diff --git a/libs/utils/src/CString.cpp b/libs/utils/src/CString.cpp
index d515d02457..34a998cb23 100644
--- a/libs/utils/src/CString.cpp
+++ b/libs/utils/src/CString.cpp
@@ -77,9 +77,24 @@ CString& CString::replace(size_type const pos, size_type len, char const* str, s
 
     len = std::min(len, size() - pos);
 
-    // The new size of the string, after the replacement.
     const size_type newSize = size() - len + l;
 
+    // if the new string is not longer, we can do it in-place, which is much faster.
+    if (newSize <= size()) {
+        if (mCStr) {
+            // This is equivalent to l <= len because capacity() == size()
+            // move the tail of the string. +1 to move the null-terminator
+            std::copy(mCStr + pos + len, mCStr + size() + 1, mCStr + pos + l);
+            // copy the new content
+            std::copy_n(str, l, mCStr + pos);
+            // update the size
+            (mData - 1)->length = newSize;
+        }
+        // if mCStr is null, newSize<=size() implies l<=len and since size is 0, len is 0, so l is 0.
+        // so we're replacing nothing with nothing and there is nothing to do.
+        return *this;
+    }
+
     // Allocate enough memory to hold the new string.
     Data* const p = static_cast<Data*>(std::malloc(sizeof(Data) + newSize + 1));
     assert(p);
diff --git a/libs/utils/test/test_CString.cpp b/libs/utils/test/test_CString.cpp
index e37861aa92..ab5d12c41a 100644
--- a/libs/utils/test/test_CString.cpp
+++ b/libs/utils/test/test_CString.cpp
@@ -477,6 +477,62 @@ TEST(CString, Replace) {
     }
 }
 
+TEST(CString, ReplaceInPlace) {
+    // Shrinking replacement
+    {
+        CString str("0123456789");
+        const char* const original_cstr = str.c_str();
+        str.replace(3, 3, "ab");
+        EXPECT_STREQ("012ab6789", str.c_str());
+        EXPECT_EQ(9, str.length());
+        EXPECT_EQ(original_cstr, str.c_str());
+    }
+    {
+        CString str("0123456789");
+        const char* const original_cstr = str.c_str();
+        str.replace(0, 3, "ab");
+        EXPECT_STREQ("ab3456789", str.c_str());
+        EXPECT_EQ(9, str.length());
+        EXPECT_EQ(original_cstr, str.c_str());
+    }
+    {
+        CString str("0123456789");
+        const char* const original_cstr = str.c_str();
+        str.replace(7, 3, "ab");
+        EXPECT_STREQ("0123456ab", str.c_str());
+        EXPECT_EQ(9, str.length());
+        EXPECT_EQ(original_cstr, str.c_str());
+    }
+    {
+        CString str("0123456789");
+        const char* const original_cstr = str.c_str();
+        str.replace(0, 10, "ab");
+        EXPECT_STREQ("ab", str.c_str());
+        EXPECT_EQ(2, str.length());
+        EXPECT_EQ(original_cstr, str.c_str());
+    }
+
+    // Same size replacement
+    {
+        CString str("0123456789");
+        const char* const original_cstr = str.c_str();
+        str.replace(0, 10, "abcdefghij");
+        EXPECT_STREQ("abcdefghij", str.c_str());
+        EXPECT_EQ(10, str.length());
+        EXPECT_EQ(original_cstr, str.c_str());
+    }
+
+    // Shrink to empty
+    {
+        CString str("0123456789");
+        const char* const original_cstr = str.c_str();
+        str.replace(3, 3, "");
+        EXPECT_STREQ("0126789", str.c_str());
+        EXPECT_EQ(7, str.length());
+        EXPECT_EQ(original_cstr, str.c_str());
+    }
+}
+
 TEST(CString, ReplaceZeroLength) {
     {
         std::string str("foobar");