diff --git a/src/base58.cpp b/src/base58.cpp
index f9165ed55f..cab99f0cb5 100644
--- a/src/base58.cpp
+++ b/src/base58.cpp
@@ -139,7 +139,7 @@ std::string EncodeBase58Check(Span<const unsigned char> input)
     // add 4-byte hash check to the end
     std::vector<unsigned char> vch(input.begin(), input.end());
     uint256 hash = Hash(vch);
-    vch.insert(vch.end(), (unsigned char*)&hash, (unsigned char*)&hash + 4);
+    vch.insert(vch.end(), hash.data(), hash.data() + 4);
     return EncodeBase58(vch);
 }
 
diff --git a/src/script/miniscript.h b/src/script/miniscript.h
index e739d8031f..75f978457c 100644
--- a/src/script/miniscript.h
+++ b/src/script/miniscript.h
@@ -1798,7 +1798,7 @@ inline NodeRef<Key> Parse(Span<const char> in, const Ctx& ctx)
         // Get threshold
         int next_comma = FindNextChar(in, ',');
         if (next_comma < 1) return false;
-        const auto k_to_integral{ToIntegral<int64_t>(std::string_view(in.begin(), next_comma))};
+        const auto k_to_integral{ToIntegral<int64_t>(std::string_view(in.data(), next_comma))};
         if (!k_to_integral.has_value()) return false;
         const int64_t k{k_to_integral.value()};
         in = in.subspan(next_comma + 1);
@@ -1954,7 +1954,7 @@ inline NodeRef<Key> Parse(Span<const char> in, const Ctx& ctx)
             } else if (Const("after(", in)) {
                 int arg_size = FindNextChar(in, ')');
                 if (arg_size < 1) return {};
-                const auto num{ToIntegral<int64_t>(std::string_view(in.begin(), arg_size))};
+                const auto num{ToIntegral<int64_t>(std::string_view(in.data(), arg_size))};
                 if (!num.has_value() || *num < 1 || *num >= 0x80000000L) return {};
                 constructed.push_back(MakeNodeRef<Key>(internal::NoDupCheck{}, ctx.MsContext(), Fragment::AFTER, *num));
                 in = in.subspan(arg_size + 1);
@@ -1962,7 +1962,7 @@ inline NodeRef<Key> Parse(Span<const char> in, const Ctx& ctx)
             } else if (Const("older(", in)) {
                 int arg_size = FindNextChar(in, ')');
                 if (arg_size < 1) return {};
-                const auto num{ToIntegral<int64_t>(std::string_view(in.begin(), arg_size))};
+                const auto num{ToIntegral<int64_t>(std::string_view(in.data(), arg_size))};
                 if (!num.has_value() || *num < 1 || *num >= 0x80000000L) return {};
                 constructed.push_back(MakeNodeRef<Key>(internal::NoDupCheck{}, ctx.MsContext(), Fragment::OLDER, *num));
                 in = in.subspan(arg_size + 1);
@@ -1974,7 +1974,7 @@ inline NodeRef<Key> Parse(Span<const char> in, const Ctx& ctx)
             } else if (Const("thresh(", in)) {
                 int next_comma = FindNextChar(in, ',');
                 if (next_comma < 1) return {};
-                const auto k{ToIntegral<int64_t>(std::string_view(in.begin(), next_comma))};
+                const auto k{ToIntegral<int64_t>(std::string_view(in.data(), next_comma))};
                 if (!k.has_value() || *k < 1) return {};
                 in = in.subspan(next_comma + 1);
                 // n = 1 here because we read the first WRAPPED_EXPR before reaching THRESH
diff --git a/src/script/solver.h b/src/script/solver.h
index 5a7b685a6f..5b945477c9 100644
--- a/src/script/solver.h
+++ b/src/script/solver.h
@@ -10,6 +10,7 @@
 
 #include <attributes.h>
 #include <script/script.h>
+#include <span.h>
 
 #include <string>
 #include <optional>
@@ -17,7 +18,6 @@
 #include <vector>
 
 class CPubKey;
-template <typename C> class Span;
 
 enum class TxoutType {
     NONSTANDARD,
diff --git a/src/serialize.h b/src/serialize.h
index 2af998f3c5..6384c95dba 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -264,6 +264,7 @@ template<typename Stream> inline void Serialize(Stream& s, int64_t a ) { ser_wri
 template<typename Stream> inline void Serialize(Stream& s, uint64_t a) { ser_writedata64(s, a); }
 template <typename Stream, BasicByte B, int N> void Serialize(Stream& s, const B (&a)[N]) { s.write(MakeByteSpan(a)); }
 template <typename Stream, BasicByte B, std::size_t N> void Serialize(Stream& s, const std::array<B, N>& a) { s.write(MakeByteSpan(a)); }
+template <typename Stream, BasicByte B, std::size_t N> void Serialize(Stream& s, std::span<B, N> span) { s.write(std::as_bytes(span)); }
 template <typename Stream, BasicByte B> void Serialize(Stream& s, Span<B> span) { s.write(AsBytes(span)); }
 
 template <typename Stream, CharNotInt8 V> void Unserialize(Stream&, V) = delete; // char serialization forbidden. Use uint8_t or int8_t
@@ -278,6 +279,7 @@ template<typename Stream> inline void Unserialize(Stream& s, int64_t& a ) { a =
 template<typename Stream> inline void Unserialize(Stream& s, uint64_t& a) { a = ser_readdata64(s); }
 template <typename Stream, BasicByte B, int N> void Unserialize(Stream& s, B (&a)[N]) { s.read(MakeWritableByteSpan(a)); }
 template <typename Stream, BasicByte B, std::size_t N> void Unserialize(Stream& s, std::array<B, N>& a) { s.read(MakeWritableByteSpan(a)); }
+template <typename Stream, BasicByte B, std::size_t N> void Unserialize(Stream& s, std::span<B, N> span) { s.read(std::as_writable_bytes(span)); }
 template <typename Stream, BasicByte B> void Unserialize(Stream& s, Span<B> span) { s.read(AsWritableBytes(span)); }
 
 template <typename Stream> inline void Serialize(Stream& s, bool a) { uint8_t f = a; ser_writedata8(s, f); }
diff --git a/src/span.h b/src/span.h
index 3c5028f0b7..93718f6189 100644
--- a/src/span.h
+++ b/src/span.h
@@ -248,9 +248,8 @@ template <typename T>
 T& SpanPopBack(Span<T>& span)
 {
     size_t size = span.size();
-    ASSERT_IF_DEBUG(size > 0);
-    T& back = span[size - 1];
-    span = Span<T>(span.data(), size - 1);
+    T& back = span.back();
+    span = span.first(size - 1);
     return back;
 }
 
diff --git a/src/streams.h b/src/streams.h
index 64dbfbff14..e5316da7e7 100644
--- a/src/streams.h
+++ b/src/streams.h
@@ -79,7 +79,7 @@ public:
             memcpy(vchData.data() + nPos, src.data(), nOverwrite);
         }
         if (nOverwrite < src.size()) {
-            vchData.insert(vchData.end(), UCharCast(src.data()) + nOverwrite, UCharCast(src.end()));
+            vchData.insert(vchData.end(), UCharCast(src.data()) + nOverwrite, UCharCast(src.data() + src.size()));
         }
         nPos += src.size();
     }
diff --git a/src/test/script_tests.cpp b/src/test/script_tests.cpp
index 59eb90bd27..8753ddee37 100644
--- a/src/test/script_tests.cpp
+++ b/src/test/script_tests.cpp
@@ -1700,9 +1700,8 @@ BOOST_AUTO_TEST_CASE(bip341_keypath_test_vectors)
             BOOST_CHECK_EQUAL(HexStr(sighash), input["intermediary"]["sigHash"].get_str());
 
             // To verify the sigmsg, hash the expected sigmsg, and compare it with the (expected) sighash.
-            BOOST_CHECK_EQUAL(HexStr((HashWriter{HASHER_TAPSIGHASH} << Span{ParseHex(input["intermediary"]["sigMsg"].get_str())}).GetSHA256()), input["intermediary"]["sigHash"].get_str());
+            BOOST_CHECK_EQUAL(HexStr((HashWriter{HASHER_TAPSIGHASH} << std::span<const uint8_t>{ParseHex(input["intermediary"]["sigMsg"].get_str())}).GetSHA256()), input["intermediary"]["sigHash"].get_str());
         }
-
     }
 }
 
diff --git a/src/test/serialize_tests.cpp b/src/test/serialize_tests.cpp
index b28e1b4196..7e403694e2 100644
--- a/src/test/serialize_tests.cpp
+++ b/src/test/serialize_tests.cpp
@@ -304,7 +304,7 @@ public:
         if (s.template GetParams<BaseFormat>().m_base_format == BaseFormat::RAW) {
             s << m_base_data;
         } else {
-            s << Span{HexStr(Span{&m_base_data, 1})};
+            s << std::span<const char>{HexStr(Span{&m_base_data, 1})};
         }
     }
 
diff --git a/src/test/util/net.h b/src/test/util/net.h
index 043e317bf0..d3aefda4f0 100644
--- a/src/test/util/net.h
+++ b/src/test/util/net.h
@@ -12,6 +12,7 @@
 #include <netaddress.h>
 #include <node/connection_types.h>
 #include <node/eviction.h>
+#include <span.h>
 #include <sync.h>
 #include <util/sock.h>
 
@@ -28,9 +29,6 @@
 
 class FastRandomContext;
 
-template <typename C>
-class Span;
-
 struct ConnmanTestMsg : public CConnman {
     using CConnman::CConnman;
 
diff --git a/src/util/hasher.h b/src/util/hasher.h
index 3ad6d5bb94..e4594c7dda 100644
--- a/src/util/hasher.h
+++ b/src/util/hasher.h
@@ -8,13 +8,12 @@
 #include <crypto/common.h>
 #include <crypto/siphash.h>
 #include <primitives/transaction.h>
+#include <span.h>
 #include <uint256.h>
 
 #include <cstdint>
 #include <cstring>
 
-template <typename C> class Span;
-
 class SaltedTxidHasher
 {
 private:
diff --git a/src/wallet/test/db_tests.cpp b/src/wallet/test/db_tests.cpp
index ea32199497..41951e84c8 100644
--- a/src/wallet/test/db_tests.cpp
+++ b/src/wallet/test/db_tests.cpp
@@ -34,9 +34,9 @@ inline std::ostream& operator<<(std::ostream& os, const std::pair<const Serializ
 
 namespace wallet {
 
-static Span<const std::byte> StringBytes(std::string_view str)
+inline std::span<const std::byte> StringBytes(std::string_view str)
 {
-    return AsBytes<const char>({str.data(), str.size()});
+    return std::as_bytes(std::span{str});
 }
 
 static SerializeData StringData(std::string_view str)