diff --git a/cpr/cookies.cpp b/cpr/cookies.cpp
index 9d351fd78..41e12469a 100644
--- a/cpr/cookies.cpp
+++ b/cpr/cookies.cpp
@@ -26,7 +26,7 @@ const std::chrono::system_clock::time_point Cookie::GetExpires() const {
 const std::string Cookie::GetExpiresString() const {
     std::stringstream ss;
     std::tm tm{};
-    std::time_t tt = std::chrono::system_clock::to_time_t(expires_);
+    const std::time_t tt = std::chrono::system_clock::to_time_t(expires_);
 #ifdef _WIN32
     gmtime_s(&tm, &tt);
 #else
diff --git a/cpr/curl_container.cpp b/cpr/curl_container.cpp
index d40f90f5d..c90b777a3 100644
--- a/cpr/curl_container.cpp
+++ b/cpr/curl_container.cpp
@@ -25,11 +25,11 @@ const std::string CurlContainer<Parameter>::GetContent(const CurlHolder& holder)
             content += "&";
         }
 
-        std::string escapedKey = encode ? holder.urlEncode(parameter.key) : parameter.key;
+        const std::string escapedKey = encode ? holder.urlEncode(parameter.key) : parameter.key;
         if (parameter.value.empty()) {
             content += escapedKey;
         } else {
-            std::string escapedValue = encode ? holder.urlEncode(parameter.value) : parameter.value;
+            const std::string escapedValue = encode ? holder.urlEncode(parameter.value) : parameter.value;
             content += escapedKey + "=";
             content += escapedValue;
         }
@@ -45,7 +45,7 @@ const std::string CurlContainer<Pair>::GetContent(const CurlHolder& holder) cons
         if (!content.empty()) {
             content += "&";
         }
-        std::string escaped = encode ? holder.urlEncode(element.value) : element.value;
+        const std::string escaped = encode ? holder.urlEncode(element.value) : element.value;
         content += element.key + "=" + escaped;
     }
 
diff --git a/cpr/redirect.cpp b/cpr/redirect.cpp
index fade13045..f95dc7567 100644
--- a/cpr/redirect.cpp
+++ b/cpr/redirect.cpp
@@ -19,7 +19,7 @@ PostRedirectFlags operator~(PostRedirectFlags flag) {
 
 PostRedirectFlags& operator|=(PostRedirectFlags& lhs, PostRedirectFlags rhs) {
     lhs = static_cast<PostRedirectFlags>(static_cast<uint8_t>(lhs) | static_cast<uint8_t>(rhs));
-    uint8_t tmp = static_cast<uint8_t>(lhs);
+    const uint8_t tmp = static_cast<uint8_t>(lhs);
     lhs = static_cast<PostRedirectFlags>(tmp);
     return lhs;
 }
diff --git a/cpr/session.cpp b/cpr/session.cpp
index eb135a96e..dace5334a 100644
--- a/cpr/session.cpp
+++ b/cpr/session.cpp
@@ -71,7 +71,7 @@ void Session::SetBearer(const Bearer& token) {
 Session::Session() : curl_(new CurlHolder()) {
     // Set up some sensible defaults
     curl_version_info_data* version_info = curl_version_info(CURLVERSION_NOW);
-    std::string version = "curl/" + std::string{version_info->version};
+    const std::string version = "curl/" + std::string{version_info->version};
     curl_easy_setopt(curl_->handle, CURLOPT_USERAGENT, version.c_str());
     SetRedirect(Redirect());
     curl_easy_setopt(curl_->handle, CURLOPT_NOPROGRESS, 1L);
@@ -90,7 +90,7 @@ Response Session::makeDownloadRequest() {
     assert(curl_->handle);
 
     if (!interceptors_.empty()) {
-        std::shared_ptr<Interceptor> interceptor = interceptors_.front();
+        const std::shared_ptr<Interceptor> interceptor = interceptors_.front();
         interceptors_.pop();
         return interceptor->intercept(*this);
     }
@@ -100,13 +100,13 @@ Response Session::makeDownloadRequest() {
 
     const std::string parametersContent = parameters_.GetContent(*curl_);
     if (!parametersContent.empty()) {
-        Url new_url{url_ + "?" + parametersContent};
+        const Url new_url{url_ + "?" + parametersContent};
         curl_easy_setopt(curl_->handle, CURLOPT_URL, new_url.c_str());
     } else {
         curl_easy_setopt(curl_->handle, CURLOPT_URL, url_.c_str());
     }
 
-    std::string protocol = url_.str().substr(0, url_.str().find(':'));
+    const std::string protocol = url_.str().substr(0, url_.str().find(':'));
     if (proxies_.has(protocol)) {
         curl_easy_setopt(curl_->handle, CURLOPT_PROXY, proxies_[protocol].c_str());
         if (proxyAuth_.has(protocol)) {
@@ -126,7 +126,7 @@ Response Session::makeDownloadRequest() {
         curl_easy_setopt(curl_->handle, CURLOPT_HEADERDATA, &header_string);
     }
 
-    CURLcode curl_error = curl_easy_perform(curl_->handle);
+    const CURLcode curl_error = curl_easy_perform(curl_->handle);
 
     if (!headercb_.callback) {
         curl_easy_setopt(curl_->handle, CURLOPT_HEADERFUNCTION, nullptr);
@@ -150,14 +150,14 @@ void Session::prepareCommon() {
 
     const std::string parametersContent = parameters_.GetContent(*curl_);
     if (!parametersContent.empty()) {
-        Url new_url{url_ + "?" + parametersContent};
+        const Url new_url{url_ + "?" + parametersContent};
         curl_easy_setopt(curl_->handle, CURLOPT_URL, new_url.c_str());
     } else {
         curl_easy_setopt(curl_->handle, CURLOPT_URL, url_.c_str());
     }
 
     // Proxy:
-    std::string protocol = url_.str().substr(0, url_.str().find(':'));
+    const std::string protocol = url_.str().substr(0, url_.str().find(':'));
     if (proxies_.has(protocol)) {
         curl_easy_setopt(curl_->handle, CURLOPT_PROXY, proxies_[protocol].c_str());
         if (proxyAuth_.has(protocol)) {
@@ -217,12 +217,12 @@ void Session::prepareCommon() {
 Response Session::makeRequest() {
     if (!interceptors_.empty()) {
         // At least one interceptor exists -> Execute its intercept function
-        std::shared_ptr<Interceptor> interceptor = interceptors_.front();
+        const std::shared_ptr<Interceptor> interceptor = interceptors_.front();
         interceptors_.pop();
         return interceptor->intercept(*this);
     }
 
-    CURLcode curl_error = curl_easy_perform(curl_->handle);
+    const CURLcode curl_error = curl_easy_perform(curl_->handle);
     return Complete(curl_error);
 }
 
@@ -602,12 +602,12 @@ void Session::SetHttpVersion(const HttpVersion& version) {
 }
 
 void Session::SetRange(const Range& range) {
-    std::string range_str = range.str();
+    const std::string range_str = range.str();
     curl_easy_setopt(curl_->handle, CURLOPT_RANGE, range_str.c_str());
 }
 
 void Session::SetMultiRange(const MultiRange& multi_range) {
-    std::string multi_range_str = multi_range.str();
+    const std::string multi_range_str = multi_range.str();
     curl_easy_setopt(curl_->handle, CURLOPT_RANGE, multi_range_str.c_str());
 }
 
@@ -627,7 +627,7 @@ cpr_off_t Session::GetDownloadFileLength() {
     cpr_off_t downloadFileLenth = -1;
     curl_easy_setopt(curl_->handle, CURLOPT_URL, url_.c_str());
 
-    std::string protocol = url_.str().substr(0, url_.str().find(':'));
+    const std::string protocol = url_.str().substr(0, url_.str().find(':'));
     if (proxies_.has(protocol)) {
         curl_easy_setopt(curl_->handle, CURLOPT_PROXY, proxies_[protocol].c_str());
         if (proxyAuth_.has(protocol)) {
diff --git a/cpr/ssl_ctx.cpp b/cpr/ssl_ctx.cpp
index ceeaa3d1d..a8d14eb84 100644
--- a/cpr/ssl_ctx.cpp
+++ b/cpr/ssl_ctx.cpp
@@ -47,7 +47,7 @@ CURLcode sslctx_function_load_ca_cert_from_buffer(CURL* /*curl*/, void* sslctx,
     store = SSL_CTX_get_cert_store(static_cast<SSL_CTX*>(sslctx));
 
     // Add the loaded certificate to the verification storage
-    int status = X509_STORE_add_cert(store, cert);
+    const int status = X509_STORE_add_cert(store, cert);
     if (status == 0) {
         printf("Error adding certificate\n");
         return CURLE_ABORTED_BY_CALLBACK;
diff --git a/cpr/threadpool.cpp b/cpr/threadpool.cpp
index 1d65acad0..8ab1ee820 100644
--- a/cpr/threadpool.cpp
+++ b/cpr/threadpool.cpp
@@ -124,7 +124,7 @@ void ThreadPool::AddThread(std::thread* thread) {
 }
 
 void ThreadPool::DelThread(std::thread::id id) {
-    time_t now = time(nullptr);
+    const time_t now = time(nullptr);
     thread_mutex.lock();
     --cur_thread_num;
     --idle_thread_num;
diff --git a/cpr/util.cpp b/cpr/util.cpp
index 0a0d9eff2..5b9b75709 100644
--- a/cpr/util.cpp
+++ b/cpr/util.cpp
@@ -52,7 +52,7 @@ Cookies parseCookies(curl_slist* raw_cookies) {
         while (tokens.size() < CURL_HTTP_COOKIE_SIZE) {
             tokens.emplace_back("");
         }
-        std::time_t expires = static_cast<time_t>(std::stoul(tokens.at(static_cast<size_t>(CurlHTTPCookieField::Expires))));
+        const std::time_t expires = static_cast<time_t>(std::stoul(tokens.at(static_cast<size_t>(CurlHTTPCookieField::Expires))));
         cookies.emplace_back(Cookie{
                 tokens.at(static_cast<size_t>(CurlHTTPCookieField::Name)),
                 tokens.at(static_cast<size_t>(CurlHTTPCookieField::Value)),
@@ -88,7 +88,7 @@ Header parseHeader(const std::string& headers, std::string* status_line, std::st
 
                 // set the reason if it was given
                 if (reason != nullptr) {
-                    size_t pos1 = line.find_first_of("\t ");
+                    const size_t pos1 = line.find_first_of("\t ");
                     size_t pos2 = std::string::npos;
                     if (pos1 != std::string::npos) {
                         pos2 = line.find_first_of("\t ", pos1 + 1);
@@ -103,7 +103,7 @@ Header parseHeader(const std::string& headers, std::string* status_line, std::st
         }
 
         if (line.length() > 0) {
-            size_t found = line.find(':');
+            const size_t found = line.find(':');
             if (found != std::string::npos) {
                 std::string value = line.substr(found + 1);
                 value.erase(0, value.find_first_not_of("\t "));
@@ -179,7 +179,7 @@ int debugUserFunction(CURL* /*handle*/, curl_infotype type, char* data, size_t s
  * std::string result = holder.urlEncode(input);
  **/
 std::string urlEncode(const std::string& s) {
-    CurlHolder holder; // Create a temporary new holder for URL encoding
+    const CurlHolder holder; // Create a temporary new holder for URL encoding
     return holder.urlEncode(s);
 }
 
@@ -194,7 +194,7 @@ std::string urlEncode(const std::string& s) {
  * std::string result = holder.urlDecode(input);
  **/
 std::string urlDecode(const std::string& s) {
-    CurlHolder holder; // Create a temporary new holder for URL decoding
+    const CurlHolder holder; // Create a temporary new holder for URL decoding
     return holder.urlDecode(s);
 }