diff --git a/.clang-tidy b/.clang-tidy
index 0b130f31de08..d5054062dacc 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -51,7 +51,6 @@ Checks: >
         -modernize-use-nodiscard,
         -modernize-use-trailing-return-type,
         -performance-avoid-endl,
-        -performance-enum-size,
         -performance-inefficient-string-concatenation,
         -performance-no-automatic-move,
         -performance-noexcept-swap,
diff --git a/clang-tidy.md b/clang-tidy.md
index 108af31a354e..3cdfcbf9510a 100644
--- a/clang-tidy.md
+++ b/clang-tidy.md
@@ -129,7 +129,6 @@ We run this separately via `clang-include-cleaner` in the `iwyu.yml` workflow as
 `performance-noexcept-swap`<br/>
 `bugprone-switch-missing-default-case`<br/>
 `bugprone-empty-catch`<br/>
-`performance-enum-size`<br/>
 `readability-avoid-nested-conditional-operator`</br>
 
 To be evaluated (need to remove exclusion).
diff --git a/cli/cmdlineparser.h b/cli/cmdlineparser.h
index 4e41094ee101..607608de6cf0 100644
--- a/cli/cmdlineparser.h
+++ b/cli/cmdlineparser.h
@@ -20,6 +20,7 @@
 #define CMDLINE_PARSER_H
 
 #include <cstddef>
+#include <cstdint>
 #include <list>
 #include <string>
 #include <utility>
@@ -56,7 +57,7 @@ class CmdLineParser {
      */
     CmdLineParser(CmdLineLogger &logger, Settings &settings, Suppressions &suppressions);
 
-    enum class Result { Success, Exit, Fail };
+    enum class Result : std::uint8_t { Success, Exit, Fail };
 
     /**
      * @brief Parse command line args and fill settings and file lists
diff --git a/cli/processexecutor.cpp b/cli/processexecutor.cpp
index de847015ded1..0194fc55f4a9 100644
--- a/cli/processexecutor.cpp
+++ b/cli/processexecutor.cpp
@@ -56,7 +56,7 @@
 #include <sys/prctl.h>
 #endif
 
-enum class Color;
+enum class Color : std::uint8_t ;
 
 // NOLINTNEXTLINE(misc-unused-using-decls) - required for FD_ZERO
 using std::memset;
@@ -72,7 +72,7 @@ ProcessExecutor::ProcessExecutor(const std::list<std::pair<std::string, std::siz
 namespace {
     class PipeWriter : public ErrorLogger {
     public:
-        enum PipeSignal {REPORT_OUT='1',REPORT_ERROR='2', CHILD_END='5'};
+        enum PipeSignal : std::uint8_t {REPORT_OUT='1',REPORT_ERROR='2', CHILD_END='5'};
 
         explicit PipeWriter(int pipe) : mWpipe(pipe) {}
 
diff --git a/cli/threadexecutor.cpp b/cli/threadexecutor.cpp
index 9f44d5b1553b..68bb7f17c75b 100644
--- a/cli/threadexecutor.cpp
+++ b/cli/threadexecutor.cpp
@@ -37,7 +37,7 @@
 #include <utility>
 #include <vector>
 
-enum class Color;
+enum class Color : std::uint8_t ;
 
 ThreadExecutor::ThreadExecutor(const std::list<std::pair<std::string, std::size_t>> &files, const std::list<FileSettings>& fileSettings, const Settings &settings, SuppressionList &suppressions, ErrorLogger &errorLogger, CppCheck::ExecuteCmdFn executeCommand)
     : Executor(files, fileSettings, settings, suppressions, errorLogger)
diff --git a/gui/checkthread.h b/gui/checkthread.h
index 2b415bef6c51..21fe3b3da8c1 100644
--- a/gui/checkthread.h
+++ b/gui/checkthread.h
@@ -24,6 +24,7 @@
 #include "suppressions.h"
 
 #include <atomic>
+#include <cstdint>
 #include <string>
 #include <vector>
 
@@ -115,7 +116,7 @@ class CheckThread : public QThread {
      * has been completed. Thread must be stopped cleanly, just terminating thread
      * likely causes unpredictable side-effects.
      */
-    enum State {
+    enum State : std::uint8_t {
         Running, /**< The thread is checking. */
         Stopping, /**< The thread will stop after current work. */
         Stopped, /**< The thread has been stopped. */
diff --git a/gui/codeeditor.h b/gui/codeeditor.h
index 6e06db9881f1..f627d8b4a795 100644
--- a/gui/codeeditor.h
+++ b/gui/codeeditor.h
@@ -19,6 +19,8 @@
 #ifndef CODEEDITOR_H
 #define CODEEDITOR_H
 
+#include <cstdint>
+
 #include <QObject>
 #include <QPlainTextEdit>
 #include <QRegularExpression>
@@ -51,7 +53,7 @@ class Highlighter : public QSyntaxHighlighter {
     void highlightBlock(const QString &text) override;
 
 private:
-    enum RuleRole {
+    enum RuleRole : std::uint8_t {
         Keyword = 1,
         Class   = 2,
         Comment = 3,
diff --git a/gui/cppchecklibrarydata.h b/gui/cppchecklibrarydata.h
index 2ccf9d93ba30..a442780c3c2c 100644
--- a/gui/cppchecklibrarydata.h
+++ b/gui/cppchecklibrarydata.h
@@ -19,6 +19,8 @@
 #ifndef CPPCHECKLIBRARYDATA_H
 #define CPPCHECKLIBRARYDATA_H
 
+#include <cstdint>
+
 #include <QList>
 #include <QMap>
 #include <QPair>
@@ -72,7 +74,7 @@ class CppcheckLibraryData {
     struct Function {
         QString comments;
         QString name;
-        enum TrueFalseUnknown { False, True, Unknown } noreturn = Unknown;
+        enum TrueFalseUnknown : std::uint8_t { False, True, Unknown } noreturn = Unknown;
         bool gccPure{};
         bool gccConst{};
         bool leakignore{};
diff --git a/gui/mainwindow.h b/gui/mainwindow.h
index 5214b690ddca..7b3b164a9b0b 100644
--- a/gui/mainwindow.h
+++ b/gui/mainwindow.h
@@ -22,6 +22,8 @@
 #include "library.h"
 #include "platforms.h"
 
+#include <cstdint>
+
 #include <QFileDialog>
 #include <QMainWindow>
 #include <QObject>
@@ -62,7 +64,7 @@ class MainWindow : public QMainWindow {
     /**
      * @brief Maximum number of MRU project items in File-menu.
      */
-    enum { MaxRecentProjects = 5 };
+    enum : std::uint8_t { MaxRecentProjects = 5 };
 
     MainWindow(TranslationHandler* th, QSettings* settings);
     MainWindow(const MainWindow &) = delete;
diff --git a/gui/newsuppressiondialog.cpp b/gui/newsuppressiondialog.cpp
index 8635fc0ef0c1..7bd97431a848 100644
--- a/gui/newsuppressiondialog.cpp
+++ b/gui/newsuppressiondialog.cpp
@@ -31,7 +31,7 @@
 #include <QStringList>
 
 class QWidget;
-enum class Color;
+enum class Color : std::uint8_t ;
 
 NewSuppressionDialog::NewSuppressionDialog(QWidget *parent) :
     QDialog(parent),
diff --git a/gui/projectfile.h b/gui/projectfile.h
index df4d94fbbaa3..9e263e656495 100644
--- a/gui/projectfile.h
+++ b/gui/projectfile.h
@@ -23,6 +23,7 @@
 #include "suppressions.h"
 
 #include <cstddef>
+#include <cstdint>
 #include <map>
 #include <utility>
 
@@ -53,7 +54,7 @@ class ProjectFile : public QObject {
         if (this == mActiveProject) mActiveProject = nullptr;
     }
 
-    enum class CheckLevel {
+    enum class CheckLevel : std::uint8_t {
         normal,
         exhaustive
     };
diff --git a/gui/report.h b/gui/report.h
index 5cea9be508fc..12823d257809 100644
--- a/gui/report.h
+++ b/gui/report.h
@@ -19,6 +19,8 @@
 #ifndef REPORT_H
 #define REPORT_H
 
+#include <cstdint>
+
 #include <QFile>
 #include <QObject>
 #include <QString>
@@ -33,7 +35,7 @@ class ErrorItem;
  */
 class Report : public QObject {
 public:
-    enum Type {
+    enum Type : std::uint8_t {
         TXT,
         XMLV2,
         CSV,
diff --git a/gui/resultstree.h b/gui/resultstree.h
index 8d855766082c..96a40cb4d3c3 100644
--- a/gui/resultstree.h
+++ b/gui/resultstree.h
@@ -22,6 +22,8 @@
 
 #include "showtypes.h"
 
+#include <cstdint>
+
 #include <QObject>
 #include <QStandardItemModel>
 #include <QString>
@@ -39,7 +41,7 @@ class ThreadHandler;
 class QContextMenuEvent;
 class QKeyEvent;
 class QSettings;
-enum class Severity;
+enum class Severity : std::uint8_t;
 
 /// @addtogroup GUI
 /// @{
diff --git a/gui/showtypes.h b/gui/showtypes.h
index 605eaee17e1a..1d3829baa4d1 100644
--- a/gui/showtypes.h
+++ b/gui/showtypes.h
@@ -19,9 +19,11 @@
 #ifndef SHOWTYPES_H
 #define SHOWTYPES_H
 
+#include <cstdint>
+
 #include <QVariant>
 
-enum class Severity;
+enum class Severity : std::uint8_t;
 
 /// @addtogroup GUI
 /// @{
@@ -41,7 +43,7 @@ class ShowTypes {
     /**
      * @brief Show types we have (i.e. severities in the GUI).
      */
-    enum ShowType {
+    enum ShowType : std::uint8_t {
         ShowStyle = 0,
         ShowWarnings,
         ShowPerformance,
diff --git a/lib/analyzer.h b/lib/analyzer.h
index d6bcec727a7d..1b1a3074efd1 100644
--- a/lib/analyzer.h
+++ b/lib/analyzer.h
@@ -21,6 +21,8 @@
 
 #include "config.h"
 #include "mathlib.h"
+
+#include <cstdint>
 #include <string>
 #include <type_traits>
 #include <vector>
@@ -43,7 +45,7 @@ struct Analyzer {
         Action(T f) : mFlag(f) // cppcheck-suppress noExplicitConstructor
         {}
 
-        enum {
+        enum : std::uint16_t {
             None = 0,
             Read = (1 << 0),
             Write = (1 << 1),
@@ -130,7 +132,7 @@ struct Analyzer {
         unsigned int mFlag{};
     };
 
-    enum class Terminate { None, Bail, Escape, Modified, Inconclusive, Conditional };
+    enum class Terminate : std::uint8_t { None, Bail, Escape, Modified, Inconclusive, Conditional };
 
     struct Result {
         explicit Result(Action action = Action::None, Terminate terminate = Terminate::None)
@@ -146,10 +148,10 @@ struct Analyzer {
         }
     };
 
-    enum class Direction { Forward, Reverse };
+    enum class Direction : std::uint8_t { Forward, Reverse };
 
     struct Assume {
-        enum Flags {
+        enum Flags : std::uint8_t {
             None = 0,
             Quiet = (1 << 0),
             Absolute = (1 << 1),
@@ -157,7 +159,7 @@ struct Analyzer {
         };
     };
 
-    enum class Evaluate { Integral, ContainerEmpty };
+    enum class Evaluate : std::uint8_t { Integral, ContainerEmpty };
 
     /// Analyze a token
     virtual Action analyze(const Token* tok, Direction d) const = 0;
diff --git a/lib/astutils.h b/lib/astutils.h
index 10699f8de61d..929ad41cd438 100644
--- a/lib/astutils.h
+++ b/lib/astutils.h
@@ -22,6 +22,7 @@
 #define astutilsH
 //---------------------------------------------------------------------------
 
+#include <cstdint>
 #include <functional>
 #include <list>
 #include <stack>
@@ -39,7 +40,7 @@
 
 class Settings;
 
-enum class ChildrenToVisit {
+enum class ChildrenToVisit : std::uint8_t {
     none,
     op1,
     op2,
@@ -436,7 +437,7 @@ bool isConstVarExpression(const Token* tok, const std::function<bool(const Token
 
 bool isLeafDot(const Token* tok);
 
-enum class ExprUsage { None, NotUsed, PassedByReference, Used, Inconclusive };
+enum class ExprUsage : std::uint8_t { None, NotUsed, PassedByReference, Used, Inconclusive };
 
 ExprUsage getExprUsage(const Token* tok, int indirect, const Settings* settings);
 
diff --git a/lib/checkclass.cpp b/lib/checkclass.cpp
index 627f15574b75..f2474c8cd6dc 100644
--- a/lib/checkclass.cpp
+++ b/lib/checkclass.cpp
@@ -3075,7 +3075,7 @@ void CheckClass::duplInheritedMembersError(const Token *tok1, const Token* tok2,
 // Check that copy constructor and operator defined together
 //---------------------------------------------------------------------------
 
-enum class CtorType {
+enum class CtorType : std::uint8_t {
     NO,
     WITHOUT_BODY,
     WITH_BODY
diff --git a/lib/checkclass.h b/lib/checkclass.h
index 5a84e4cbdaf0..c1282e6a3a86 100644
--- a/lib/checkclass.h
+++ b/lib/checkclass.h
@@ -26,6 +26,7 @@
 #include "tokenize.h"
 #include "symboldatabase.h"
 
+#include <cstdint>
 #include <list>
 #include <map>
 #include <set>
@@ -292,7 +293,7 @@ class CPPCHECKLIB CheckClass : public Check {
     bool hasAllocation(const Function *func, const Scope* scope, const Token *start, const Token *end) const;
     bool hasAllocationInIfScope(const Function *func, const Scope* scope, const Token *ifStatementScopeStart) const;
     static bool hasAssignSelf(const Function *func, const Token *rhs, const Token **out_ifStatementScopeStart);
-    enum class Bool { TRUE, FALSE, BAILOUT };
+    enum class Bool : std::uint8_t { TRUE, FALSE, BAILOUT };
     static Bool isInverted(const Token *tok, const Token *rhs);
     static const Token * getIfStmtBodyStart(const Token *tok, const Token *rhs);
 
@@ -300,7 +301,7 @@ class CPPCHECKLIB CheckClass : public Check {
     bool isMemberVar(const Scope *scope, const Token *tok) const;
     static bool isMemberFunc(const Scope *scope, const Token *tok);
     static bool isConstMemberFunc(const Scope *scope, const Token *tok);
-    enum class MemberAccess { NONE, SELF, MEMBER };
+    enum class MemberAccess : std::uint8_t { NONE, SELF, MEMBER };
     bool checkConstFunc(const Scope *scope, const Function *func, MemberAccess& memberAccessed) const;
 
     // constructors helper function
diff --git a/lib/checkcondition.cpp b/lib/checkcondition.cpp
index f5e250a0cd80..aaeb9d2fa489 100644
--- a/lib/checkcondition.cpp
+++ b/lib/checkcondition.cpp
@@ -687,7 +687,7 @@ void CheckCondition::multiCondition2()
         });
 
         // parse until second condition is reached..
-        enum MULTICONDITIONTYPE { INNER, AFTER };
+        enum MULTICONDITIONTYPE : std::uint8_t { INNER, AFTER };
         const Token *tok;
 
         // Parse inner condition first and then early return condition
diff --git a/lib/checkio.cpp b/lib/checkio.cpp
index b4fc0a4abb62..f11dd8d34771 100644
--- a/lib/checkio.cpp
+++ b/lib/checkio.cpp
@@ -96,7 +96,7 @@ void CheckIO::coutCerrMisusageError(const Token* tok, const std::string& streamN
 // fopen("","r"); fwrite(); <- write to read-only file (or vice versa)
 // fclose(); fread(); <- Use closed file
 //---------------------------------------------------------------------------
-enum class OpenMode { CLOSED, READ_MODE, WRITE_MODE, RW_MODE, UNKNOWN_OM };
+enum class OpenMode : std::uint8_t { CLOSED, READ_MODE, WRITE_MODE, RW_MODE, UNKNOWN_OM };
 static OpenMode getMode(const std::string& str)
 {
     if (str.find('+', 1) != std::string::npos)
@@ -112,9 +112,9 @@ namespace {
     struct Filepointer {
         OpenMode mode;
         nonneg int mode_indent{};
-        enum class Operation {NONE, UNIMPORTANT, READ, WRITE, POSITIONING, OPEN, CLOSE, UNKNOWN_OP} lastOperation = Operation::NONE;
+        enum class Operation : std::uint8_t {NONE, UNIMPORTANT, READ, WRITE, POSITIONING, OPEN, CLOSE, UNKNOWN_OP} lastOperation = Operation::NONE;
         nonneg int op_indent{};
-        enum class AppendMode { UNKNOWN_AM, APPEND, APPEND_EX };
+        enum class AppendMode : std::uint8_t { UNKNOWN_AM, APPEND, APPEND_EX };
         AppendMode append_mode = AppendMode::UNKNOWN_AM;
         std::string filename;
         explicit Filepointer(OpenMode mode_ = OpenMode::UNKNOWN_OM)
diff --git a/lib/checkio.h b/lib/checkio.h
index cdc6b5e0e323..eba7c4e66e76 100644
--- a/lib/checkio.h
+++ b/lib/checkio.h
@@ -25,6 +25,7 @@
 #include "config.h"
 #include "tokenize.h"
 
+#include <cstdint>
 #include <ostream>
 #include <string>
 
@@ -33,7 +34,7 @@ class Settings;
 class Token;
 class Variable;
 class ErrorLogger;
-enum class Severity;
+enum class Severity : std::uint8_t;
 
 /// @addtogroup Checks
 /// @{
diff --git a/lib/checkleakautovar.cpp b/lib/checkleakautovar.cpp
index aee4e88ba6f6..eae2108d28aa 100644
--- a/lib/checkleakautovar.cpp
+++ b/lib/checkleakautovar.cpp
@@ -1134,7 +1134,7 @@ void CheckLeakAutoVar::ret(const Token *tok, VarInfo &varInfo, const bool isEndO
             // don't warn if we leave an inner scope
             if (isEndOfScope && var->scope() && tok != var->scope()->bodyEnd)
                 continue;
-            enum class PtrUsage { NONE, DEREF, PTR } used = PtrUsage::NONE;
+            enum class PtrUsage : std::uint8_t { NONE, DEREF, PTR } used = PtrUsage::NONE;
             for (const Token *tok2 = tok; tok2; tok2 = tok2->next()) {
                 if (tok2->str() == ";")
                     break;
diff --git a/lib/checkleakautovar.h b/lib/checkleakautovar.h
index 97aaff5722fb..946166fe91ca 100644
--- a/lib/checkleakautovar.h
+++ b/lib/checkleakautovar.h
@@ -27,6 +27,7 @@
 #include "library.h"
 #include "tokenize.h"
 
+#include <cstdint>
 #include <map>
 #include <set>
 #include <string>
@@ -38,7 +39,7 @@ class Token;
 
 class CPPCHECKLIB VarInfo {
 public:
-    enum AllocStatus { REALLOC = -3, OWNED = -2, DEALLOC = -1, NOALLOC = 0, ALLOC = 1 };
+    enum AllocStatus : std::int8_t { REALLOC = -3, OWNED = -2, DEALLOC = -1, NOALLOC = 0, ALLOC = 1 };
     struct AllocInfo {
         AllocStatus status;
         /** Allocation type. If it is a positive value then it corresponds to
@@ -54,7 +55,7 @@ class CPPCHECKLIB VarInfo {
             return status < 0;
         }
     };
-    enum Usage { USED, NORET };
+    enum Usage : std::uint8_t { USED, NORET };
     std::map<int, AllocInfo> alloctype;
     std::map<int, std::pair<const Token*, Usage>> possibleUsage;
     std::set<int> conditionalAlloc;
diff --git a/lib/checkmemoryleak.h b/lib/checkmemoryleak.h
index 0360d9dcc6c6..a77c05d0d976 100644
--- a/lib/checkmemoryleak.h
+++ b/lib/checkmemoryleak.h
@@ -36,6 +36,7 @@
 #include "config.h"
 #include "tokenize.h"
 
+#include <cstdint>
 #include <list>
 #include <string>
 
@@ -46,7 +47,7 @@ class Token;
 class Variable;
 class ErrorLogger;
 struct CWE;
-enum class Severity;
+enum class Severity : std::uint8_t;
 
 /// @addtogroup Core
 /// @{
@@ -92,7 +93,7 @@ class CPPCHECKLIB CheckMemoryLeak {
         : mTokenizer_(t), mErrorLogger_(e), mSettings_(s) {}
 
     /** @brief What type of allocation are used.. the "Many" means that several types of allocation and deallocation are used */
-    enum AllocType { No, Malloc, New, NewArray, File, Fd, Pipe, OtherMem, OtherRes, Many };
+    enum AllocType : std::uint8_t { No, Malloc, New, NewArray, File, Fd, Pipe, OtherMem, OtherRes, Many };
 
     void memoryLeak(const Token *tok, const std::string &varname, AllocType alloctype) const;
 
diff --git a/lib/checkother.cpp b/lib/checkother.cpp
index beff69966686..dc6d630954cd 100644
--- a/lib/checkother.cpp
+++ b/lib/checkother.cpp
@@ -1546,7 +1546,7 @@ void CheckOther::checkConstPointer()
             continue;
         pointers.emplace(var);
         const Token* parent = tok->astParent();
-        enum Deref { NONE, DEREF, MEMBER } deref = NONE;
+        enum Deref : std::uint8_t { NONE, DEREF, MEMBER } deref = NONE;
         bool hasIncDec = false;
         if (parent && (parent->isUnaryOp("*") || (hasIncDec = parent->isIncDecOp() && parent->astParent() && parent->astParent()->isUnaryOp("*"))))
             deref = DEREF;
diff --git a/lib/checkstl.cpp b/lib/checkstl.cpp
index 5eca694028fd..52d4ece35e64 100644
--- a/lib/checkstl.cpp
+++ b/lib/checkstl.cpp
@@ -1990,7 +1990,7 @@ void CheckStl::string_c_str()
         if (scope.type != Scope::eFunction || !scope.function)
             continue;
 
-        enum {charPtr, stdString, stdStringConstRef, Other} returnType = Other;
+        enum : std::uint8_t {charPtr, stdString, stdStringConstRef, Other} returnType = Other;
         if (Token::Match(scope.function->tokenDef->tokAt(-2), "char|wchar_t *"))
             returnType = charPtr;
         else if (Token::Match(scope.function->tokenDef->tokAt(-5), "const std :: string|wstring &"))
diff --git a/lib/checkstl.h b/lib/checkstl.h
index 15e265b0edd8..fdb137e0f6fd 100644
--- a/lib/checkstl.h
+++ b/lib/checkstl.h
@@ -28,6 +28,7 @@
 #include "tokenize.h"
 #include "vfvalue.h"
 
+#include <cstdint>
 #include <string>
 
 class Scope;
@@ -224,7 +225,7 @@ class CPPCHECKLIB CheckStl : public Check {
 
     void uselessCallsReturnValueError(const Token* tok, const std::string& varname, const std::string& function);
     void uselessCallsSwapError(const Token* tok, const std::string& varname);
-    enum class SubstrErrorType { EMPTY, COPY, PREFIX, PREFIX_CONCAT };
+    enum class SubstrErrorType : std::uint8_t { EMPTY, COPY, PREFIX, PREFIX_CONCAT };
     void uselessCallsSubstrError(const Token* tok, SubstrErrorType type);
     void uselessCallsEmptyError(const Token* tok);
     void uselessCallsRemoveError(const Token* tok, const std::string& function);
diff --git a/lib/checkuninitvar.h b/lib/checkuninitvar.h
index 025cc9f119f4..ab546d3f103d 100644
--- a/lib/checkuninitvar.h
+++ b/lib/checkuninitvar.h
@@ -29,6 +29,7 @@
 #include "tokenize.h"
 #include "vfvalue.h"
 
+#include <cstdint>
 #include <list>
 #include <map>
 #include <set>
@@ -69,7 +70,7 @@ class CPPCHECKLIB CheckUninitVar : public Check {
     /** @brief This constructor is used when registering the CheckUninitVar */
     CheckUninitVar() : Check(myName()) {}
 
-    enum Alloc { NO_ALLOC, NO_CTOR_CALL, CTOR_CALL, ARRAY };
+    enum Alloc : std::uint8_t { NO_ALLOC, NO_CTOR_CALL, CTOR_CALL, ARRAY };
 
     static const Token *isVariableUsage(const Token *vartok, const Library &library, bool pointer, Alloc alloc, int indirect = 0);
     const Token *isVariableUsage(const Token *vartok, bool pointer, Alloc alloc, int indirect = 0) const;
diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index 15f989d8a996..0d080af307e7 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -101,7 +101,7 @@ static bool isRaiiClass(const ValueType *valueType, bool cpp, bool defaultReturn
  */
 class Variables {
 public:
-    enum VariableType { standard, array, pointer, reference, pointerArray, referenceArray, pointerPointer, none };
+    enum VariableType : std::uint8_t { standard, array, pointer, reference, pointerArray, referenceArray, pointerPointer, none };
 
     /** Store information about variable usage */
     class VariableUsage {
diff --git a/lib/color.h b/lib/color.h
index 247de299200a..96ce2ac716ca 100644
--- a/lib/color.h
+++ b/lib/color.h
@@ -21,10 +21,11 @@
 
 #include "config.h"
 
+#include <cstdint>
 #include <ostream>
 #include <string>
 
-enum class Color {
+enum class Color : std::uint8_t {
     Reset      = 0,
     Bold       = 1,
     Dim        = 2,
diff --git a/lib/cppcheck.h b/lib/cppcheck.h
index ef68a9c4342b..9aef40dbee98 100644
--- a/lib/cppcheck.h
+++ b/lib/cppcheck.h
@@ -29,6 +29,7 @@
 #include "settings.h"
 
 #include <cstddef>
+#include <cstdint>
 #include <fstream>
 #include <functional>
 #include <list>
@@ -40,7 +41,7 @@
 #include <vector>
 
 class TokenList;
-enum class SHOWTIME_MODES;
+enum class SHOWTIME_MODES : std::uint8_t;
 struct FileSettings;
 class CheckUnusedFunctions;
 
diff --git a/lib/ctu.h b/lib/ctu.h
index 28e4421871c4..a5839251d1ea 100644
--- a/lib/ctu.h
+++ b/lib/ctu.h
@@ -28,6 +28,7 @@
 #include "mathlib.h"
 #include "vfvalue.h"
 
+#include <cstdint>
 #include <list>
 #include <map>
 #include <string>
@@ -51,7 +52,7 @@ namespace tinyxml2 {
 namespace CTU {
     class CPPCHECKLIB FileInfo : public Check::FileInfo {
     public:
-        enum class InvalidValueType { null, uninit, bufferOverflow };
+        enum class InvalidValueType : std::uint8_t { null, uninit, bufferOverflow };
 
         std::string toString() const override;
 
diff --git a/lib/errortypes.h b/lib/errortypes.h
index 3e9a6a41426e..0a13030c9f1f 100644
--- a/lib/errortypes.h
+++ b/lib/errortypes.h
@@ -23,6 +23,7 @@
 
 #include "config.h"
 
+#include <cstdint>
 #include <stdexcept>
 #include <list>
 #include <string>
@@ -34,7 +35,7 @@ class Token;
 
 /** @brief Simple container to be thrown when internal error is detected. */
 struct CPPCHECKLIB InternalError {
-    enum Type {AST, SYNTAX, UNKNOWN_MACRO, INTERNAL, LIMIT, INSTANTIATION};
+    enum Type : std::uint8_t {AST, SYNTAX, UNKNOWN_MACRO, INTERNAL, LIMIT, INSTANTIATION};
 
     InternalError(const Token *tok, std::string errorMsg, Type type = INTERNAL);
     InternalError(const Token *tok, std::string errorMsg, std::string details, Type type = INTERNAL);
@@ -51,16 +52,16 @@ class TerminateException : public std::runtime_error {
     TerminateException() : std::runtime_error("terminate") {}
 };
 
-enum class Certainty {
+enum class Certainty : std::uint8_t {
     normal, inconclusive
 };
 
-enum class Checks {
+enum class Checks : std::uint8_t {
     unusedFunction, missingInclude, internalCheck
 };
 
 /** @brief enum class for severity. Used when reporting errors. */
-enum class Severity {
+enum class Severity : std::uint8_t {
     /**
      * No severity (default value).
      */
diff --git a/lib/forwardanalyzer.cpp b/lib/forwardanalyzer.cpp
index 92eedbe5098d..0680769c4f34 100644
--- a/lib/forwardanalyzer.cpp
+++ b/lib/forwardanalyzer.cpp
@@ -45,8 +45,8 @@
 
 namespace {
     struct ForwardTraversal {
-        enum class Progress { Continue, Break, Skip };
-        enum class Terminate { None, Bail, Inconclusive };
+        enum class Progress : std::uint8_t { Continue, Break, Skip };
+        enum class Terminate : std::uint8_t { None, Bail, Inconclusive };
         ForwardTraversal(const ValuePtr<Analyzer>& analyzer, const TokenList& tokenList, ErrorLogger* const errorLogger, const Settings& settings)
             : analyzer(analyzer), tokenList(tokenList), errorLogger(errorLogger), settings(settings)
         {}
@@ -327,7 +327,7 @@ namespace {
             return r;
         }
 
-        enum class Status {
+        enum class Status : std::uint8_t {
             None,
             Inconclusive,
         };
diff --git a/lib/fwdanalysis.h b/lib/fwdanalysis.h
index 17fc29f7b42c..9b612eb4cafb 100644
--- a/lib/fwdanalysis.h
+++ b/lib/fwdanalysis.h
@@ -23,6 +23,7 @@
 
 #include "config.h"
 
+#include <cstdint>
 #include <set>
 #include <vector>
 
@@ -73,7 +74,7 @@ class FwdAnalysis {
 
     /** Result of forward analysis */
     struct Result {
-        enum class Type { NONE, READ, WRITE, BREAK, RETURN, BAILOUT } type;
+        enum class Type : std::uint8_t { NONE, READ, WRITE, BREAK, RETURN, BAILOUT } type;
         explicit Result(Type type) : type(type) {}
         Result(Type type, const Token *token) : type(type), token(token) {}
         const Token* token{};
@@ -83,7 +84,7 @@ class FwdAnalysis {
     Result checkRecursive(const Token *expr, const Token *startToken, const Token *endToken, const std::set<nonneg int> &exprVarIds, bool local, bool inInnerClass, int depth=0);
 
     const Library &mLibrary;
-    enum class What { Reassign, UnusedValue, ValueFlow } mWhat = What::Reassign;
+    enum class What : std::uint8_t { Reassign, UnusedValue, ValueFlow } mWhat = What::Reassign;
     std::vector<KnownAndToken> mValueFlow;
     bool mValueFlowKnown = true;
 };
diff --git a/lib/importproject.cpp b/lib/importproject.cpp
index 754dcb812d83..b085f05f3dbc 100644
--- a/lib/importproject.cpp
+++ b/lib/importproject.cpp
@@ -498,7 +498,7 @@ namespace {
         }
         std::string name;
         std::string configuration;
-        enum { Win32, x64, Unknown } platform = Unknown;
+        enum : std::uint8_t { Win32, x64, Unknown } platform = Unknown;
         std::string platformStr;
     };
 
diff --git a/lib/importproject.h b/lib/importproject.h
index 54a8f6f0cd20..01ce274ec571 100644
--- a/lib/importproject.h
+++ b/lib/importproject.h
@@ -26,6 +26,7 @@
 #include "platform.h"
 #include "utils.h"
 
+#include <cstdint>
 #include <iosfwd>
 #include <list>
 #include <map>
@@ -51,7 +52,7 @@ class Settings;
  */
 class CPPCHECKLIB WARN_UNUSED ImportProject {
 public:
-    enum class Type {
+    enum class Type : std::uint8_t {
         NONE,
         UNKNOWN,
         MISSING,
diff --git a/lib/library.h b/lib/library.h
index 11d59c676cde..fcc25eccbca9 100644
--- a/lib/library.h
+++ b/lib/library.h
@@ -25,6 +25,7 @@
 #include "mathlib.h"
 #include "standards.h"
 
+#include <cstdint>
 #include <map>
 #include <memory>
 #include <set>
@@ -36,7 +37,7 @@
 
 class Token;
 class Settings;
-enum class Severity;
+enum class Severity : std::uint8_t;
 
 namespace tinyxml2 {
     class XMLDocument;
@@ -59,7 +60,7 @@ class CPPCHECKLIB Library {
 public:
     Library() = default;
 
-    enum class ErrorCode {
+    enum class ErrorCode : std::uint8_t {
         OK,
         FILE_NOT_FOUND, BAD_XML, UNKNOWN_ELEMENT, MISSING_ATTRIBUTE, BAD_ATTRIBUTE_VALUE,
         UNSUPPORTED_FORMAT, DUPLICATE_PLATFORM_TYPE, PLATFORM_TYPE_REDEFINED, DUPLICATE_DEFINE
@@ -81,7 +82,7 @@ class CPPCHECKLIB Library {
     struct AllocFunc {
         int groupId;
         int arg;
-        enum class BufferSize {none,malloc,calloc,strdup};
+        enum class BufferSize : std::uint8_t {none,malloc,calloc,strdup};
         BufferSize bufferSize;
         int bufferSizeArg1;
         int bufferSizeArg2;
@@ -178,7 +179,7 @@ class CPPCHECKLIB Library {
     bool isNotLibraryFunction(const Token *ftok) const;
     bool matchArguments(const Token *ftok, const std::string &functionName) const;
 
-    enum class UseRetValType { NONE, DEFAULT, ERROR_CODE };
+    enum class UseRetValType : std::uint8_t { NONE, DEFAULT, ERROR_CODE };
     UseRetValType getUseRetValType(const Token* ftok) const;
 
     const std::string& returnValue(const Token *ftok) const;
@@ -195,7 +196,7 @@ class CPPCHECKLIB Library {
     public:
         Container() = default;
 
-        enum class Action {
+        enum class Action : std::uint8_t {
             RESIZE,
             CLEAR,
             PUSH,
@@ -209,7 +210,7 @@ class CPPCHECKLIB Library {
             CHANGE_INTERNAL,
             NO_ACTION
         };
-        enum class Yield {
+        enum class Yield : std::uint8_t {
             AT_INDEX,
             ITEM,
             BUFFER,
@@ -290,7 +291,7 @@ class CPPCHECKLIB Library {
         IteratorInfo iteratorInfo;
 
         struct MinSize {
-            enum class Type { NONE, STRLEN, ARGVALUE, SIZEOF, MUL, VALUE };
+            enum class Type : std::uint8_t { NONE, STRLEN, ARGVALUE, SIZEOF, MUL, VALUE };
             MinSize(Type t, int a) : type(t), arg(a) {}
             Type type;
             int arg;
@@ -300,7 +301,7 @@ class CPPCHECKLIB Library {
         };
         std::vector<MinSize> minsizes;
 
-        enum class Direction {
+        enum class Direction : std::uint8_t {
             DIR_IN,     ///< Input to called function. Data is treated as read-only.
             DIR_OUT,    ///< Output to caller. Data is passed by reference or address and is potentially written.
             DIR_INOUT,  ///< Input to called function, and output to caller. Data is passed by reference or address and is potentially modified.
@@ -441,7 +442,7 @@ class CPPCHECKLIB Library {
     struct PodType {
         unsigned int size;
         char sign;
-        enum class Type { NO, BOOL, CHAR, SHORT, INT, LONG, LONGLONG } stdtype;
+        enum class Type : std::uint8_t { NO, BOOL, CHAR, SHORT, INT, LONG, LONGLONG } stdtype;
     };
     const PodType *podtype(const std::string &name) const {
         const std::unordered_map<std::string, PodType>::const_iterator it = mPodTypes.find(name);
@@ -498,7 +499,7 @@ class CPPCHECKLIB Library {
     static bool isContainerYield(const Token * const cond, Library::Container::Yield y, const std::string& fallback=emptyString);
 
     /** Suppress/check a type */
-    enum class TypeCheck { def,
+    enum class TypeCheck : std::uint8_t { def,
                            check,
                            suppress,
                            checkFiniteLifetime, // (unusedvar) object has side effects, but immediate destruction is wrong
@@ -564,7 +565,7 @@ class CPPCHECKLIB Library {
         int mOffset{};
         std::set<std::string> mBlocks;
     };
-    enum class FalseTrueMaybe { False, True, Maybe };
+    enum class FalseTrueMaybe : std::uint8_t { False, True, Maybe };
     int mAllocId{};
     std::set<std::string> mFiles;
     std::map<std::string, AllocFunc> mAlloc; // allocation functions
@@ -599,7 +600,7 @@ class CPPCHECKLIB Library {
         return (it == data.end()) ? nullptr : &it->second;
     }
 
-    enum DetectContainer { ContainerOnly, IteratorOnly, Both };
+    enum DetectContainer : std::uint8_t { ContainerOnly, IteratorOnly, Both };
     const Library::Container* detectContainerInternal(const Token* typeStart, DetectContainer detect, bool* isIterator = nullptr, bool withoutStd = false) const;
 };
 
diff --git a/lib/mathlib.cpp b/lib/mathlib.cpp
index b56fdc07e0f2..242d6ef2cef9 100644
--- a/lib/mathlib.cpp
+++ b/lib/mathlib.cpp
@@ -541,7 +541,7 @@ bool MathLib::isDecimalFloat(const std::string &str)
 {
     if (str.empty())
         return false;
-    enum class State {
+    enum class State : std::uint8_t {
         START, BASE_DIGITS1, LEADING_DECIMAL, TRAILING_DECIMAL, BASE_DIGITS2, E, MANTISSA_PLUSMINUS, MANTISSA_DIGITS, SUFFIX_F, SUFFIX_L, SUFFIX_LITERAL_LEADER, SUFFIX_LITERAL
     } state = State::START;
     std::string::const_iterator it = str.cbegin();
@@ -649,7 +649,7 @@ bool MathLib::isPositive(const std::string &str)
 
 static bool isValidIntegerSuffixIt(std::string::const_iterator it, std::string::const_iterator end, bool supportMicrosoftExtensions=true)
 {
-    enum class Status { START, SUFFIX_U, SUFFIX_UL, SUFFIX_ULL, SUFFIX_UZ, SUFFIX_L, SUFFIX_LU, SUFFIX_LL, SUFFIX_LLU, SUFFIX_I, SUFFIX_I6, SUFFIX_I64, SUFFIX_UI, SUFFIX_UI6, SUFFIX_UI64, SUFFIX_Z, SUFFIX_LITERAL_LEADER, SUFFIX_LITERAL } state = Status::START;
+    enum class Status : std::uint8_t { START, SUFFIX_U, SUFFIX_UL, SUFFIX_ULL, SUFFIX_UZ, SUFFIX_L, SUFFIX_LU, SUFFIX_LL, SUFFIX_LLU, SUFFIX_I, SUFFIX_I6, SUFFIX_I64, SUFFIX_UI, SUFFIX_UI6, SUFFIX_UI64, SUFFIX_Z, SUFFIX_LITERAL_LEADER, SUFFIX_LITERAL } state = Status::START;
     for (; it != end; ++it) {
         switch (state) {
         case Status::START:
@@ -770,7 +770,7 @@ bool MathLib::isValidIntegerSuffix(const std::string& str, bool supportMicrosoft
  **/
 bool MathLib::isOct(const std::string& str)
 {
-    enum class Status {
+    enum class Status : std::uint8_t {
         START, OCTAL_PREFIX, DIGITS
     } state = Status::START;
     if (str.empty())
@@ -805,7 +805,7 @@ bool MathLib::isOct(const std::string& str)
 
 bool MathLib::isIntHex(const std::string& str)
 {
-    enum class Status {
+    enum class Status : std::uint8_t {
         START, HEX_0, HEX_X, DIGIT
     } state = Status::START;
     if (str.empty())
@@ -846,7 +846,7 @@ bool MathLib::isIntHex(const std::string& str)
 
 bool MathLib::isFloatHex(const std::string& str)
 {
-    enum class Status {
+    enum class Status : std::uint8_t {
         START, HEX_0, HEX_X, WHOLE_NUMBER_DIGIT, POINT, FRACTION, EXPONENT_P, EXPONENT_SIGN, EXPONENT_DIGITS, EXPONENT_SUFFIX
     } state = Status::START;
     if (str.empty())
@@ -936,7 +936,7 @@ bool MathLib::isFloatHex(const std::string& str)
  **/
 bool MathLib::isBin(const std::string& str)
 {
-    enum class Status {
+    enum class Status : std::uint8_t {
         START, GNU_BIN_PREFIX_0, GNU_BIN_PREFIX_B, DIGIT
     } state = Status::START;
     if (str.empty())
@@ -977,7 +977,7 @@ bool MathLib::isBin(const std::string& str)
 
 bool MathLib::isDec(const std::string & str)
 {
-    enum class Status {
+    enum class Status : std::uint8_t {
         START, DIGIT
     } state = Status::START;
     if (str.empty())
diff --git a/lib/mathlib.h b/lib/mathlib.h
index 795250feaf1a..5a3ec0c5f69c 100644
--- a/lib/mathlib.h
+++ b/lib/mathlib.h
@@ -23,6 +23,7 @@
 
 #include "config.h"
 
+#include <cstdint>
 #include <string>
 
 /// @addtogroup Core
@@ -39,7 +40,7 @@ class CPPCHECKLIB MathLib {
     private:
         long long mIntValue{};
         double mDoubleValue{};
-        enum class Type { INT, LONG, LONGLONG, FLOAT } mType;
+        enum class Type : std::uint8_t { INT, LONG, LONGLONG, FLOAT } mType;
         bool mIsUnsigned{};
 
         void promote(const value &v);
diff --git a/lib/pathanalysis.h b/lib/pathanalysis.h
index 94c3318a8269..d0415873be51 100644
--- a/lib/pathanalysis.h
+++ b/lib/pathanalysis.h
@@ -21,6 +21,7 @@
 
 #include "errortypes.h"
 
+#include <cstdint>
 #include <functional>
 #include <list>
 #include <utility>
@@ -30,7 +31,7 @@ class Scope;
 class Token;
 
 struct PathAnalysis {
-    enum class Progress {
+    enum class Progress : std::uint8_t {
         Continue,
         Break
     };
diff --git a/lib/platform.h b/lib/platform.h
index 5e4e51e71f60..7f0f48e1a80a 100644
--- a/lib/platform.h
+++ b/lib/platform.h
@@ -25,6 +25,7 @@
 #include "standards.h"
 
 #include <climits>
+#include <cstdint>
 #include <stdexcept>
 #include <string>
 #include <vector>
@@ -102,7 +103,7 @@ class CPPCHECKLIB Platform {
 
     char defaultSign;  // unsigned:'u', signed:'s', unknown:'\0'
 
-    enum Type {
+    enum Type : std::uint8_t {
         Unspecified, // No platform specified
         Native, // whatever system this code was compiled on
         Win32A,
diff --git a/lib/preprocessor.h b/lib/preprocessor.h
index a902e1e953e6..15fb180b258e 100644
--- a/lib/preprocessor.h
+++ b/lib/preprocessor.h
@@ -24,6 +24,7 @@
 #include "config.h"
 
 #include <cstddef>
+#include <cstdint>
 #include <istream>
 #include <list>
 #include <map>
@@ -80,7 +81,7 @@ class CPPCHECKLIB Preprocessor {
     /**
      * Include file types.
      */
-    enum HeaderTypes {
+    enum HeaderTypes : std::uint8_t {
         UserHeader = 1,
         SystemHeader
     };
diff --git a/lib/settings.h b/lib/settings.h
index a4aa03eee46b..ed6fc4b28497 100644
--- a/lib/settings.h
+++ b/lib/settings.h
@@ -43,7 +43,7 @@
 #include <unordered_set>
 #include <utility>
 
-enum class SHOWTIME_MODES;
+enum class SHOWTIME_MODES : std::uint8_t;
 namespace ValueFlow {
     class Value;
 }
@@ -195,7 +195,7 @@ class CPPCHECKLIB WARN_UNUSED Settings {
     bool exceptionHandling{};
 #endif
 
-    enum class ExecutorType
+    enum class ExecutorType : std::uint8_t
     {
 #ifdef HAS_THREADING_MODEL_THREAD
         Thread,
@@ -466,7 +466,7 @@ class CPPCHECKLIB WARN_UNUSED Settings {
     void setCheckLevelExhaustive();
     void setCheckLevelNormal();
 
-    enum class CheckLevel {
+    enum class CheckLevel : std::uint8_t {
         exhaustive,
         normal
     };
diff --git a/lib/standards.h b/lib/standards.h
index 4b1469164ca5..8cf4cd5458ca 100644
--- a/lib/standards.h
+++ b/lib/standards.h
@@ -23,6 +23,7 @@
 
 #include "utils.h"
 
+#include <cstdint>
 #include <string>
 
 /// @addtogroup Core
@@ -34,13 +35,13 @@
  * This struct contains all possible standards that cppcheck recognize.
  */
 struct Standards {
-    enum Language { None, C, CPP };
+    enum Language : std::uint8_t { None, C, CPP };
 
     /** C code standard */
-    enum cstd_t { C89, C99, C11, CLatest = C11 } c = CLatest;
+    enum cstd_t : std::uint8_t { C89, C99, C11, CLatest = C11 } c = CLatest;
 
     /** C++ code standard */
-    enum cppstd_t { CPP03, CPP11, CPP14, CPP17, CPP20, CPP23, CPPLatest = CPP23 } cpp = CPPLatest;
+    enum cppstd_t : std::uint8_t { CPP03, CPP11, CPP14, CPP17, CPP20, CPP23, CPPLatest = CPP23 } cpp = CPPLatest;
 
     /** --std value given on command line */
     std::string stdValue;
diff --git a/lib/suppressions.h b/lib/suppressions.h
index bf50e5891c78..26262621706a 100644
--- a/lib/suppressions.h
+++ b/lib/suppressions.h
@@ -23,6 +23,7 @@
 #include "config.h"
 
 #include <cstddef>
+#include <cstdint>
 #include <istream>
 #include <list>
 #include <set>
@@ -36,13 +37,13 @@
 class Tokenizer;
 class ErrorMessage;
 class ErrorLogger;
-enum class Certainty;
+enum class Certainty : std::uint8_t;
 
 /** @brief class for handling suppressions */
 class CPPCHECKLIB SuppressionList {
 public:
 
-    enum class Type {
+    enum class Type : std::uint8_t {
         unique, file, block, blockBegin, blockEnd, macro
     };
 
@@ -147,7 +148,7 @@ class CPPCHECKLIB SuppressionList {
         bool matched{};
         bool checked{}; // for inline suppressions, checked or not
 
-        enum { NO_LINE = -1 };
+        enum : std::int8_t { NO_LINE = -1 };
     };
 
     /**
diff --git a/lib/symboldatabase.h b/lib/symboldatabase.h
index ffa0777ecf59..ac6171e8ee4a 100644
--- a/lib/symboldatabase.h
+++ b/lib/symboldatabase.h
@@ -31,6 +31,7 @@
 
 #include <algorithm>
 #include <cctype>
+#include <cstdint>
 #include <iosfwd>
 #include <list>
 #include <map>
@@ -51,7 +52,7 @@ class ValueType;
 /**
  * @brief Access control enumerations.
  */
-enum class AccessControl { Public, Protected, Private, Global, Namespace, Argument, Local, Throw };
+enum class AccessControl : std::uint8_t { Public, Protected, Private, Global, Namespace, Argument, Local, Throw };
 
 /**
  * @brief Array dimension information.
@@ -68,7 +69,7 @@ class CPPCHECKLIB Type {
     const Token* classDef;     ///< Points to "class" token
     const Scope* classScope;
     const Scope* enclosingScope;
-    enum class NeedInitialization {
+    enum class NeedInitialization : std::uint8_t {
         Unknown, True, False
     } needInitialization = NeedInitialization::Unknown;
 
@@ -747,7 +748,7 @@ class CPPCHECKLIB Function {
     }
 
 public:
-    enum Type { eConstructor, eCopyConstructor, eMoveConstructor, eOperatorEqual, eDestructor, eFunction, eLambda };
+    enum Type : std::uint8_t { eConstructor, eCopyConstructor, eMoveConstructor, eOperatorEqual, eDestructor, eFunction, eLambda };
 
     Function(const Token *tok, const Scope *scope, const Token *tokDef, const Token *tokArgDef);
     Function(const Token *tokenDef, const std::string &clangType);
@@ -1021,7 +1022,7 @@ class CPPCHECKLIB Scope {
         const Scope *scope;
     };
 
-    enum ScopeType { eGlobal, eClass, eStruct, eUnion, eNamespace, eFunction, eIf, eElse, eFor, eWhile, eDo, eSwitch, eUnconditional, eTry, eCatch, eLambda, eEnum };
+    enum ScopeType : std::uint8_t { eGlobal, eClass, eStruct, eUnion, eNamespace, eFunction, eIf, eElse, eFor, eWhile, eDo, eSwitch, eUnconditional, eTry, eCatch, eLambda, eEnum };
 
     Scope(const SymbolDatabase *check_, const Token *classDef_, const Scope *nestedIn_);
     Scope(const SymbolDatabase *check_, const Token *classDef_, const Scope *nestedIn_, ScopeType type_, const Token *start_);
@@ -1198,7 +1199,7 @@ class CPPCHECKLIB Scope {
     void getVariableList(const Settings& settings, const Token *start, const Token *end);
 };
 
-enum class Reference {
+enum class Reference : std::uint8_t {
     None,
     LValue,
     RValue
@@ -1207,8 +1208,8 @@ enum class Reference {
 /** Value type */
 class CPPCHECKLIB ValueType {
 public:
-    enum Sign { UNKNOWN_SIGN, SIGNED, UNSIGNED } sign = UNKNOWN_SIGN;
-    enum Type {
+    enum Sign : std::uint8_t { UNKNOWN_SIGN, SIGNED, UNSIGNED } sign = UNKNOWN_SIGN;
+    enum Type : std::uint8_t {
         UNKNOWN_TYPE,
         POD,
         NONSTD,
@@ -1278,7 +1279,7 @@ class CPPCHECKLIB ValueType {
 
     static Type typeFromString(const std::string &typestr, bool longType);
 
-    enum class MatchResult { UNKNOWN, SAME, FALLBACK1, FALLBACK2, NOMATCH };
+    enum class MatchResult : std::uint8_t { UNKNOWN, SAME, FALLBACK1, FALLBACK2, NOMATCH };
     static MatchResult matchParameter(const ValueType *call, const ValueType *func);
     static MatchResult matchParameter(const ValueType *call, const Variable *callVar, const Variable *funcVar);
 
diff --git a/lib/templatesimplifier.h b/lib/templatesimplifier.h
index e8e77507e5ed..c5ba74a8ddfc 100644
--- a/lib/templatesimplifier.h
+++ b/lib/templatesimplifier.h
@@ -24,6 +24,7 @@
 
 #include "config.h"
 
+#include <cstdint>
 #include <ctime>
 #include <list>
 #include <map>
@@ -77,7 +78,7 @@ class CPPCHECKLIB TemplateSimplifier {
         const Token *mParamEnd;
         unsigned int mFlags;
 
-        enum {
+        enum : std::uint16_t {
             fIsClass                 = (1 << 0), // class template
             fIsFunction              = (1 << 1), // function template
             fIsVariable              = (1 << 2), // variable template
diff --git a/lib/timer.h b/lib/timer.h
index a42f72b57a9a..28d3dffdac5b 100644
--- a/lib/timer.h
+++ b/lib/timer.h
@@ -22,12 +22,13 @@
 
 #include "config.h"
 
+#include <cstdint>
 #include <ctime>
 #include <map>
 #include <mutex>
 #include <string>
 
-enum class SHOWTIME_MODES {
+enum class SHOWTIME_MODES : std::uint8_t {
     SHOWTIME_NONE,
     SHOWTIME_FILE,
     SHOWTIME_FILE_TOTAL,
diff --git a/lib/token.h b/lib/token.h
index 4c5ceaba1112..0573425bf2e1 100644
--- a/lib/token.h
+++ b/lib/token.h
@@ -57,7 +57,7 @@ struct ScopeInfo2 {
     std::set<std::string> usingNamespaces;
 };
 
-enum class TokenDebug { None, ValueFlow, ValueType };
+enum class TokenDebug : std::uint8_t { None, ValueFlow, ValueType };
 
 struct TokenImpl {
     nonneg int mVarId{};
@@ -115,14 +115,14 @@ struct TokenImpl {
 
     // __cppcheck_in_range__
     struct CppcheckAttributes {
-        enum Type { LOW, HIGH } type = LOW;
+        enum Type : std::uint8_t { LOW, HIGH } type = LOW;
         MathLib::bigint value{};
         CppcheckAttributes* next{};
     };
     CppcheckAttributes* mCppcheckAttributes{};
 
     // For memoization, to speed up parsing of huge arrays #8897
-    enum class Cpp11init { UNKNOWN, CPP11INIT, NOINIT } mCpp11init = Cpp11init::UNKNOWN;
+    enum class Cpp11init : std::uint8_t { UNKNOWN, CPP11INIT, NOINIT } mCpp11init = Cpp11init::UNKNOWN;
 
     TokenDebug mDebug{};
 
@@ -157,7 +157,7 @@ class CPPCHECKLIB Token {
     Token(const Token &) = delete;
     Token& operator=(const Token &) = delete;
 
-    enum Type {
+    enum Type : std::uint8_t {
         eVariable, eType, eFunction, eKeyword, eName, // Names: Variable (varId), Type (typeId, later), Function (FuncId, later), Language keyword, Name (unknown identifier)
         eNumber, eString, eChar, eBoolean, eLiteral, eEnumerator, // Literals: Number, String, Character, Boolean, User defined literal (C++11), Enumerator
         eArithmeticalOp, eComparisonOp, eAssignmentOp, eLogicalOp, eBitOp, eIncDecOp, eExtendedOp, // Operators: Arithmetical, Comparison, Assignment, Logical, Bitwise, ++/--, Extended
@@ -1328,7 +1328,7 @@ class CPPCHECKLIB Token {
         fIsInitComma            = (1ULL << 42), // Is this comma located inside some {..}. i.e: {1,2,3,4}
     };
 
-    enum : uint64_t {
+    enum : std::uint8_t  {
         efMaxSize = sizeof(nonneg int) * 8,
         efIsUnique = efMaxSize - 2,
     };
diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 09937458b189..096a65dbd4bf 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -2387,7 +2387,7 @@ void Tokenizer::simplifyTypedefCpp()
 
 namespace {
     struct ScopeInfo3 {
-        enum Type { Global, Namespace, Record, MemberFunction, Other };
+        enum Type : std::uint8_t { Global, Namespace, Record, MemberFunction, Other };
         ScopeInfo3() : parent(nullptr), type(Global), bodyStart(nullptr), bodyEnd(nullptr) {}
         ScopeInfo3(ScopeInfo3 *parent_, Type type_, std::string name_, const Token *bodyStart_, const Token *bodyEnd_)
             : parent(parent_), type(type_), name(std::move(name_)), bodyStart(bodyStart_), bodyEnd(bodyEnd_) {
diff --git a/lib/tokenize.h b/lib/tokenize.h
index de8b6e8a1bc6..8c8df85e2db7 100644
--- a/lib/tokenize.h
+++ b/lib/tokenize.h
@@ -24,6 +24,7 @@
 #include "config.h"
 #include "tokenlist.h"
 
+#include <cstdint>
 #include <iosfwd>
 #include <list>
 #include <map>
@@ -37,7 +38,7 @@ class Token;
 class TemplateSimplifier;
 class ErrorLogger;
 class Preprocessor;
-enum class Severity;
+enum class Severity : std::uint8_t;
 
 /// @addtogroup Core
 /// @{
diff --git a/lib/tokenlist.cpp b/lib/tokenlist.cpp
index b7cf98583632..6a64889cc5e1 100644
--- a/lib/tokenlist.cpp
+++ b/lib/tokenlist.cpp
@@ -1926,7 +1926,7 @@ void TokenList::simplifyPlatformTypes()
 
     const bool isCPP11 = isCPP() && (mSettings->standards.cpp >= Standards::CPP11);
 
-    enum { isLongLong, isLong, isInt } type;
+    enum : std::uint8_t { isLongLong, isLong, isInt } type;
 
     /** @todo This assumes a flat address space. Not true for segmented address space (FAR *). */
 
diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 9876461df2c4..13549a6899bc 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -3407,7 +3407,7 @@ struct MemberExpressionAnalyzer : SubExpressionAnalyzer {
     }
 };
 
-enum class LifetimeCapture { Undefined, ByValue, ByReference };
+enum class LifetimeCapture : std::uint8_t { Undefined, ByValue, ByReference };
 
 static std::string lifetimeType(const Token *tok, const ValueFlow::Value *val)
 {
diff --git a/lib/vfvalue.h b/lib/vfvalue.h
index b3a7598cbedd..8abecac2a06e 100644
--- a/lib/vfvalue.h
+++ b/lib/vfvalue.h
@@ -26,6 +26,7 @@
 
 #include <cassert>
 #include <cmath>
+#include <cstdint>
 #include <functional>
 #include <list>
 #include <string>
@@ -41,7 +42,7 @@ namespace ValueFlow
     public:
         using ErrorPathItem = std::pair<const Token *, std::string>;
         using ErrorPath = std::list<ErrorPathItem>;
-        enum class Bound { Upper, Lower, Point };
+        enum class Bound : std::uint8_t { Upper, Lower, Point };
 
         explicit Value(long long val = 0, Bound b = Bound::Point) :
             bound(b),
@@ -195,7 +196,7 @@ namespace ValueFlow
 
         std::string toString() const;
 
-        enum class ValueType {
+        enum class ValueType : std::uint8_t {
             INT,
             TOK,
             FLOAT,
@@ -301,7 +302,7 @@ namespace ValueFlow
         int indirect{};
 
         /** kind of moved  */
-        enum class MoveKind { NonMovedVariable, MovedVariable, ForwardedVariable } moveKind = MoveKind::NonMovedVariable;
+        enum class MoveKind : std::uint8_t { NonMovedVariable, MovedVariable, ForwardedVariable } moveKind = MoveKind::NonMovedVariable;
 
         /** Path id */
         MathLib::bigint path{};
@@ -314,7 +315,7 @@ namespace ValueFlow
         // Set to where a lifetime is captured by value
         const Token* capturetok{};
 
-        enum class LifetimeKind {
+        enum class LifetimeKind : std::uint8_t {
             // Pointer points to a member of lifetime
             Object,
             // A member of object points to the lifetime
@@ -327,7 +328,7 @@ namespace ValueFlow
             Address
         } lifetimeKind = LifetimeKind::Object;
 
-        enum class LifetimeScope { Local, Argument, SubFunction, ThisPointer, ThisValue } lifetimeScope = LifetimeScope::Local;
+        enum class LifetimeScope : std::uint8_t { Local, Argument, SubFunction, ThisPointer, ThisValue } lifetimeScope = LifetimeScope::Local;
 
         static const char* toString(MoveKind moveKind);
         static const char* toString(LifetimeKind lifetimeKind);
@@ -335,7 +336,7 @@ namespace ValueFlow
         static const char* toString(Bound bound);
 
         /** How known is this value */
-        enum class ValueKind {
+        enum class ValueKind : std::uint8_t {
             /** This value is possible, other unlisted values may also be possible */
             Possible,
             /** Only listed values are possible */
diff --git a/test/fixture.h b/test/fixture.h
index af2276093630..d4dec6605dfb 100644
--- a/test/fixture.h
+++ b/test/fixture.h
@@ -40,8 +40,8 @@
 
 class options;
 class Tokenizer;
-enum class Certainty;
-enum class Severity;
+enum class Certainty : std::uint8_t;
+enum class Severity : std::uint8_t;
 
 class TestFixture : public ErrorLogger {
 private:
diff --git a/test/testastutils.cpp b/test/testastutils.cpp
index 9140b16e5610..010072164f0a 100644
--- a/test/testastutils.cpp
+++ b/test/testastutils.cpp
@@ -453,7 +453,7 @@ class TestAstUtils : public TestFixture {
         ASSERT_EQUALS(true, nextAfterAstRightmostLeaf("int * g(int); void f(int a, int b) { int x = g(a + 1)[b]; }", "+", ") ["));
     }
 
-    enum class Result {False, True, Fail};
+    enum class Result : std::uint8_t {False, True, Fail};
 
     Result isUsedAsBool(const char code[], const char pattern[]) {
         Tokenizer tokenizer(settingsDefault, this);
diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index faa75ca6af62..00744d149668 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -5904,7 +5904,7 @@ class TestTokenizer : public TestFixture {
         ASSERT_EQUALS("a ? ( b < c ) : d > e", tokenizeAndStringify("a ? b < c : d > e"));
     }
 
-    enum class AstStyle {
+    enum class AstStyle : std::uint8_t {
         Simple,
         Z3
     };
diff --git a/tools/dmake/dmake.cpp b/tools/dmake/dmake.cpp
index 6de023f5cea4..ec2d1223a010 100644
--- a/tools/dmake/dmake.cpp
+++ b/tools/dmake/dmake.cpp
@@ -241,7 +241,7 @@ static int write_vcxproj(const std::string &proj_name, const std::function<void(
     return EXIT_SUCCESS;
 }
 
-enum ClType { Compile, Include, Precompile };
+enum ClType : std::uint8_t { Compile, Include, Precompile };
 
 static std::string make_vcxproj_cl_entry(const std::string& file, ClType type)
 {