diff --git a/src/cuckoocache.h b/src/cuckoocache.h
--- a/src/cuckoocache.h
+++ b/src/cuckoocache.h
@@ -415,7 +415,7 @@
         std::array<uint32_t, 8> locs = compute_hashes(e);
         // Make sure we have not already inserted this element.
         // If we have, make sure that it does not get deleted.
-        for (uint32_t loc : locs)
+        for (const uint32_t loc : locs)
             if (table[loc] == e) {
                 please_keep(loc);
                 epoch_flags[loc] = last_epoch;
@@ -423,7 +423,7 @@
             }
         for (uint8_t depth = 0; depth < depth_limit; ++depth) {
             // First try to insert to an empty slot, if one exists
-            for (uint32_t loc : locs) {
+            for (const uint32_t loc : locs) {
                 if (!collection_flags.bit_is_set(loc)) continue;
                 table[loc] = std::move(e);
                 please_keep(loc);
@@ -488,7 +488,7 @@
      */
     inline bool contains(const Element &e, const bool erase) const {
         std::array<uint32_t, 8> locs = compute_hashes(e);
-        for (uint32_t loc : locs) {
+        for (const uint32_t loc : locs) {
             if (table[loc] == e) {
                 if (erase) {
                     allow_erase(loc);
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -1050,7 +1050,7 @@
     // Erase orphan transactions included or precluded by this block
     if (vOrphanErase.size()) {
         int nErased = 0;
-        for (uint256 &orphanId : vOrphanErase) {
+        for (const uint256 &orphanId : vOrphanErase) {
             nErased += EraseOrphanTx(orphanId);
         }
         LogPrint(BCLog::MEMPOOL,
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -439,7 +439,7 @@
 
 #ifdef ENABLE_WALLET
     window->removeAllWallets();
-    for (WalletModel *walletModel : m_wallet_models) {
+    for (const WalletModel *walletModel : m_wallet_models) {
         delete walletModel;
     }
     m_wallet_models.clear();
diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
--- a/src/qt/bitcoingui.cpp
+++ b/src/qt/bitcoingui.cpp
@@ -1295,7 +1295,7 @@
  * mouse events. */
 void UnitDisplayStatusBarControl::createContextMenu() {
     menu = new QMenu(this);
-    for (BitcoinUnits::Unit u : BitcoinUnits::availableUnits()) {
+    for (const BitcoinUnits::Unit u : BitcoinUnits::availableUnits()) {
         QAction *menuAction = new QAction(QString(BitcoinUnits::name(u)), this);
         menuAction->setData(QVariant(u));
         menu->addAction(menuAction);
diff --git a/src/qt/peertablemodel.cpp b/src/qt/peertablemodel.cpp
--- a/src/qt/peertablemodel.cpp
+++ b/src/qt/peertablemodel.cpp
@@ -61,7 +61,7 @@
             interfaces::Node::NodesStats nodes_stats;
             node.getNodesStats(nodes_stats);
             cachedNodeStats.reserve(nodes_stats.size());
-            for (auto &node_stats : nodes_stats) {
+            for (const auto &node_stats : nodes_stats) {
                 CNodeCombinedStats stats;
                 stats.nodeStats = std::get<0>(node_stats);
                 stats.fNodeStateStatsAvailable = std::get<1>(node_stats);
diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
--- a/src/qt/sendcoinsdialog.cpp
+++ b/src/qt/sendcoinsdialog.cpp
@@ -357,7 +357,7 @@
     questionString.append("<hr />");
     Amount totalAmount = currentTransaction.getTotalTransactionAmount() + txFee;
     QStringList alternativeUnits;
-    for (BitcoinUnits::Unit u : BitcoinUnits::availableUnits()) {
+    for (const BitcoinUnits::Unit u : BitcoinUnits::availableUnits()) {
         if (u != model->getOptionsModel()->getDisplayUnit()) {
             alternativeUnits.append(
                 BitcoinUnits::formatHtmlWithUnit(u, totalAmount));
diff --git a/src/qt/splashscreen.cpp b/src/qt/splashscreen.cpp
--- a/src/qt/splashscreen.cpp
+++ b/src/qt/splashscreen.cpp
@@ -217,7 +217,7 @@
     // Disconnect signals from client
     m_handler_init_message->disconnect();
     m_handler_show_progress->disconnect();
-    for (auto &handler : m_connected_wallet_handlers) {
+    for (const auto &handler : m_connected_wallet_handlers) {
         handler->disconnect();
     }
     m_connected_wallet_handlers.clear();
diff --git a/src/qt/trafficgraphwidget.cpp b/src/qt/trafficgraphwidget.cpp
--- a/src/qt/trafficgraphwidget.cpp
+++ b/src/qt/trafficgraphwidget.cpp
@@ -133,10 +133,10 @@
     }
 
     float tmax = 0.0f;
-    for (float f : vSamplesIn) {
+    for (const float f : vSamplesIn) {
         if (f > tmax) tmax = f;
     }
-    for (float f : vSamplesOut) {
+    for (const float f : vSamplesOut) {
         if (f > tmax) tmax = f;
     }
     fMax = tmax;
diff --git a/src/qt/transactiondesc.cpp b/src/qt/transactiondesc.cpp
--- a/src/qt/transactiondesc.cpp
+++ b/src/qt/transactiondesc.cpp
@@ -169,14 +169,14 @@
                    BitcoinUnits::formatHtmlWithUnit(unit, nNet) + "<br>";
     } else {
         isminetype fAllFromMe = ISMINE_SPENDABLE;
-        for (isminetype mine : wtx.txin_is_mine) {
+        for (const isminetype mine : wtx.txin_is_mine) {
             if (fAllFromMe > mine) {
                 fAllFromMe = mine;
             }
         }
 
         isminetype fAllToMe = ISMINE_SPENDABLE;
-        for (isminetype mine : wtx.txout_is_mine) {
+        for (const isminetype mine : wtx.txout_is_mine) {
             if (fAllToMe > mine) {
                 fAllToMe = mine;
             }
diff --git a/src/qt/transactionrecord.cpp b/src/qt/transactionrecord.cpp
--- a/src/qt/transactionrecord.cpp
+++ b/src/qt/transactionrecord.cpp
@@ -75,7 +75,7 @@
     } else {
         bool involvesWatchAddress = false;
         isminetype fAllFromMe = ISMINE_SPENDABLE;
-        for (isminetype mine : wtx.txin_is_mine) {
+        for (const isminetype mine : wtx.txin_is_mine) {
             if (mine & ISMINE_WATCH_ONLY) {
                 involvesWatchAddress = true;
             }
@@ -85,7 +85,7 @@
         }
 
         isminetype fAllToMe = ISMINE_SPENDABLE;
-        for (isminetype mine : wtx.txout_is_mine) {
+        for (const isminetype mine : wtx.txout_is_mine) {
             if (mine & ISMINE_WATCH_ONLY) {
                 involvesWatchAddress = true;
             }
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -500,7 +500,7 @@
     const CTxMemPool::txiter &it = g_mempool.mapTx.find(tx.GetId());
     const CTxMemPool::setEntries &setChildren =
         g_mempool.GetMemPoolChildren(it);
-    for (const CTxMemPool::txiter &childiter : setChildren) {
+    for (CTxMemPool::txiter childiter : setChildren) {
         spent.push_back(childiter->GetTx().GetId().ToString());
     }
 
diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -207,7 +207,7 @@
             obj.pushKV("synced_headers", statestats.nSyncHeight);
             obj.pushKV("synced_blocks", statestats.nCommonHeight);
             UniValue heights(UniValue::VARR);
-            for (int height : statestats.vHeightInFlight) {
+            for (const int height : statestats.vHeightInFlight) {
                 heights.push_back(height);
             }
             obj.pushKV("inflight", heights);
diff --git a/src/test/coins_tests.cpp b/src/test/coins_tests.cpp
--- a/src/test/coins_tests.cpp
+++ b/src/test/coins_tests.cpp
@@ -777,7 +777,7 @@
 // while still verifying that the CoinsViewCache::AddCoin implementation ignores
 // base values.
 template <typename... Args> static void CheckAddCoin(Args &&... args) {
-    for (Amount base_value : {ABSENT, PRUNED, VALUE1}) {
+    for (const Amount base_value : {ABSENT, PRUNED, VALUE1}) {
         CheckAddCoinBase(base_value, std::forward<Args>(args)...);
     }
 }
@@ -897,11 +897,11 @@
     // they would be too repetitive (the parent cache is never updated in these
     // cases). The loop below covers these cases and makes sure the parent cache
     // is always left unchanged.
-    for (Amount parent_value : {ABSENT, PRUNED, VALUE1}) {
-        for (Amount child_value : {ABSENT, PRUNED, VALUE2}) {
-            for (char parent_flags :
+    for (const Amount parent_value : {ABSENT, PRUNED, VALUE1}) {
+        for (const Amount child_value : {ABSENT, PRUNED, VALUE2}) {
+            for (const char parent_flags :
                  parent_value == ABSENT ? ABSENT_FLAGS : FLAGS) {
-                for (char child_flags :
+                for (const char child_flags :
                      child_value == ABSENT ? ABSENT_FLAGS : CLEAN_FLAGS) {
                     CheckWriteCoin(parent_value, child_value, parent_value,
                                    parent_flags, child_flags, parent_flags);
diff --git a/src/test/cuckoocache_tests.cpp b/src/test/cuckoocache_tests.cpp
--- a/src/test/cuckoocache_tests.cpp
+++ b/src/test/cuckoocache_tests.cpp
@@ -70,12 +70,12 @@
      */
     std::vector<uint256> hashes_insert_copy = hashes;
     /** Do the insert */
-    for (uint256 &h : hashes_insert_copy) {
+    for (const uint256 &h : hashes_insert_copy) {
         set.insert(h);
     }
     /** Count the hits */
     uint32_t count = 0;
-    for (uint256 &h : hashes) {
+    for (const uint256 &h : hashes) {
         count += set.contains(h, false);
     }
     double hit_rate = double(count) / double(n_insert);
@@ -327,7 +327,7 @@
             for (uint32_t i = n_insert - (n_insert / 4); i < n_insert; ++i) {
                 reads.push_back(inserts[i]);
             }
-            for (auto h : inserts) {
+            for (const auto &h : inserts) {
                 c.insert(h);
             }
         }
diff --git a/src/test/dbwrapper_tests.cpp b/src/test/dbwrapper_tests.cpp
--- a/src/test/dbwrapper_tests.cpp
+++ b/src/test/dbwrapper_tests.cpp
@@ -25,7 +25,7 @@
 
 BOOST_AUTO_TEST_CASE(dbwrapper) {
     // Perform tests both obfuscated and non-obfuscated.
-    for (bool obfuscate : {false, true}) {
+    for (const bool obfuscate : {false, true}) {
         fs::path ph = SetDataDir(
             std::string("dbwrapper").append(obfuscate ? "_true" : "_false"));
         CDBWrapper dbw(ph, (1 << 20), true, false, obfuscate);
@@ -46,7 +46,7 @@
 // Test batch operations
 BOOST_AUTO_TEST_CASE(dbwrapper_batch) {
     // Perform tests both obfuscated and non-obfuscated.
-    for (bool obfuscate : {false, true}) {
+    for (const bool obfuscate : {false, true}) {
         fs::path ph = SetDataDir(std::string("dbwrapper_batch")
                                      .append(obfuscate ? "_true" : "_false"));
         CDBWrapper dbw(ph, (1 << 20), true, false, obfuscate);
@@ -82,7 +82,7 @@
 
 BOOST_AUTO_TEST_CASE(dbwrapper_iterator) {
     // Perform tests both obfuscated and non-obfuscated.
-    for (bool obfuscate : {false, true}) {
+    for (const bool obfuscate : {false, true}) {
         fs::path ph = SetDataDir(std::string("dbwrapper_iterator")
                                      .append(obfuscate ? "_true" : "_false"));
         CDBWrapper dbw(ph, (1 << 20), true, false, obfuscate);
@@ -224,7 +224,7 @@
         }
     }
 
-    for (int seek_start : {0x00, 0x80}) {
+    for (const int seek_start : {0x00, 0x80}) {
         it->Seek((uint8_t)seek_start);
         for (unsigned int x = seek_start; x < 255; ++x) {
             uint8_t key;
@@ -302,7 +302,7 @@
 
     std::unique_ptr<CDBIterator> it(
         const_cast<CDBWrapper &>(dbw).NewIterator());
-    for (int seek_start : {0, 5}) {
+    for (const int seek_start : {0, 5}) {
         snprintf(buf, sizeof(buf), "%d", seek_start);
         StringContentsSerializer seek_key(buf);
         it->Seek(seek_key);
diff --git a/src/test/getarg_tests.cpp b/src/test/getarg_tests.cpp
--- a/src/test/getarg_tests.cpp
+++ b/src/test/getarg_tests.cpp
@@ -25,7 +25,7 @@
 
     // Convert to char*:
     std::vector<const char *> vecChar;
-    for (std::string &s : vecArg) {
+    for (const std::string &s : vecArg) {
         vecChar.push_back(s.c_str());
     }
 
diff --git a/src/test/key_io_tests.cpp b/src/test/key_io_tests.cpp
--- a/src/test/key_io_tests.cpp
+++ b/src/test/key_io_tests.cpp
@@ -155,8 +155,9 @@
         std::string exp_base58string = test[0].get_str();
 
         // must be invalid as public and as private key
-        for (auto chain : {CBaseChainParams::MAIN, CBaseChainParams::TESTNET,
-                           CBaseChainParams::REGTEST}) {
+        for (const auto &chain :
+             {CBaseChainParams::MAIN, CBaseChainParams::TESTNET,
+              CBaseChainParams::REGTEST}) {
             SelectParams(chain);
             destination = DecodeLegacyAddr(exp_base58string, Params());
             BOOST_CHECK_MESSAGE(!IsValidDestination(destination),
diff --git a/src/test/skiplist_tests.cpp b/src/test/skiplist_tests.cpp
--- a/src/test/skiplist_tests.cpp
+++ b/src/test/skiplist_tests.cpp
@@ -165,7 +165,8 @@
 
 BOOST_AUTO_TEST_CASE(findearliestatleast_edge_test) {
     std::list<CBlockIndex> blocks;
-    for (unsigned int timeMax : {100, 100, 100, 200, 200, 200, 300, 300, 300}) {
+    for (const unsigned int timeMax :
+         {100, 100, 100, 200, 200, 200, 300, 300, 300}) {
         CBlockIndex *prev = blocks.empty() ? nullptr : &blocks.back();
         blocks.emplace_back();
         blocks.back().nHeight = prev ? prev->nHeight + 1 : 0;
diff --git a/src/test/util_tests.cpp b/src/test/util_tests.cpp
--- a/src/test/util_tests.cpp
+++ b/src/test/util_tests.cpp
@@ -235,7 +235,7 @@
     testArgs.ParseParameters(7, (char **)argv_test, error);
 
     // Each letter should be set.
-    for (char opt : "abcdef") {
+    for (const char opt : "abcdef") {
         BOOST_CHECK(testArgs.IsArgSet({'-', opt}) || !opt);
     }
 
@@ -374,7 +374,7 @@
                 test_args.GetArg("-zzz", "xxx") == "xxx" &&
                 test_args.GetArg("-iii", "xxx") == "xxx");
 
-    for (bool def : {false, true}) {
+    for (const bool def : {false, true}) {
         BOOST_CHECK(test_args.GetBoolArg("-a", def) &&
                     test_args.GetBoolArg("-b", def) &&
                     !test_args.GetBoolArg("-ccc", def) &&
diff --git a/src/timedata.cpp b/src/timedata.cpp
--- a/src/timedata.cpp
+++ b/src/timedata.cpp
@@ -88,7 +88,7 @@
                 // If nobody has a time different than ours but within 5 minutes
                 // of ours, give a warning
                 bool fMatch = false;
-                for (int64_t nOffset : vSorted) {
+                for (const int64_t nOffset : vSorted) {
                     if (nOffset != 0 && abs64(nOffset) < 5 * 60) fMatch = true;
                 }
 
@@ -107,7 +107,7 @@
         }
 
         if (LogAcceptCategory(BCLog::NET)) {
-            for (int64_t n : vSorted) {
+            for (const int64_t n : vSorted) {
                 LogPrintToBeContinued(BCLog::NET, "%+d  ", n);
             }
 
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -242,7 +242,7 @@
         }
 
         const setEntries &setMemPoolParents = GetMemPoolParents(stageit);
-        for (const txiter &phash : setMemPoolParents) {
+        for (txiter phash : setMemPoolParents) {
             // If this is a new ancestor, add it.
             if (setAncestors.count(phash) == 0) {
                 parentHashes.insert(phash);
@@ -509,7 +509,7 @@
         stage.erase(it);
 
         const setEntries &setChildren = GetMemPoolChildren(it);
-        for (const txiter &childiter : setChildren) {
+        for (txiter childiter : setChildren) {
             if (!setDescendants.count(childiter)) {
                 stage.insert(childiter);
             }
@@ -1037,7 +1037,7 @@
                               MemPoolRemovalReason reason) {
     AssertLockHeld(cs);
     UpdateForRemoveFromMempool(stage, updateDescendants);
-    for (const txiter &it : stage) {
+    for (txiter it : stage) {
         removeUnchecked(it, reason);
     }
 }
diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -416,7 +416,7 @@
             // lock on a mempool input, so we can use the return value of
             // CheckSequenceLocks to indicate the LockPoints validity.
             int maxInputHeight = 0;
-            for (int height : prevheights) {
+            for (const int height : prevheights) {
                 // Can ignore mempool inputs since we'll fail if they had
                 // non-zero locks.
                 if (height != tip->nHeight + 1) {
@@ -5017,7 +5017,7 @@
     setDirtyBlockIndex.clear();
     setDirtyFileInfo.clear();
 
-    for (BlockMap::value_type &entry : mapBlockIndex) {
+    for (const BlockMap::value_type &entry : mapBlockIndex) {
         delete entry.second;
     }
 
@@ -5267,7 +5267,7 @@
 
     // Build forward-pointing map of the entire block tree.
     std::multimap<CBlockIndex *, CBlockIndex *> forward;
-    for (auto &entry : mapBlockIndex) {
+    for (const auto &entry : mapBlockIndex) {
         forward.emplace(entry.second->pprev, entry.second);
     }
 
diff --git a/src/wallet/db.cpp b/src/wallet/db.cpp
--- a/src/wallet/db.cpp
+++ b/src/wallet/db.cpp
@@ -548,7 +548,7 @@
             // be implemented, so no equality checks are needed at all. (Newer
             // versions of BDB have an set_lk_exclusive method for this
             // purpose, but the older version we use does not.)
-            for (auto &dbenv : g_dbenvs) {
+            for (const auto &dbenv : g_dbenvs) {
                 CheckUniqueFileid(dbenv.second, strFilename, *pdb_temp);
             }
 
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -43,7 +43,7 @@
 
 static std::string EncodeDumpString(const std::string &str) {
     std::stringstream ret;
-    for (uint8_t c : str) {
+    for (const uint8_t c : str) {
         if (c <= 32 || c >= 128 || c == '%') {
             ret << '%' << HexStr(&c, &c + 1);
         } else {
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -3184,7 +3184,7 @@
 
     UniValue ret(UniValue::VARR);
 
-    for (COutPoint &output : vOutpts) {
+    for (const COutPoint &output : vOutpts) {
         UniValue o(UniValue::VOBJ);
 
         o.pushKV("txid", output.GetTxId().GetHex());
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1916,7 +1916,7 @@
     }
 
     // Try to add wallet transactions to memory pool.
-    for (std::pair<const int64_t, CWalletTx *> &item : mapSorted) {
+    for (const std::pair<const int64_t, CWalletTx *> &item : mapSorted) {
         CWalletTx &wtx = *(item.second);
         CValidationState state;
         wtx.AcceptToMemoryPool(maxTxFee, state);
@@ -2199,7 +2199,7 @@
         mapSorted.insert(std::make_pair(wtx.nTimeReceived, &wtx));
     }
 
-    for (std::pair<const unsigned int, CWalletTx *> &item : mapSorted) {
+    for (const std::pair<const unsigned int, CWalletTx *> &item : mapSorted) {
         CWalletTx &wtx = *item.second;
         if (wtx.RelayWalletTransaction(connman)) {
             result.push_back(wtx.GetId());
@@ -2520,7 +2520,7 @@
 
     AvailableCoins(availableCoins);
 
-    for (auto &coin : availableCoins) {
+    for (const auto &coin : availableCoins) {
         CTxDestination address;
         if (coin.fSpendable &&
             ExtractDestination(
@@ -3543,12 +3543,12 @@
     LOCK(cs_wallet);
     WalletBatch batch(*database);
 
-    for (int64_t nIndex : setInternalKeyPool) {
+    for (const int64_t nIndex : setInternalKeyPool) {
         batch.ErasePool(nIndex);
     }
     setInternalKeyPool.clear();
 
-    for (int64_t nIndex : setExternalKeyPool) {
+    for (const int64_t nIndex : setExternalKeyPool) {
         batch.ErasePool(nIndex);
     }
     setExternalKeyPool.clear();
@@ -3910,7 +3910,7 @@
         // Make a set of all the groups hit by this new group.
         std::set<std::set<CTxDestination> *> hits;
         std::map<CTxDestination, std::set<CTxDestination> *>::iterator it;
-        for (CTxDestination address : _grouping) {
+        for (const CTxDestination &address : _grouping) {
             if ((it = setmap.find(address)) != setmap.end()) {
                 hits.insert((*it).second);
             }
@@ -3927,13 +3927,13 @@
         uniqueGroupings.insert(merged);
 
         // Update setmap.
-        for (CTxDestination element : *merged) {
+        for (const CTxDestination &element : *merged) {
             setmap[element] = merged;
         }
     }
 
     std::set<std::set<CTxDestination>> ret;
-    for (std::set<CTxDestination> *uniqueGrouping : uniqueGroupings) {
+    for (const std::set<CTxDestination> *uniqueGrouping : uniqueGroupings) {
         ret.insert(*uniqueGrouping);
         delete uniqueGrouping;
     }