diff --git a/include/exiv2/asfvideo.hpp b/include/exiv2/asfvideo.hpp
index 1b1f3fd17e..67f4619f6d 100644
--- a/include/exiv2/asfvideo.hpp
+++ b/include/exiv2/asfvideo.hpp
@@ -82,7 +82,7 @@ class EXIV2API AsfVideo : public Image {
     // Constructor to create a GUID object from a byte array
     explicit GUIDTag(const uint8_t* bytes);
 
-    std::string to_string();
+    std::string to_string() const;
 
     bool operator<(const GUIDTag& other) const;
   };
diff --git a/src/asfvideo.cpp b/src/asfvideo.cpp
index 2674cfc9ad..35f2294aa7 100644
--- a/src/asfvideo.cpp
+++ b/src/asfvideo.cpp
@@ -12,6 +12,7 @@
 #include "error.hpp"
 #include "futils.hpp"
 #include "helper_functions.hpp"
+#include "image_int.hpp"
 #include "utils.hpp"
 // *****************************************************************************
 // class member definitions
@@ -58,24 +59,12 @@ AsfVideo::GUIDTag::GUIDTag(const uint8_t* bytes) {
   }
 }
 
-std::string AsfVideo::GUIDTag::to_string() {
-  // Convert each field of the GUID structure to a string
-  std::stringstream ss;
-  ss << std::hex << std::setw(8) << std::setfill('0') << data1_ << "-";
-  ss << std::hex << std::setw(4) << std::setfill('0') << data2_ << "-";
-  ss << std::hex << std::setw(4) << std::setfill('0') << data3_ << "-";
-
-  for (size_t i = 0; i < 8; i++) {
-    if (i == 2) {
-      ss << "-";
-    }
-    ss << std::hex << std::setw(2) << std::setfill('0') << static_cast<int>(data4_[i]);
-  }
-
+std::string AsfVideo::GUIDTag::to_string() const {
   // Concatenate all strings into a single string
   // Convert the string to uppercase
   // Example of output 399595EC-8667-4E2D-8FDB-98814CE76C1E
-  return Internal::upper(ss.str());
+  return stringFormat("{:08X}-{:04X}-{:04X}-{:02X}{:02X}-{:02X}{:02X}{:02X}{:02X}{:02X}{:02X}", data1_, data2_, data3_,
+                      data4_[0], data4_[1], data4_[2], data4_[3], data4_[4], data4_[5], data4_[6], data4_[7]);
 }
 
 bool AsfVideo::GUIDTag::operator<(const GUIDTag& other) const {
diff --git a/src/basicio.cpp b/src/basicio.cpp
index 0a905078af..686ecfeca4 100644
--- a/src/basicio.cpp
+++ b/src/basicio.cpp
@@ -930,9 +930,7 @@ std::string XPathIo::writeDataToFile(const std::string& orgPath) {
 
   // generating the name for temp file.
   std::time_t timestamp = std::time(nullptr);
-  std::stringstream ss;
-  ss << timestamp << XPathIo::TEMP_FILE_EXT;
-  std::string path = ss.str();
+  auto path = stringFormat("{}{}", timestamp, XPathIo::TEMP_FILE_EXT);
 
   if (prot == pStdin) {
     if (isatty(fileno(stdin)))
@@ -1437,9 +1435,7 @@ void HttpIo::HttpImpl::getDataByRange(size_t lowBlock, size_t highBlock, std::st
   request["verb"] = "GET";
   std::string errors;
   if (lowBlock != std::numeric_limits<size_t>::max() && highBlock != std::numeric_limits<size_t>::max()) {
-    std::stringstream ss;
-    ss << "Range: bytes=" << lowBlock * blockSize_ << "-" << (((highBlock + 1) * blockSize_) - 1) << "\r\n";
-    request["header"] = ss.str();
+    request["header"] = stringFormat("Range: bytes={}-{}", lowBlock * blockSize_, (highBlock + 1) * (blockSize_ - 1));
   }
 
   int serverCode = http(request, responseDic, errors);
@@ -1480,15 +1476,10 @@ void HttpIo::HttpImpl::writeRemote(const byte* data, size_t size, size_t from, s
   // url encode
   const std::string urlencodeData = urlencode(encodeData.data());
 
-  std::stringstream ss;
-  ss << "path=" << hostInfo_.Path << "&"
-     << "from=" << from << "&"
-     << "to=" << to << "&"
-     << "data=" << urlencodeData;
-  std::string postData = ss.str();
+  auto postData = stringFormat("path={}&from={}&to={}&data={}", hostInfo_.Path, from, to, urlencodeData);
 
   // create the header
-  ss.str("");
+  std::stringstream ss;
   ss << "Content-Length: " << postData.length() << "\n"
      << "Content-Type: application/x-www-form-urlencoded\n"
      << "\n"
@@ -1616,9 +1607,7 @@ void CurlIo::CurlImpl::getDataByRange(size_t lowBlock, size_t highBlock, std::st
   // curl_easy_setopt(curl_, CURLOPT_VERBOSE, 1); // debugging mode
 
   if (lowBlock != std::numeric_limits<size_t>::max() && highBlock != std::numeric_limits<size_t>::max()) {
-    std::stringstream ss;
-    ss << lowBlock * blockSize_ << "-" << (((highBlock + 1) * blockSize_) - 1);
-    std::string range = ss.str();
+    auto range = stringFormat("{}-{}", lowBlock * blockSize_, (highBlock + 1) * (blockSize_ - 1));
     curl_easy_setopt(curl_, CURLOPT_RANGE, range.c_str());
   }
 
@@ -1662,12 +1651,7 @@ void CurlIo::CurlImpl::writeRemote(const byte* data, size_t size, size_t from, s
   base64encode(data, size, encodeData.data(), encodeLength);
   // url encode
   const std::string urlencodeData = urlencode(encodeData.data());
-  std::stringstream ss;
-  ss << "path=" << hostInfo.Path << "&"
-     << "from=" << from << "&"
-     << "to=" << to << "&"
-     << "data=" << urlencodeData;
-  std::string postData = ss.str();
+  auto postData = stringFormat("path={}&from={}&to={}&data={}", hostInfo.Path, from, to, urlencodeData);
 
   curl_easy_setopt(curl_, CURLOPT_POSTFIELDS, postData.c_str());
   // Perform the request, res will get the return code.