diff --git a/.clang-tidy b/.clang-tidy
index a1a36f5f..c27ef5a2 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -1,6 +1,6 @@
 #Checks: '*,-clang-analyzer-alpha.*'
 #Checks: '-*,google-readability-casting,llvm-namespace-comment,performance-unnecessary-value-param,llvm-include-order,misc-throw-by-value-catch-by-reference,readability-container-size-empty,google-runtime-references,modernize*'
-Checks: '-*,llvm-namespace-comment,llvm-include-order'
+Checks: '-*,llvm-namespace-comment,llvm-include-order,readability-container-size-empty'
 HeaderFilterRegex: '.*hpp'
 CheckOptions:
 - key:             readability-braces-around-statements.ShortStatementLines
diff --git a/include/CLI/App.hpp b/include/CLI/App.hpp
index cc00f4dd..2f93e623 100644
--- a/include/CLI/App.hpp
+++ b/include/CLI/App.hpp
@@ -602,7 +602,7 @@ public:
         for(const Option_p &opt : options_) {
 
             // Only process option with a long-name
-            if(opt->lnames_.size() > 0) {
+            if(!opt->lnames_.empty()) {
                 std::string name = prefix + opt->lnames_[0];
 
                 // Non-flags
@@ -644,7 +644,7 @@ public:
             prev += " " + name_;
 
         auto selected_subcommands = get_subcommands();
-        if(selected_subcommands.size() > 0)
+        if(!selected_subcommands.empty())
             return selected_subcommands.at(0)->help(wid, prev);
 
         std::stringstream out;
@@ -676,7 +676,7 @@ public:
                     pos=true;
             }
 
-        if(subcommands_.size() > 0) {
+        if(!subcommands_.empty()) {
             if(require_subcommand_ != 0)
                 out << " SUBCOMMAND";
             else
@@ -715,7 +715,7 @@ public:
         }
 
         // Subcommands
-        if(subcommands_.size()> 0) {
+        if(!subcommands_.empty()) {
             out << "Subcommands:" << std::endl;
             for(const App_p &com : subcommands_)
                 detail::format_help(out, com->get_name(), com->description_, wid);
@@ -829,7 +829,7 @@ protected:
         parsed_ = true;
         bool positional_only = false;
         
-        while(args.size()>0) {
+        while(!args.empty()) {
             _parse_single(args, positional_only);
         }
 
@@ -842,7 +842,7 @@ protected:
         if (config_ptr_ != nullptr && config_name_ != "") {
             try {
                 std::vector<detail::ini_ret_t> values = detail::parse_ini(config_name_);
-                while(values.size() > 0) {
+                while(!values.empty()) {
                     if(!_parse_ini(values)) {
                         throw ExtrasINIError(values.back().fullname);
                     }
@@ -888,7 +888,7 @@ protected:
         }
 
         auto selected_subcommands =get_subcommands();
-        if(require_subcommand_ < 0 && selected_subcommands.size() == 0)
+        if(require_subcommand_ < 0 && selected_subcommands.empty())
             throw RequiredError("Subcommand required");
         else if(require_subcommand_ > 0 && static_cast<int>( selected_subcommands.size()) != require_subcommand_)
             throw RequiredError(std::to_string(require_subcommand_) + " subcommand(s) required");
@@ -1081,11 +1081,11 @@ protected:
 
 
         if(num == -1) {
-            while(args.size()>0 && _recognize(args.back()) == detail::Classifer::NONE) {
+            while(!args.empty() && _recognize(args.back()) == detail::Classifer::NONE) {
                 op->add_result(args.back());
                 args.pop_back();
             }
-        } else while(num>0 && args.size() > 0) {
+        } else while(num>0 && !args.empty()) {
             num--;
             std::string current_ = args.back();
             args.pop_back();
@@ -1137,11 +1137,11 @@ protected:
         }
 
         if(num == -1) {
-            while(args.size() > 0 && _recognize(args.back()) == detail::Classifer::NONE) {
+            while(!args.empty() && _recognize(args.back()) == detail::Classifer::NONE) {
                 op->add_result(args.back());
                 args.pop_back();
             }
-        } else while(num>0 && args.size()>0) {
+        } else while(num>0 && !args.empty()) {
             num--;
             op->add_result(args.back());
             args.pop_back();
diff --git a/include/CLI/Option.hpp b/include/CLI/Option.hpp
index 0f4c2421..2f42e197 100644
--- a/include/CLI/Option.hpp
+++ b/include/CLI/Option.hpp
@@ -354,12 +354,12 @@ public:
         }
         if(envname_ != "")
             out << " (env:" << envname_ << ")";
-        if(requires_.size() > 0) {
+        if(!requires_.empty()) {
             out << " Requires:";
             for(const Option* opt : requires_)
                 out << " " << opt->get_name();
         }
-        if(excludes_.size() > 0) {
+        if(!excludes_.empty()) {
             out << " Excludes:";
             for(const Option* opt : excludes_)
                 out << " " << opt->get_name();
@@ -377,7 +377,7 @@ public:
     void run_callback() const {
         if(!callback_(results_))
             throw ConversionError(get_name() + "=" + detail::join(results_));
-        if(validators_.size()>0) {
+        if(!validators_.empty()) {
             for(const std::string & result : results_)
                 for(const std::function<bool(std::string)> &vali : validators_)
                     if(!vali(result))
@@ -486,7 +486,7 @@ public:
     ///@{
     /// Can print positional name detailed option if true
     bool _has_help_positional() const {
-        return get_positional() && (has_description() || requires_.size()>0 || excludes_.size()>0 );
+        return get_positional() && (has_description() || !requires_.empty() || !excludes_.empty() );
     }
     ///@}
 };
diff --git a/include/CLI/StringTools.hpp b/include/CLI/StringTools.hpp
index 8d4534a6..f8a4ce3b 100644
--- a/include/CLI/StringTools.hpp
+++ b/include/CLI/StringTools.hpp
@@ -136,7 +136,7 @@ bool valid_later_char(T c) {
 
 /// Verify an option name
 inline bool valid_name_string(const std::string &str) {
-    if(str.size()<1 || !valid_first_char(str[0]))
+    if(str.empty() || !valid_first_char(str[0]))
         return false;
     for(auto c : str.substr(1))
         if(!valid_later_char(c))
@@ -160,7 +160,7 @@ inline std::vector<std::string> split_up(std::string str) {
 
     std::vector<std::string> output;
 
-    while(str.size() > 0) {
+    while(!str.empty()) {
         if(str[0] == '\'') {
             auto end = str.find('\'', 1);
             if(end != std::string::npos) {