diff --git a/core/fpdfapi/edit/cpdf_creator.cpp b/core/fpdfapi/edit/cpdf_creator.cpp
index 9a97a80..87ca911 100644
--- a/core/fpdfapi/edit/cpdf_creator.cpp
+++ b/core/fpdfapi/edit/cpdf_creator.cpp
@@ -24,6 +24,7 @@
 #include "core/fxcrt/fx_memory_wrappers.h"
 #include "core/fxcrt/fx_random.h"
 #include "core/fxcrt/fx_safe_types.h"
+#include "core/fxcrt/span_util.h"
 #include "core/fxcrt/stl_util.h"
 #include "third_party/base/check.h"
 #include "third_party/base/containers/contains.h"
@@ -82,7 +83,8 @@
   size_t temp_size = size;
   while (temp_size) {
     size_t buf_size = std::min(kArchiveBufferSize - current_length_, temp_size);
-    memcpy(buffer_.data() + current_length_, buffer, buf_size);
+    fxcrt::spancpy(fxcrt::Subspan(buffer_, current_length_),
+                   pdfium::make_span(buffer, buf_size));
 
     current_length_ += buf_size;
     if (current_length_ == kArchiveBufferSize && !Flush())
diff --git a/core/fpdfapi/page/cpdf_contentparser.cpp b/core/fpdfapi/page/cpdf_contentparser.cpp
index 823a0fc..912a6ef 100644
--- a/core/fpdfapi/page/cpdf_contentparser.cpp
+++ b/core/fpdfapi/page/cpdf_contentparser.cpp
@@ -19,6 +19,7 @@
 #include "core/fpdfapi/parser/cpdf_stream_acc.h"
 #include "core/fxcrt/fx_safe_types.h"
 #include "core/fxcrt/pauseindicator_iface.h"
+#include "core/fxcrt/span_util.h"
 #include "core/fxge/cfx_fillrenderoptions.h"
 #include "third_party/base/check.h"
 #include "third_party/base/check_op.h"
@@ -173,13 +174,13 @@
     return Stage::kComplete;
 
   uint32_t pos = 0;
+  auto data_span = pdfium::make_span(m_pData.Get(), m_Size);
   for (const auto& stream : m_StreamArray) {
-    memcpy(m_pData.Get() + pos, stream->GetData(), stream->GetSize());
+    fxcrt::spancpy(data_span.subspan(pos), stream->GetSpan());
     pos += stream->GetSize();
-    m_pData.Get()[pos++] = ' ';
+    data_span[pos++] = ' ';
   }
   m_StreamArray.clear();
-
   return Stage::kParse;
 }
 
diff --git a/core/fpdfapi/page/cpdf_image.cpp b/core/fpdfapi/page/cpdf_image.cpp
index 5f32a8b..3a4ef25 100644
--- a/core/fpdfapi/page/cpdf_image.cpp
+++ b/core/fpdfapi/page/cpdf_image.cpp
@@ -26,6 +26,7 @@
 #include "core/fxcodec/jpeg/jpegmodule.h"
 #include "core/fxcrt/fx_memory_wrappers.h"
 #include "core/fxcrt/fx_stream.h"
+#include "core/fxcrt/span_util.h"
 #include "core/fxge/dib/cfx_dibitmap.h"
 #include "core/fxge/dib/fx_dib.h"
 #include "third_party/base/check.h"
@@ -290,7 +291,8 @@
   size_t dest_span_offset = 0;
   if (bCopyWithoutAlpha) {
     for (int32_t i = 0; i < BitmapHeight; i++) {
-      memcpy(&dest_span[dest_span_offset], src_buf, dest_pitch);
+      fxcrt::spancpy(dest_span.subspan(dest_span_offset),
+                     pdfium::make_span(src_buf, dest_pitch));
       dest_span_offset += dest_pitch;
       src_buf += src_pitch;
     }
diff --git a/core/fpdfapi/page/cpdf_streamparser.cpp b/core/fpdfapi/page/cpdf_streamparser.cpp
index b896cb8..da16168 100644
--- a/core/fpdfapi/page/cpdf_streamparser.cpp
+++ b/core/fpdfapi/page/cpdf_streamparser.cpp
@@ -29,6 +29,7 @@
 #include "core/fxcrt/fx_extension.h"
 #include "core/fxcrt/fx_memory_wrappers.h"
 #include "core/fxcrt/fx_safe_types.h"
+#include "core/fxcrt/span_util.h"
 #include "third_party/base/check.h"
 
 namespace {
@@ -168,8 +169,8 @@
   if (decoder.IsEmpty()) {
     dwOrigSize = std::min<uint32_t>(dwOrigSize, m_pBuf.size() - m_Pos);
     pData.reset(FX_AllocUninit(uint8_t, dwOrigSize));
-    auto copy_span = m_pBuf.subspan(m_Pos, dwOrigSize);
-    memcpy(pData.get(), copy_span.data(), copy_span.size());
+    auto dest_span = pdfium::make_span(pData.get(), dwOrigSize);
+    fxcrt::spancpy(dest_span, m_pBuf.subspan(m_Pos, dwOrigSize));
     dwStreamSize = dwOrigSize;
     m_Pos += dwOrigSize;
   } else {
@@ -198,8 +199,8 @@
     }
     m_Pos = dwSavePos;
     pData.reset(FX_AllocUninit(uint8_t, dwStreamSize));
-    auto copy_span = m_pBuf.subspan(m_Pos, dwStreamSize);
-    memcpy(pData.get(), copy_span.data(), copy_span.size());
+    auto dest_span = pdfium::make_span(pData.get(), dwStreamSize);
+    fxcrt::spancpy(dest_span, m_pBuf.subspan(m_Pos, dwStreamSize));
     m_Pos += dwStreamSize;
   }
   pDict->SetNewFor<CPDF_Number>("Length", static_cast<int>(dwStreamSize));
diff --git a/core/fpdfapi/parser/cpdf_seekablemultistream.cpp b/core/fpdfapi/parser/cpdf_seekablemultistream.cpp
index 578db3e..449b2cc 100644
--- a/core/fpdfapi/parser/cpdf_seekablemultistream.cpp
+++ b/core/fpdfapi/parser/cpdf_seekablemultistream.cpp
@@ -9,6 +9,7 @@
 #include <algorithm>
 
 #include "core/fpdfapi/parser/cpdf_stream_acc.h"
+#include "core/fxcrt/span_util.h"
 #include "core/fxcrt/stl_util.h"
 #include "third_party/base/notreached.h"
 
@@ -43,16 +44,16 @@
     offset -= dwSize;
     index++;
   }
+  auto buffer_span = pdfium::make_span(static_cast<uint8_t*>(buffer), size);
   while (index < iCount) {
-    const auto& acc = m_Data[index];
-    uint32_t dwSize = acc->GetSize();
-    size_t dwRead = std::min(size, static_cast<size_t>(dwSize - offset));
-    memcpy(buffer, acc->GetSpan().subspan(offset, dwRead).data(), dwRead);
-    size -= dwRead;
-    if (size == 0)
+    auto acc_span = m_Data[index]->GetSpan();
+    size_t dwRead =
+        std::min<size_t>(buffer_span.size(), acc_span.size() - offset);
+    fxcrt::spancpy(buffer_span, acc_span.subspan(offset, dwRead));
+    buffer_span = buffer_span.subspan(dwRead);
+    if (buffer_span.empty())
       return true;
 
-    buffer = static_cast<uint8_t*>(buffer) + dwRead;
     offset = 0;
     index++;
   }