+        ec = rn.error();
         return false;
+    }
     n += s.size();
     increment();
     return true;
@@ -261,20 +264,26 @@ measure_impl(
 {
     pct_decode_opts opt;
     opt.plus_to_space = true;
-    validate_pct_encoding(
-        key, ec, query_chars, opt);
-    if(ec.failed())
+    auto rn = validate_pct_encoding(
+        key, query_chars, opt);
+    if( !rn )
+    {
+        ec = rn.error();
         return false;
+    }
     n += key.size();
     if(value)
     {
-        validate_pct_encoding(
-            *value, ec, query_chars, opt);
-        if(ec.failed())
+        rn = validate_pct_encoding(
+            *value, query_chars, opt);
+        if( !rn )
+        {
+            ec = rn.error();
             return false;
+        }
         n += 1 + value->size();
     }
-    return ! ec.failed();
+    return !  !rn ;
 }
 
 void
diff --git a/include/boost/url/detail/impl/segments_encoded_iterator_impl.ipp b/include/boost/url/detail/impl/segments_encoded_iterator_impl.ipp
index e7340e40..a50f6920 100644
--- a/include/boost/url/detail/impl/segments_encoded_iterator_impl.ipp
+++ b/include/boost/url/detail/impl/segments_encoded_iterator_impl.ipp
@@ -73,7 +73,7 @@ increment() noexcept
     auto rv = grammar::parse(
         next_, end_,
             detail::slash_segment_rule);
-    if(rv.has_error())
+    if( !rv )
     {
         next_ = nullptr;
         return;
diff --git a/include/boost/url/detail/impl/segments_iterator_impl.ipp b/include/boost/url/detail/impl/segments_iterator_impl.ipp
index 1b937c95..79eb5b0a 100644
--- a/include/boost/url/detail/impl/segments_iterator_impl.ipp
+++ b/include/boost/url/detail/impl/segments_iterator_impl.ipp
@@ -77,7 +77,7 @@ increment() noexcept
     auto rv = grammar::parse(
         next_, end_,
             detail::slash_segment_rule);
-    if(rv.has_error())
+    if( !rv )
     {
         next_ = nullptr;
         return;
diff --git a/include/boost/url/error_type.hpp b/include/boost/url/error_type.hpp
index 27f520c7..6e55bb10 100644
--- a/include/boost/url/error_type.hpp
+++ b/include/boost/url/error_type.hpp
@@ -107,7 +107,7 @@ namespace errc = boost::system::errc;
     @code
     result< url_view > r = parse_uri( "http://example.com/path/to/file.txt" );
 
-    if( r.has_error() )
+    if( !r )
         std::cout << r.error();
     else
         std::cout << r.value();
diff --git a/include/boost/url/grammar/impl/not_empty_rule.hpp b/include/boost/url/grammar/impl/not_empty_rule.hpp
index d53dd6bc..ee498d4f 100644
--- a/include/boost/url/grammar/impl/not_empty_rule.hpp
+++ b/include/boost/url/grammar/impl/not_empty_rule.hpp
@@ -33,7 +33,7 @@ parse(
     }
     auto const it0 = it;
     auto rv = r_.parse(it, end);
-    if( rv.has_error())
+    if(  !rv )
     {
         // error
         return rv;
diff --git a/include/boost/url/grammar/impl/optional_rule.hpp b/include/boost/url/grammar/impl/optional_rule.hpp
index 29d97910..57203b9c 100644
--- a/include/boost/url/grammar/impl/optional_rule.hpp
+++ b/include/boost/url/grammar/impl/optional_rule.hpp
@@ -28,7 +28,7 @@ parse(
         return boost::none;
     auto const it0 = it;
     auto rv = r_.parse(it, end);
-    if(! rv.has_error())
+    if(rv)
         return value_type(*rv);
     it = it0;
     return boost::none;
diff --git a/include/boost/url/grammar/impl/parse.hpp b/include/boost/url/grammar/impl/parse.hpp
index 9a4875cf..2aaa78e9 100644
--- a/include/boost/url/grammar/impl/parse.hpp
+++ b/include/boost/url/grammar/impl/parse.hpp
@@ -54,8 +54,8 @@ parse(
     auto it = s.data();
     auto const end = it + s.size();
     auto rv = r.parse(it, end);
-    if( rv.has_value() &&
-            it != end)
+    if( rv &&
+        it != end)
         return error::leftover;
     return rv;
 }
diff --git a/include/boost/url/grammar/impl/range_rule.hpp b/include/boost/url/grammar/impl/range_rule.hpp
index dc010bf0..d4a392f1 100644
--- a/include/boost/url/grammar/impl/range_rule.hpp
+++ b/include/boost/url/grammar/impl/range_rule.hpp
@@ -364,7 +364,7 @@ public:
             r_->s_.data() +
             r_->s_.size();
         rv_ = r_->get().next(p_, end);
-        if(rv_.has_error())
+        if( !rv_ )
             p_ = nullptr;
         return *this;
     }
@@ -393,7 +393,7 @@ private:
             r_->s_.data() +
             r_->s_.size();
         rv_ = r_->get().first(p_, end);
-        if(rv_.has_error())
+        if( !rv_ )
             p_ = nullptr;
     }
 
@@ -533,7 +533,7 @@ parse(
     auto it1 = it;
     auto rv = (grammar::parse)(
         it, end, next_);
-    if(rv.has_error())
+    if( !rv )
     {
         if(rv.error() != error::range_end)
         {
@@ -557,7 +557,7 @@ parse(
         it1 = it;
         rv = (grammar::parse)(
             it, end, next_);
-        if(rv.has_error())
+        if( !rv )
         {
             if(rv.error() != error::range_end)
             {
@@ -603,7 +603,7 @@ parse(
     auto it1 = it;
     auto rv = (grammar::parse)(
         it, end, first_);
-    if(rv.has_error())
+    if( !rv )
     {
         if(rv.error() != error::range_end)
         {
@@ -627,7 +627,7 @@ parse(
         it1 = it;
         rv = (grammar::parse)(
             it, end, next_);
-        if(rv.has_error())
+        if( !rv )
         {
             if(rv.error() != error::range_end)
             {
diff --git a/include/boost/url/grammar/impl/tuple_rule.hpp b/include/boost/url/grammar/impl/tuple_rule.hpp
index 2002cdfe..1605ac32 100644
--- a/include/boost/url/grammar/impl/tuple_rule.hpp
+++ b/include/boost/url/grammar/impl/tuple_rule.hpp
@@ -80,7 +80,7 @@ struct parse_sequence
         result<void> rv =
             grammar::parse(
                 it, end, get<Ir>(rn));
-        if(rv.has_error())
+        if( !rv )
         {
             ec = rv.error();
             return;
@@ -104,7 +104,7 @@ struct parse_sequence
         auto& rv = get<Iv>(vn);
         rv = grammar::parse(
             it, end, get<Ir>(rn));
-        if(rv.has_error())
+        if( !rv )
         {
             ec = rv.error();
             return;
@@ -208,7 +208,7 @@ struct parse_sequence<false, R0, Rn...>
         result<void> rv =
             grammar::parse(
                 it, end, get<Ir>(rn));
-        if(rv.has_error())
+        if( !rv )
         {
             v = rv.error();
             return;
@@ -231,7 +231,7 @@ struct parse_sequence<false, R0, Rn...>
     {
         v = grammar::parse(
             it, end, get<Ir>(rn));
-        if(v.has_error())
+        if( !v )
             return;
         apply(it, end,
             mp11::mp_size_t<Ir+1>{},
diff --git a/include/boost/url/grammar/impl/variant_rule.hpp b/include/boost/url/grammar/impl/variant_rule.hpp
index 71873074..2e367447 100644
--- a/include/boost/url/grammar/impl/variant_rule.hpp
+++ b/include/boost/url/grammar/impl/variant_rule.hpp
@@ -64,7 +64,7 @@ parse_variant(
     auto const it0 = it;
     auto rv = parse(
         it, end, get<I>(rn));
-    if(rv.has_value())
+    if( rv )
         return variant<
             typename R0::value_type,
             typename Rn::value_type...>{
diff --git a/include/boost/url/impl/ipv4_address.ipp b/include/boost/url/impl/ipv4_address.ipp
index 1f39080a..821b691c 100644
--- a/include/boost/url/impl/ipv4_address.ipp
+++ b/include/boost/url/impl/ipv4_address.ipp
@@ -41,7 +41,7 @@ ipv4_address(
     string_view s)
 {
     auto r = parse_ipv4_address(s);
-    if(r.has_error())
+    if( !r)
         detail::throw_invalid_argument();
     *this = r.value();
 }
diff --git a/include/boost/url/impl/ipv6_address.ipp b/include/boost/url/impl/ipv6_address.ipp
index 71b3bde8..6ef3b8bf 100644
--- a/include/boost/url/impl/ipv6_address.ipp
+++ b/include/boost/url/impl/ipv6_address.ipp
@@ -43,7 +43,7 @@ ipv6_address(
     string_view s)
 {
     auto r = parse_ipv6_address(s);
-    if(r.has_error())
+    if( !r )
         detail::throw_invalid_argument();
     *this = r.value();
 }
diff --git a/include/boost/url/impl/pct_encoded_view.ipp b/include/boost/url/impl/pct_encoded_view.ipp
index f7fee1b1..c4c26ae6 100644
--- a/include/boost/url/impl/pct_encoded_view.ipp
+++ b/include/boost/url/impl/pct_encoded_view.ipp
@@ -55,16 +55,16 @@ pct_encoded_view(
 pct_encoded_view::
 pct_encoded_view(
     string_view str,
-    pct_decode_opts opt) noexcept
+    pct_decode_opts opt)
     : p_(str.data())
     , n_(str.size())
     , plus_to_space_(opt.plus_to_space)
 {
-    error_code ec;
     opt.non_normal_is_error = false;
-    dn_ = validate_pct_encoding(str, ec, opt);
-    if (ec.failed())
+    auto rn = validate_pct_encoding(str, opt);
+    if ( !rn )
         detail::throw_invalid_argument();
+    dn_ = *rn;
 }
 
 pct_encoded_view
diff --git a/include/boost/url/impl/pct_encoding.hpp b/include/boost/url/impl/pct_encoding.hpp
index 3ede79db..fc8bfbcf 100644
--- a/include/boost/url/impl/pct_encoding.hpp
+++ b/include/boost/url/impl/pct_encoding.hpp
@@ -22,10 +22,9 @@ namespace boost {
 namespace urls {
 
 template<class CharSet>
-std::size_t
+result<std::size_t>
 validate_pct_encoding(
     string_view s,
-    error_code& ec,
     CharSet const& allowed,
     pct_decode_opts const& opt) noexcept
 {
@@ -48,9 +47,8 @@ validate_pct_encoding(
             *it == '\0')
         {
             // null in input
-            ec = BOOST_URL_ERR(
+            BOOST_URL_RETURN_EC(
                 error::illegal_null);
-            return n;
         }
         if(allowed(*it))
         {
@@ -66,18 +64,16 @@ validate_pct_encoding(
             if(end - it < 2)
             {
                 // missing HEXDIG
-                ec = BOOST_URL_ERR(
+                BOOST_URL_RETURN_EC(
                     error::missing_pct_hexdig);
-                return n;
             }
             auto d0 = grammar::hexdig_value(it[0]);
             auto d1 = grammar::hexdig_value(it[1]);
             if( d0 < 0 || d1 < 0)
             {
                 // expected HEXDIG
-                ec = BOOST_URL_ERR(
+                BOOST_URL_RETURN_EC(
                     error::bad_pct_hexdig);
-                return n;
             }
             it += 2;
             char const c = static_cast<char>(
@@ -89,15 +85,14 @@ validate_pct_encoding(
                 c == '\0')
             {
                 // escaped null
-                ec = BOOST_URL_ERR(
+                BOOST_URL_RETURN_EC(
                     error::illegal_null);
-                return n;
             }
             if( opt.non_normal_is_error &&
                 allowed(c))
             {
                 // escaped unreserved char
-                ec = BOOST_URL_ERR(
+                BOOST_URL_RETURN_EC(
                     error::non_canonical);
                 return n;
             }
@@ -105,24 +100,21 @@ validate_pct_encoding(
             continue;
         }
         // reserved character in input
-        ec = BOOST_URL_ERR(
+        BOOST_URL_RETURN_EC(
             error::illegal_reserved_char);
-        return n;
     }
     BOOST_ASSERT(it == end);
-    ec = {};
     return n;
 }
 
 //------------------------------------------------
 
 template<class CharSet>
-std::size_t
+result<std::size_t>
 pct_decode(
     char* dest,
     char const* end,
     string_view s,
-    error_code& ec,
     CharSet const& allowed,
     pct_decode_opts const& opt) noexcept
 {
@@ -130,18 +122,17 @@ pct_decode(
     BOOST_STATIC_ASSERT(
         grammar::is_charset<CharSet>::value);
 
-    auto const n =
+    auto const rn =
         validate_pct_encoding(
-            s, ec, allowed, opt);
-    if(ec.failed())
-        return 0;
+            s, allowed, opt);
+    if( !rn )
+        return rn;
     auto const n1 =
         pct_decode_unchecked(
             dest, end, s, opt);
-    if(n1 < n)
+    if(n1 < *rn)
     {
-        ec = error::no_space;
-        return n1;
+        return error::no_space;
     }
     return n1;
 }
diff --git a/include/boost/url/impl/pct_encoding.ipp b/include/boost/url/impl/pct_encoding.ipp
index 6d745b84..4e6dec6d 100644
--- a/include/boost/url/impl/pct_encoding.ipp
+++ b/include/boost/url/impl/pct_encoding.ipp
@@ -133,10 +133,9 @@ pct_decode_unchecked(
 
 namespace detail
 {
-std::size_t
+result<std::size_t>
 validate_pct_encoding(
     string_view s,
-    error_code& ec,
     std::true_type) noexcept
 {
     const auto is_safe = [](char c)
@@ -150,33 +149,29 @@ validate_pct_encoding(
     it = grammar::find_if_not(it, end, is_safe);
     while (it != end)
     {
-        if (end - it < 2)
+        if (end - it < 3)
         {
             // missing HEXDIG
-            ec = BOOST_URL_ERR(
+            BOOST_URL_RETURN_EC(
                 error::missing_pct_hexdig);
-            return it - s.data() - pcts * 2;
         }
         if (!grammar::hexdig_chars(it[1]) ||
             !grammar::hexdig_chars(it[2]))
         {
             // expected HEXDIG
-            ec = BOOST_URL_ERR(
+            BOOST_URL_RETURN_EC(
                 error::bad_pct_hexdig);
-            return it - s.data() - pcts * 2;
         }
         it += 3;
         ++pcts;
         it = grammar::find_if_not(it, end, is_safe);
     }
-    ec = {};
     return s.size() - pcts * 2;
 }
 
-std::size_t
+result<std::size_t>
 validate_pct_encoding(
     string_view s,
-    error_code& ec,
     std::false_type) noexcept
 {
     const auto is_safe = [](char c)
@@ -193,75 +188,67 @@ validate_pct_encoding(
         if (*it == '\0')
         {
             // null in input
-            ec = BOOST_URL_ERR(
+            BOOST_URL_RETURN_EC(
                 error::illegal_null);
-            return it - s.data() - pcts * 2;
         }
-        if (end - it < 2)
+        if (end - it < 3)
         {
             // missing HEXDIG
-            ec = BOOST_URL_ERR(
+            BOOST_URL_RETURN_EC(
                 error::missing_pct_hexdig);
-            return it - s.data() - pcts * 2;
         }
         if (!grammar::hexdig_chars(it[1]) ||
             !grammar::hexdig_chars(it[2]))
         {
             // expected HEXDIG
-            ec = BOOST_URL_ERR(
+            BOOST_URL_RETURN_EC(
                 error::bad_pct_hexdig);
-            return it - s.data() - pcts * 2;
         }
         if (it[1] == '0' &&
             it[2] == '0')
         {
             // null in input
-            ec = BOOST_URL_ERR(
+            BOOST_URL_RETURN_EC(
                 error::illegal_null);
-            return it - s.data() - pcts * 2;
         }
         it += 3;
         ++pcts;
         it = grammar::find_if_not(it, end, is_safe);
     }
-    ec = {};
     return s.size() - pcts * 2;
 }
 }
 
-std::size_t
+result<std::size_t>
 validate_pct_encoding(
     string_view s,
-    error_code& ec,
     pct_decode_opts const& opt) noexcept
 {
     if (opt.allow_null)
         return detail::validate_pct_encoding(
-            s, ec, std::true_type{});
+            s, std::true_type{});
     else
        return detail::validate_pct_encoding(
-            s, ec, std::false_type{});
+            s, std::false_type{});
 }
 
-std::size_t
+result<std::size_t>
 pct_decode(
     char* dest,
     char const* end,
     string_view s,
-    error_code& ec,
     pct_decode_opts const& opt) noexcept
 {
-    auto const n =
-        validate_pct_encoding(s, ec, opt);
-    if(ec.failed())
-        return 0;
+    auto const rn =
+        validate_pct_encoding(s, opt);
+    if( !rn )
+        return rn;
     auto const n1 =
         pct_decode_unchecked(
             dest, end, s, opt);
-    if(n1 < n)
+    if(n1 < *rn)
     {
-        ec = error::no_space;
-        return n1;
+        return error::no_space;
     }
     return n1;
 }
diff --git a/include/boost/url/impl/url_base.ipp b/include/boost/url/impl/url_base.ipp
index 85f03b72..677d4b0c 100644
--- a/include/boost/url/impl/url_base.ipp
+++ b/include/boost/url/impl/url_base.ipp
@@ -304,17 +304,15 @@ set_encoded_user(
             this->string());
     s = buf.maybe_copy(s);
     check_invariants();
-    error_code ec;
-    auto const n =
+    auto const rn =
         validate_pct_encoding(
             s,
-            ec,
             detail::user_chars,
             {});
-    if(ec.failed())
+    if( !rn )
         detail::throw_invalid_argument();
     auto dest = set_user_impl(s.size());
-    u_.decoded_[id_user] = n;
+    u_.decoded_[id_user] = *rn;
     if(! s.empty())
     {
         BOOST_ASSERT(dest != nullptr);
@@ -432,14 +430,13 @@ set_encoded_password(
             this->string());
     s = buf.maybe_copy(s);
     check_invariants();
-    error_code ec;
-    auto const n = validate_pct_encoding(
-        s, ec, detail::password_chars, {});
-    if(ec.failed())
+    auto const rn = validate_pct_encoding(
+        s, detail::password_chars, {});
+    if( !rn )
         detail::throw_invalid_argument();
     auto dest =
         set_password_impl(s.size());
-    u_.decoded_[id_pass] = n;
+    u_.decoded_[id_pass] = *rn;
     if(! s.empty())
     {
         BOOST_ASSERT(dest != nullptr);
@@ -685,7 +682,7 @@ set_host(
     // try ipv4
     {
         auto r = parse_ipv4_address(s);
-        if(! r.has_error())
+        if( r )
             return set_host(r.value());
     }
     check_invariants();
@@ -716,7 +713,7 @@ set_host(
     // try ipv4
     {
         auto r = parse_ipv4_address(s.encoded());
-        if(! r.has_error())
+        if( r )
             return set_host(r.value());
     }
     check_invariants();
@@ -1789,12 +1786,11 @@ set_fragment(
 //
 //------------------------------------------------
 
-bool
+result<void>
 url_base::
 resolve_impl(
     url_view_base const& base,
-    url_view_base const& ref,
-    error_code& ec)
+    url_view_base const& ref)
 {
     auto const remove_dot_segments =
         [this]
@@ -1858,12 +1854,9 @@ resolve_impl(
 
     if(! base.has_scheme())
     {
-        ec = error::not_a_base;
-        return false;
+        return error::not_a_base;
     }
 
-    ec = {};
-
     //
     // 5.2.2. Transform References
     // https://datatracker.ietf.org/doc/html/rfc3986#section-5.2.2
@@ -1874,7 +1867,7 @@ resolve_impl(
         reserve(ref.size());
         copy(ref);
         remove_dot_segments();
-        return true;
+        return {};
     }
     if(ref.has_authority())
     {
@@ -1894,7 +1887,7 @@ resolve_impl(
         if(ref.has_fragment())
             set_encoded_fragment(
                 ref.encoded_fragment());
-        return true;
+        return {};
     }
     if(ref.encoded_path().empty())
     {
@@ -1934,7 +1927,7 @@ resolve_impl(
         if(ref.has_fragment())
             set_encoded_fragment(
                 ref.encoded_fragment());
-        return true;
+        return {};
     }
     if(ref.encoded_path().starts_with('/'))
     {
@@ -1955,7 +1948,7 @@ resolve_impl(
         if(ref.has_fragment())
             set_encoded_fragment(
                 ref.encoded_fragment());
-        return true;
+        return {};
     }
     reserve(
         base.u_.offset(id_query) +
@@ -1986,7 +1979,7 @@ resolve_impl(
     if(ref.has_fragment())
         set_encoded_fragment(
             ref.encoded_fragment());
-    return true;
+    return {};
 }
 
 //------------------------------------------------
diff --git a/include/boost/url/pct_encoded_view.hpp b/include/boost/url/pct_encoded_view.hpp
index 23ce2d76..a6a29ae3 100644
--- a/include/boost/url/pct_encoded_view.hpp
+++ b/include/boost/url/pct_encoded_view.hpp
@@ -168,7 +168,7 @@ public:
     explicit
     pct_encoded_view(
         string_view s,
-        pct_decode_opts opt = {}) noexcept;
+        pct_decode_opts opt = {});
 
     //--------------------------------------------
     //
diff --git a/include/boost/url/pct_encoding.hpp b/include/boost/url/pct_encoding.hpp
index 917e54d8..d18dcf25 100644
--- a/include/boost/url/pct_encoding.hpp
+++ b/include/boost/url/pct_encoding.hpp
@@ -86,8 +86,6 @@ struct pct_decode_opts
 
     @param s The percent-encoded string to analyze.
 
-    @param ec Set to the error, if any occurred.
-
     @param opt The options for decoding. If this
     parameter is omitted, the default options
     will be used.
@@ -112,10 +110,9 @@ struct pct_decode_opts
 */
 template<
     class CharSet>
-std::size_t
+result<std::size_t>
 validate_pct_encoding(
     string_view s,
-    error_code& ec,
     CharSet const& allowed,
     pct_decode_opts const& opt = {}) noexcept;
 
@@ -157,8 +154,6 @@ validate_pct_encoding(
 
     @param s The percent-encoded string to analyze.
 
-    @param ec Set to the error, if any occurred.
-
     @param opt The options for decoding. If this
     parameter is omitted, the default options
     will be used.
@@ -174,10 +169,9 @@ validate_pct_encoding(
         @ref pct_decode_unchecked,
 */
 BOOST_URL_DECL
-std::size_t
+result<std::size_t>
 validate_pct_encoding(
     string_view s,
-    error_code& ec,
     pct_decode_opts const& opt = {}) noexcept;
 
 /** Write a string with percent-decoding into a buffer.
@@ -208,7 +202,10 @@ validate_pct_encoding(
 
     @return The number of bytes written to
     the destination buffer, which does not
-    include any null termination.
+    include any null termination. If the
+    destination buffer is too small to hold
+    the result, the result is set to
+    @ref error::no_space.
 
     @param dest A pointer to the
     beginning of the output buffer.
@@ -218,11 +215,6 @@ validate_pct_encoding(
 
     @param s The string to decode.
 
-    @param ec Set to the error, if any
-    occurred. If the destination buffer
-    is too small to hold the result, `ec`
-    is set to @ref error::no_space.
-
     @param opt The options for decoding. If
     this parameter is omitted, the default
     options will be used.
@@ -247,12 +239,11 @@ validate_pct_encoding(
 */
 template<
     class CharSet>
-std::size_t
+result<std::size_t>
 pct_decode(
     char* dest,
     char const* end,
     string_view s,
-    error_code& ec,
     CharSet const& allowed,
     pct_decode_opts const& opt = {}) noexcept;
 
@@ -294,8 +285,6 @@ pct_decode(
 
     @param s The string to decode.
 
-    @param ec Set to the error, if any occurred.
-
     @param opt The options for decoding. If
     this parameter is omitted, the default
     options will be used.
@@ -311,12 +300,11 @@ pct_decode(
         @ref validate_pct_encoding.
 */
 BOOST_URL_DECL
-std::size_t
+result<std::size_t>
 pct_decode(
     char* dest,
     char const* end,
     string_view s,
-    error_code& ec,
     pct_decode_opts const& opt = {}) noexcept;
 
 /** Return the number of bytes needed to hold the string with percent-decoding applied.
diff --git a/include/boost/url/rfc/detail/impl/hier_part_rule.ipp b/include/boost/url/rfc/detail/impl/hier_part_rule.ipp
index 50430b2a..47e3ba3d 100644
--- a/include/boost/url/rfc/detail/impl/hier_part_rule.ipp
+++ b/include/boost/url/rfc/detail/impl/hier_part_rule.ipp
@@ -41,7 +41,7 @@ parse(
         auto rv = grammar::parse(
             it, end,
             path_rootless_rule);
-        if(rv.has_value())
+        if( rv )
         {
             t.path = std::move(*rv);
             BOOST_URL_RETURN(t);
diff --git a/include/boost/url/rfc/detail/impl/host_rule.ipp b/include/boost/url/rfc/detail/impl/host_rule.ipp
index badf77e7..dce519cc 100644
--- a/include/boost/url/rfc/detail/impl/host_rule.ipp
+++ b/include/boost/url/rfc/detail/impl/host_rule.ipp
@@ -74,7 +74,7 @@ parse(
     {
         auto rv = grammar::parse(
             it, end, ipv4_address_rule);
-        if(rv.has_value())
+        if( rv )
         {
             auto const b =
                 rv->to_bytes();
diff --git a/include/boost/url/rfc/detail/impl/path_rules.ipp b/include/boost/url/rfc/detail/impl/path_rules.ipp
index 8f6381c1..afa449d9 100644
--- a/include/boost/url/rfc/detail/impl/path_rules.ipp
+++ b/include/boost/url/rfc/detail/impl/path_rules.ipp
@@ -35,7 +35,7 @@ parse(
     }
     auto rv = grammar::parse(
         it, end, segment_rule);
-    if(rv.has_error())
+    if( !rv )
         return rv.error();
     return *rv;
 }
diff --git a/include/boost/url/rfc/detail/impl/relative_part_rule.ipp b/include/boost/url/rfc/detail/impl/relative_part_rule.ipp
index dc255d1f..a14ce6e4 100644
--- a/include/boost/url/rfc/detail/impl/relative_part_rule.ipp
+++ b/include/boost/url/rfc/detail/impl/relative_part_rule.ipp
@@ -39,7 +39,7 @@ parse(
         auto rv = grammar::parse(
             it, end,
             path_noscheme_rule);
-        if(rv.has_value())
+        if( rv )
         {
             // path-noscheme
             t.path = std::move(*rv);
diff --git a/include/boost/url/url.hpp b/include/boost/url/url.hpp
index 4ec9016a..53145248 100644
--- a/include/boost/url/url.hpp
+++ b/include/boost/url/url.hpp
@@ -293,6 +293,8 @@ private:
     Basic guarantee.
     Calls to allocate may throw.
 
+    @return Error if any occurred
+
     @param base The base URL to resolve against.
 
     @param ref The URL reference to resolve.
@@ -300,8 +302,6 @@ private:
     @param dest The container where the result
     is written, upon success.
 
-    @param ec Set to the error if any occurred.
-
     @par Specification
     <a href="https://datatracker.ietf.org/doc/html/rfc3986#section-5"
         >5. Reference Resolution (rfc3986)</a>
@@ -311,16 +311,15 @@ private:
         @ref url_view.
 */
 inline
-void
+result<void>
 resolve(
     url_view_base const& base,
     url_view_base const& ref,
-    url_base& dest,
-    error_code& ec)
+    url_base& dest)
 {
     BOOST_ASSERT(&dest != &base);
     BOOST_ASSERT(&dest != &ref);
-    dest.resolve_impl(base, ref, ec);
+    return dest.resolve_impl(base, ref);
 }
 
 } // urls
diff --git a/include/boost/url/url_base.hpp b/include/boost/url/url_base.hpp
index 4053e95f..05ad9275 100644
--- a/include/boost/url/url_base.hpp
+++ b/include/boost/url/url_base.hpp
@@ -1448,12 +1448,11 @@ public:
     //--------------------------------------------
 
     friend
-    void
+    result<void>
     resolve(
         url_view_base const& base,
         url_view_base const& ref,
-        url_base& dest,
-        error_code& ec);
+        url_base& dest);
 
 private:
     //--------------------------------------------
@@ -1469,11 +1468,10 @@ private:
     char* shrink_impl(int, int, std::size_t);
 
     BOOST_URL_DECL
-    bool
+    result<void>
     resolve_impl(
         url_view_base const& base,
-        url_view_base const& ref,
-        error_code& ec);
+        url_view_base const& ref);
 };
 
 } // urls
diff --git a/test/unit/params_encoded.cpp b/test/unit/params_encoded.cpp
index 2215260e..097e1a29 100644
--- a/test/unit/params_encoded.cpp
+++ b/test/unit/params_encoded.cpp
@@ -13,6 +13,7 @@
 
 #include <boost/url/url.hpp>
 #include <boost/url/url_view.hpp>
+#include <boost/core/ignore_unused.hpp>
 #include "test_suite.hpp"
 
 namespace boost {
@@ -51,6 +52,26 @@ public:
             BOOST_TEST(u.string() ==
                 "/?k1=1&k2=2&k3=&k4&k5=55555#f");
         }
+        {
+            url u = parse_uri_reference(
+                "/?x#f").value();
+            auto ps = u.encoded_params();
+            BOOST_TEST_THROWS(
+                ps.assign({
+                    { "k1", "1#", true }}),
+                std::invalid_argument);
+            ignore_unused(ps);
+        }
+        {
+            url u = parse_uri_reference(
+                "/?x#f").value();
+            auto ps = u.encoded_params();
+            BOOST_TEST_THROWS(
+                ps.assign({
+                    { "#k1", "", false }}),
+                std::invalid_argument);
+            ignore_unused(ps);
+        }
         {
             url u = parse_uri_reference("/?x#f").value();
             u.encoded_params() = {};
diff --git a/test/unit/pct_encoding.cpp b/test/unit/pct_encoding.cpp
index 45c53639..6acae53d 100644
--- a/test/unit/pct_encoding.cpp
+++ b/test/unit/pct_encoding.cpp
@@ -66,12 +66,11 @@ public:
         {
             // validate_pct_encoding
             {
-                error_code ec;
-                auto n = validate_pct_encoding(
-                    s0, ec, *pcs, opt);
-                if(! BOOST_TEST(! ec.failed()))
+                auto rn = validate_pct_encoding(
+                    s0, *pcs, opt);
+                if(! BOOST_TEST(! rn.has_error()))
                     return;
-                BOOST_TEST_EQ(n, s1.size());
+                BOOST_TEST_EQ(*rn, s1.size());
             }
             // pct_decode to buffer
             {
@@ -79,22 +78,21 @@ public:
                 for(std::size_t i = 0;
                     i < sizeof(buf); ++i)
                 {
-                    error_code ec;
-                    auto const n = pct_decode(
+                    auto const rn = pct_decode(
                         buf, buf + i,
-                            s0, ec, *pcs, opt);
+                            s0, *pcs, opt);
                     if(i < s1.size())
                     {
                         BOOST_TEST(
-                            ec == error::no_space);
-                        BOOST_TEST_LT(n, s1.size());
-                        BOOST_TEST_LE(n, i);
+                            rn.error() == error::no_space);
+                        // BOOST_TEST_LT(n, s1.size());
+                        // BOOST_TEST_LE(n, i);
                         continue;
                     }
-                    BOOST_TEST(! ec.failed());
-                    BOOST_TEST_EQ(n, s1.size());
+                    BOOST_TEST(! rn.has_error());
+                    BOOST_TEST_EQ(*rn, s1.size());
                     BOOST_TEST_EQ(
-                        string_view(buf, n), s1);
+                        string_view(buf, *rn), s1);
                     break;
                 }
             }
@@ -102,10 +100,10 @@ public:
             {
                 std::string s;
                 s.resize(pct_decode_bytes_unchecked(s0));
-                error_code ec;
-                std::size_t n =
-                    pct_decode(&s[0], &s[0] + s.size(), s0, ec, opt);
-                s.resize(n);
+                auto rn =
+                    pct_decode(&s[0], &s[0] + s.size(), s0, opt);
+                BOOST_TEST(rn.has_value());
+                s.resize(*rn);
                 BOOST_TEST_EQ(s, s1);
             }
             // pct_decode() -> std::basic_string
@@ -114,8 +112,8 @@ public:
                 std::basic_string<char,
                     std::char_traits<char>, A> s(A{});
                 s.resize(pct_decode_bytes_unchecked(s0));
-                error_code ec;
-                pct_decode(&s[0], &s[0] + s.size(), s0, ec, opt);
+                auto rn = pct_decode(&s[0], &s[0] + s.size(), s0, opt);
+                BOOST_TEST(rn.has_value());
                 BOOST_TEST_EQ(s, s1);
             }
             // pct_decode_bytes_unchecked
@@ -142,21 +140,19 @@ public:
         {
             // validate_pct_encoding
             {
-                error_code ec;
-                validate_pct_encoding(
-                    s, ec, test_chars{}, opt);
-                BOOST_TEST(ec.failed());
-                if (!ec.failed())
+                auto rn = validate_pct_encoding(
+                    s, test_chars{}, opt);
+                BOOST_TEST(rn.has_error());
+                if (!rn.has_error())
                     BOOST_TEST_EQ(s, "");
             }
             // pct_decode to buffer
             {
                 char buf[16];
-                error_code ec;
-                pct_decode(buf,
+                auto rn = pct_decode(buf,
                     buf + sizeof(buf),
-                        s, ec, *pcs, opt);
-                BOOST_TEST(ec.failed());
+                        s, *pcs, opt);
+                BOOST_TEST(rn.has_error());
             }
             // pct_decode_bytes_unchecked
             {
@@ -432,12 +428,53 @@ public:
         }
     }
 
+    void
+    testValidate()
+    {
+        auto check = [](
+            string_view s,
+            error_code ec,
+            pct_decode_opts opt)
+        {
+            auto r = validate_pct_encoding(s, opt);
+            BOOST_TEST(r.has_error());
+            BOOST_TEST(r.error() == ec);
+        };
+
+        pct_decode_opts opt;
+        opt.allow_null = true;
+        check("%a", error::missing_pct_hexdig, opt);
+        check("%ar", error::bad_pct_hexdig, opt);
+
+        opt.allow_null = false;
+        check(string_view("\0", 1), error::illegal_null, opt);
+        check("%00", error::illegal_null, opt);
+        check("%a", error::missing_pct_hexdig, opt);
+        check("%ar", error::bad_pct_hexdig, opt);
+
+        {
+            std::string dest;
+            dest.resize(1);
+            result<std::size_t> r = pct_decode(
+                &dest[0], &dest[1], "%a", opt);
+            BOOST_TEST_EQ(r.error(), error::missing_pct_hexdig);
+        }
+        {
+            std::string dest;
+            dest.resize(1);
+            result<std::size_t> r = pct_decode(
+                &dest[0], &dest[1], "%aa%aa", opt);
+            BOOST_TEST_EQ(r.error(), error::no_space);
+        }
+    }
+
     void
     run()
     {
         testDecoding();
         testEncode();
         testEncodeExtras();
+        testValidate();
     }
 };
 
diff --git a/test/unit/snippets.cpp b/test/unit/snippets.cpp
index a8f56bcf..4b17da8c 100644
--- a/test/unit/snippets.cpp
+++ b/test/unit/snippets.cpp
@@ -322,8 +322,7 @@ parsing_urls()
         result< url_view > r1 = parse_uri( "https://www.example.com" );
         assert( r1.has_value() );
         url dest;
-        error_code ec;
-        resolve(r1.value(), r0.value(), dest, ec);
+        resolve(r1.value(), r0.value(), dest);
         assert(dest.string() == "https://www.example.com/path/to/file.txt");
         //]
         boost::ignore_unused(dest);
diff --git a/test/unit/url.cpp b/test/unit/url.cpp
index 484ceadb..612813a2 100644
--- a/test/unit/url.cpp
+++ b/test/unit/url.cpp
@@ -1999,9 +1999,8 @@ public:
                 parse_uri_reference(r).value();
             url u = parse_uri(
                 "z://y:x@p.q:69/x/f?q#f" ).value();
-            error_code ec;
-            resolve(ub, ur, u, ec);
-            if(! BOOST_TEST(! ec.failed()))
+            result<void> rv = resolve(ub, ur, u);
+            if(! BOOST_TEST( rv.has_value() ))
                 return;
             BOOST_TEST_EQ(u.string(), m);
         };