diff --git a/components/headless/command_handler/headless_command_handler.cc b/components/headless/command_handler/headless_command_handler.cc
index 140f86ae20c2b2..a15b468d9040e0 100644
--- a/components/headless/command_handler/headless_command_handler.cc
+++ b/components/headless/command_handler/headless_command_handler.cc
@@ -2,11 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifdef UNSAFE_BUFFERS_BUILD
-// TODO(crbug.com/40285824): Remove this and convert code to safer constructs.
-#pragma allow_unsafe_buffers
-#endif
-
 #include "components/headless/command_handler/headless_command_handler.h"
 
 #include <cstdint>
@@ -265,8 +260,7 @@ bool GetCommandDictAndOutputPaths(base::Value::Dict* commands,
 }
 
 bool WriteFileTask(base::FilePath file_path, std::string file_data) {
-  auto file_span = base::make_span(
-      reinterpret_cast<const uint8_t*>(file_data.data()), file_data.size());
+  auto file_span = base::as_byte_span(file_data);
   if (!base::WriteFile(file_path, file_span)) {
     PLOG(ERROR) << "Failed to write file " << file_path;
     return false;
diff --git a/components/headless/test/capture_std_stream.cc b/components/headless/test/capture_std_stream.cc
index 976a13cc2e9d69..1ab38358c6fd54 100644
--- a/components/headless/test/capture_std_stream.cc
+++ b/components/headless/test/capture_std_stream.cc
@@ -2,11 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifdef UNSAFE_BUFFERS_BUILD
-// TODO(crbug.com/40285824): Remove this and convert code to safer constructs.
-#pragma allow_unsafe_buffers
-#endif
-
 #include "components/headless/test/capture_std_stream.h"
 
 #include <fcntl.h>
@@ -30,9 +25,9 @@ static constexpr char kPipeEnd = '\xff';
 
 CaptureStdStream::CaptureStdStream(FILE* stream) : stream_(stream) {
 #if BUILDFLAG(IS_WIN)
-  CHECK_EQ(_pipe(pipes_, 4096, O_BINARY), 0);
+  CHECK_EQ(_pipe(pipes_.data(), 4096, O_BINARY), 0);
 #else
-  CHECK_EQ(pipe(pipes_), 0);
+  CHECK_EQ(pipe(pipes_.data()), 0);
 #endif
   fileno_ = dup(fileno(stream_));
   CHECK_NE(fileno_, -1);
@@ -76,13 +71,15 @@ std::string CaptureStdStream::TakeCapturedData() {
   std::string captured_data;
   for (;;) {
     constexpr size_t kChunkSize = 256;
-    char buffer[kChunkSize];
-    int bytes_read = read(pipes_[kReadPipe], buffer, kChunkSize);
+    std::array<char, kChunkSize> buffer;
+    int bytes_read = read(pipes_[kReadPipe], buffer.data(), kChunkSize);
     CHECK_GT(bytes_read, 0);
-    if (buffer[bytes_read - 1] != kPipeEnd) {
-      captured_data.append(buffer, bytes_read);
+    std::string_view data(buffer.data(), bytes_read);
+    if (data.back() != kPipeEnd) {
+      captured_data.append(data);
     } else {
-      captured_data.append(buffer, bytes_read - 1);
+      data.remove_suffix(1);
+      captured_data.append(data);
       break;
     }
   }
diff --git a/components/headless/test/capture_std_stream.h b/components/headless/test/capture_std_stream.h
index c69b150e043dd9..27b43c30a478fb 100644
--- a/components/headless/test/capture_std_stream.h
+++ b/components/headless/test/capture_std_stream.h
@@ -28,7 +28,7 @@ class CaptureStdStream {
   raw_ptr<FILE> stream_;
 
   int fileno_ = -1;
-  int pipes_[2] = {-1, -1};
+  std::array<int, 2> pipes_ = {-1, -1};
   bool capturing_ = false;
 
   // TODO(https://github.com/llvm/llvm-project/issues/61334): Explicit
diff --git a/headless/test/headless_printtopdf_browsertest.cc b/headless/test/headless_printtopdf_browsertest.cc
index 69fef0f7b9c70e..874961b6370c77 100644
--- a/headless/test/headless_printtopdf_browsertest.cc
+++ b/headless/test/headless_printtopdf_browsertest.cc
@@ -2,11 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifdef UNSAFE_BUFFERS_BUILD
-// TODO(crbug.com/351564777): Remove this and convert code to safer constructs.
-#pragma allow_unsafe_buffers
-#endif
-
 #include <memory>
 #include <optional>
 #include <string>
@@ -85,9 +80,7 @@ class HeadlessPDFPagesBrowserTest : public HeadlessDevTooledBrowserTest {
     ASSERT_TRUE(base::Base64Decode(pdf_data_base64, &pdf_data));
     EXPECT_GT(pdf_data.size(), 0U);
 
-    auto pdf_span = base::make_span(
-        reinterpret_cast<const uint8_t*>(pdf_data.data()), pdf_data.size());
-
+    auto pdf_span = base::as_byte_span(pdf_data);
     int num_pages;
     EXPECT_TRUE(chrome_pdf::GetPDFDocInfo(pdf_span, &num_pages, nullptr));
     EXPECT_EQ(std::ceil(kDocHeight / kPaperHeight), num_pages);
@@ -195,8 +188,7 @@ class HeadlessPDFStreamBrowserTest : public HeadlessDevTooledBrowserTest {
     ASSERT_TRUE(base::Base64Decode(base64_pdf_data_, &pdf_data));
     EXPECT_GT(pdf_data.size(), 0U);
 
-    auto pdf_span = base::make_span(
-        reinterpret_cast<const uint8_t*>(pdf_data.data()), pdf_data.size());
+    auto pdf_span = base::as_byte_span(pdf_data);
 
     int num_pages;
     EXPECT_TRUE(chrome_pdf::GetPDFDocInfo(pdf_span, &num_pages, nullptr));
@@ -254,8 +246,7 @@ class HeadlessPDFBrowserTestBase : public HeadlessDevTooledBrowserTest {
       ASSERT_TRUE(base::Base64Decode(pdf_data_base64, &pdf_data));
       ASSERT_GT(pdf_data.size(), 0U);
 
-      auto pdf_span = base::make_span(
-          reinterpret_cast<const uint8_t*>(pdf_data.data()), pdf_data.size());
+      auto pdf_span = base::as_byte_span(pdf_data);
       int num_pages;
       ASSERT_TRUE(chrome_pdf::GetPDFDocInfo(pdf_span, &num_pages, nullptr));
       OnPDFReady(pdf_span, num_pages);