diff --git a/include/nlohmann/detail/input/binary_reader.hpp b/include/nlohmann/detail/input/binary_reader.hpp
index e4e1f1760..a45d9983a 100644
--- a/include/nlohmann/detail/input/binary_reader.hpp
+++ b/include/nlohmann/detail/input/binary_reader.hpp
@@ -6,12 +6,10 @@
 #include <cmath> // ldexp
 #include <cstddef> // size_t
 #include <cstdint> // uint8_t, uint16_t, uint32_t, uint64_t
+#include <cstdio> // snprinft
 #include <cstring> // memcpy
-#include <iomanip> // setw, setfill
-#include <ios> // hex
 #include <iterator> // back_inserter
 #include <limits> // numeric_limits
-#include <sstream> // stringstream
 #include <string> // char_traits, string
 #include <utility> // make_pair, move
 
@@ -1665,9 +1663,9 @@ class binary_reader
     */
     std::string get_token_string() const
     {
-        std::stringstream ss;
-        ss << std::setw(2) << std::uppercase << std::setfill('0') << std::hex << current;
-        return ss.str();
+        char cr[3];
+        snprintf(cr, 3, "%.2X", current);
+        return std::string{cr};
     }
 
   private:
diff --git a/include/nlohmann/detail/input/lexer.hpp b/include/nlohmann/detail/input/lexer.hpp
index 7b31068f7..3fb790689 100644
--- a/include/nlohmann/detail/input/lexer.hpp
+++ b/include/nlohmann/detail/input/lexer.hpp
@@ -3,10 +3,8 @@
 #include <clocale> // localeconv
 #include <cstddef> // size_t
 #include <cstdlib> // strtof, strtod, strtold, strtoll, strtoull
+#include <cstdio> // snprintf
 #include <initializer_list> // initializer_list
-#include <ios> // hex, uppercase
-#include <iomanip> // setw, setfill
-#include <sstream> // stringstream
 #include <string> // char_traits, string
 #include <vector> // vector
 
@@ -1174,10 +1172,9 @@ scan_number_done:
             if ('\x00' <= c and c <= '\x1F')
             {
                 // escape control characters
-                std::stringstream ss;
-                ss << "<U+" << std::setw(4) << std::uppercase << std::setfill('0')
-                   << std::hex << static_cast<int>(c) << ">";
-                result += ss.str();
+                char cs[9];
+                snprintf(cs, 9, "<U+%.4X>", c);
+                result += cs;
             }
             else
             {
diff --git a/include/nlohmann/detail/output/serializer.hpp b/include/nlohmann/detail/output/serializer.hpp
index a64426444..f6fa152aa 100644
--- a/include/nlohmann/detail/output/serializer.hpp
+++ b/include/nlohmann/detail/output/serializer.hpp
@@ -9,11 +9,8 @@
 #include <cstddef> // size_t, ptrdiff_t
 #include <cstdint> // uint8_t
 #include <cstdio> // snprintf
-#include <iomanip> // setfill
-#include <iterator> // next
 #include <limits> // numeric_limits
 #include <string> // string
-#include <sstream> // stringstream
 #include <type_traits> // is_same
 
 #include <nlohmann/detail/exceptions.hpp>
@@ -389,9 +386,9 @@ class serializer
 
                 case UTF8_REJECT:  // decode found invalid UTF-8 byte
                 {
-                    std::stringstream ss;
-                    ss << std::setw(2) << std::uppercase << std::setfill('0') << std::hex << static_cast<int>(byte);
-                    JSON_THROW(type_error::create(316, "invalid UTF-8 byte at index " + std::to_string(i) + ": 0x" + ss.str()));
+                    std::string sn(3, '\0');
+                    snprintf(&sn[0], sn.size(), "%.2X", byte);
+                    JSON_THROW(type_error::create(316, "invalid UTF-8 byte at index " + std::to_string(i) + ": 0x" + sn));
                 }
 
                 default:  // decode found yet incomplete multi-byte code point
@@ -417,9 +414,9 @@ class serializer
         else
         {
             // we finish reading, but do not accept: string was incomplete
-            std::stringstream ss;
-            ss << std::setw(2) << std::uppercase << std::setfill('0') << std::hex << static_cast<int>(static_cast<uint8_t>(s.back()));
-            JSON_THROW(type_error::create(316, "incomplete UTF-8 string; last byte: 0x" + ss.str()));
+            std::string sn(3,'\0');
+            snprintf(&sn[0], sn.size(), "%.2X", s.back());
+            JSON_THROW(type_error::create(316, "incomplete UTF-8 string; last byte: 0x" + sn));
         }
     }