diff --git a/apriltag/src/main/native/cpp/AprilTagFieldLayout.cpp b/apriltag/src/main/native/cpp/AprilTagFieldLayout.cpp
index 31e4cacb83..c14df6353c 100644
--- a/apriltag/src/main/native/cpp/AprilTagFieldLayout.cpp
+++ b/apriltag/src/main/native/cpp/AprilTagFieldLayout.cpp
@@ -8,22 +8,21 @@
 
 #include <units/angle.h>
 #include <units/length.h>
+#include <wpi/MemoryBuffer.h>
 #include <wpi/json.h>
-#include <wpi/raw_istream.h>
 #include <wpi/raw_ostream.h>
 
 using namespace frc;
 
 AprilTagFieldLayout::AprilTagFieldLayout(std::string_view path) {
-  std::error_code error_code;
-
-  wpi::raw_fd_istream input{path, error_code};
-  if (error_code) {
+  std::error_code ec;
+  std::unique_ptr<wpi::MemoryBuffer> fileBuffer =
+      wpi::MemoryBuffer::GetFile(path, ec);
+  if (fileBuffer == nullptr || ec) {
     throw std::runtime_error(fmt::format("Cannot open file: {}", path));
   }
 
-  wpi::json json;
-  input >> json;
+  wpi::json json = wpi::json::parse({fileBuffer->begin(), fileBuffer->end()});
 
   for (const auto& tag : json.at("tags").get<std::vector<AprilTag>>()) {
     m_apriltags[tag.ID] = tag;
diff --git a/cameraserver/multiCameraServer/src/main/native/cpp/main.cpp b/cameraserver/multiCameraServer/src/main/native/cpp/main.cpp
index 2a87baa29f..bd4ae2e77c 100644
--- a/cameraserver/multiCameraServer/src/main/native/cpp/main.cpp
+++ b/cameraserver/multiCameraServer/src/main/native/cpp/main.cpp
@@ -10,10 +10,10 @@
 
 #include <fmt/core.h>
 #include <networktables/NetworkTableInstance.h>
+#include <wpi/MemoryBuffer.h>
 #include <wpi/StringExtras.h>
 #include <wpi/fmt/raw_ostream.h>
 #include <wpi/json.h>
-#include <wpi/raw_istream.h>
 #include <wpi/raw_ostream.h>
 
 #include "cameraserver/CameraServer.h"
@@ -95,8 +95,9 @@ bool ReadCameraConfig(const wpi::json& config) {
 bool ReadConfig() {
   // open config file
   std::error_code ec;
-  wpi::raw_fd_istream is(configFile, ec);
-  if (ec) {
+  std::unique_ptr<wpi::MemoryBuffer> fileBuffer =
+      wpi::MemoryBuffer::GetFile(configFile, ec);
+  if (fileBuffer == nullptr || ec) {
     fmt::print(stderr, "could not open '{}': {}\n", configFile, ec.message());
     return false;
   }
@@ -104,7 +105,7 @@ bool ReadConfig() {
   // parse file
   wpi::json j;
   try {
-    j = wpi::json::parse(is);
+    j = wpi::json::parse({fileBuffer->begin(), fileBuffer->end()});
   } catch (const wpi::json::parse_error& e) {
     fmt::print(stderr, "config error in '{}': byte {}: {}\n", configFile,
                e.byte, e.what());
diff --git a/glass/src/lib/native/cpp/Context.cpp b/glass/src/lib/native/cpp/Context.cpp
index 036c38d172..4b9837f12b 100644
--- a/glass/src/lib/native/cpp/Context.cpp
+++ b/glass/src/lib/native/cpp/Context.cpp
@@ -12,11 +12,11 @@
 #include <imgui.h>
 #include <imgui_internal.h>
 #include <imgui_stdlib.h>
+#include <wpi/MemoryBuffer.h>
 #include <wpi/StringExtras.h>
 #include <wpi/fs.h>
 #include <wpi/json.h>
 #include <wpi/json_serializer.h>
-#include <wpi/raw_istream.h>
 #include <wpi/raw_ostream.h>
 #include <wpi/timestamp.h>
 #include <wpigui.h>
@@ -130,14 +130,17 @@ static bool JsonToWindow(const wpi::json& jfile, const char* filename) {
 
 static bool LoadWindowStorageImpl(const std::string& filename) {
   std::error_code ec;
-  wpi::raw_fd_istream is{filename, ec};
-  if (ec) {
+  std::unique_ptr<wpi::MemoryBuffer> fileBuffer =
+      wpi::MemoryBuffer::GetFile(filename, ec);
+  if (fileBuffer == nullptr || ec) {
     ImGui::LogText("error opening %s: %s", filename.c_str(),
                    ec.message().c_str());
     return false;
   } else {
     try {
-      return JsonToWindow(wpi::json::parse(is), filename.c_str());
+      return JsonToWindow(
+          wpi::json::parse({fileBuffer->begin(), fileBuffer->end()}),
+          filename.c_str());
     } catch (wpi::json::parse_error& e) {
       ImGui::LogText("Error loading %s: %s", filename.c_str(), e.what());
       return false;
@@ -148,8 +151,9 @@ static bool LoadWindowStorageImpl(const std::string& filename) {
 static bool LoadStorageRootImpl(Context* ctx, const std::string& filename,
                                 std::string_view rootName) {
   std::error_code ec;
-  wpi::raw_fd_istream is{filename, ec};
-  if (ec) {
+  std::unique_ptr<wpi::MemoryBuffer> fileBuffer =
+      wpi::MemoryBuffer::GetFile(filename, ec);
+  if (fileBuffer == nullptr || ec) {
     ImGui::LogText("error opening %s: %s", filename.c_str(),
                    ec.message().c_str());
     return false;
@@ -161,7 +165,9 @@ static bool LoadStorageRootImpl(Context* ctx, const std::string& filename,
       createdStorage = true;
     }
     try {
-      storage->FromJson(wpi::json::parse(is), filename.c_str());
+      storage->FromJson(
+          wpi::json::parse({fileBuffer->begin(), fileBuffer->end()}),
+          filename.c_str());
     } catch (wpi::json::parse_error& e) {
       ImGui::LogText("Error loading %s: %s", filename.c_str(), e.what());
       if (createdStorage) {
diff --git a/glass/src/lib/native/cpp/other/Field2D.cpp b/glass/src/lib/native/cpp/other/Field2D.cpp
index 67946da6fd..1d1cee7c1f 100644
--- a/glass/src/lib/native/cpp/other/Field2D.cpp
+++ b/glass/src/lib/native/cpp/other/Field2D.cpp
@@ -24,12 +24,12 @@
 #include <portable-file-dialogs.h>
 #include <units/angle.h>
 #include <units/length.h>
+#include <wpi/MemoryBuffer.h>
 #include <wpi/SmallString.h>
 #include <wpi/StringExtras.h>
 #include <wpi/StringMap.h>
 #include <wpi/fs.h>
 #include <wpi/json.h>
-#include <wpi/raw_istream.h>
 #include <wpigui.h>
 
 #include "glass/Context.h"
@@ -238,7 +238,7 @@ class FieldInfo {
  private:
   void Reset();
   bool LoadImageImpl(const std::string& fn);
-  bool LoadJson(wpi::raw_istream& is, std::string_view filename);
+  bool LoadJson(std::span<const char> is, std::string_view filename);
   void LoadJsonFile(std::string_view jsonfile);
 
   std::unique_ptr<pfd::open_file> m_fileOpener;
@@ -423,12 +423,11 @@ void FieldInfo::LoadImage() {
       for (auto&& field : fields::GetFields()) {
         if (field.name == m_builtin) {
           auto jsonstr = field.getJson();
-          wpi::raw_mem_istream is{jsonstr.data(), jsonstr.size()};
           auto imagedata = field.getImage();
           auto texture = gui::Texture::CreateFromImage(
               reinterpret_cast<const unsigned char*>(imagedata.data()),
               imagedata.size());
-          if (texture && LoadJson(is, {})) {
+          if (texture && LoadJson({jsonstr.data(), jsonstr.size()}, {})) {
             m_texture = std::move(texture);
             m_imageWidth = m_texture.GetWidth();
             m_imageHeight = m_texture.GetHeight();
@@ -445,11 +444,11 @@ void FieldInfo::LoadImage() {
   }
 }
 
-bool FieldInfo::LoadJson(wpi::raw_istream& is, std::string_view filename) {
+bool FieldInfo::LoadJson(std::span<const char> is, std::string_view filename) {
   // parse file
   wpi::json j;
   try {
-    j = wpi::json::parse(is);
+    j = wpi::json::parse({is.data(), is.size()});
   } catch (const wpi::json::parse_error& e) {
     fmt::print(stderr, "GUI: JSON: could not parse: {}\n", e.what());
     return false;
@@ -532,12 +531,15 @@ bool FieldInfo::LoadJson(wpi::raw_istream& is, std::string_view filename) {
 
 void FieldInfo::LoadJsonFile(std::string_view jsonfile) {
   std::error_code ec;
-  wpi::raw_fd_istream f(jsonfile, ec);
-  if (ec) {
+  std::unique_ptr<wpi::MemoryBuffer> fileBuffer =
+      wpi::MemoryBuffer::GetFile(jsonfile, ec);
+  if (fileBuffer == nullptr || ec) {
     std::fputs("GUI: could not open field JSON file\n", stderr);
     return;
   }
-  LoadJson(f, jsonfile);
+  LoadJson(
+      {reinterpret_cast<const char*>(fileBuffer->begin()), fileBuffer->size()},
+      jsonfile);
 }
 
 bool FieldInfo::LoadImageImpl(const std::string& fn) {
diff --git a/ntcore/src/main/native/cpp/NetworkServer.cpp b/ntcore/src/main/native/cpp/NetworkServer.cpp
index f3e26535df..e8bfd16669 100644
--- a/ntcore/src/main/native/cpp/NetworkServer.cpp
+++ b/ntcore/src/main/native/cpp/NetworkServer.cpp
@@ -11,11 +11,11 @@
 #include <system_error>
 #include <vector>
 
+#include <wpi/MemoryBuffer.h>
 #include <wpi/SmallString.h>
 #include <wpi/StringExtras.h>
 #include <wpi/fs.h>
 #include <wpi/mutex.h>
-#include <wpi/raw_istream.h>
 #include <wpi/raw_ostream.h>
 #include <wpinet/HttpUtil.h>
 #include <wpinet/HttpWebSocketServerConnection.h>
@@ -310,9 +310,9 @@ void NetworkServer::HandleLocal() {
 
 void NetworkServer::LoadPersistent() {
   std::error_code ec;
-  auto size = fs::file_size(m_persistentFilename, ec);
-  wpi::raw_fd_istream is{m_persistentFilename, ec};
-  if (ec.value() != 0) {
+  std::unique_ptr<wpi::MemoryBuffer> fileBuffer =
+      wpi::MemoryBuffer::GetFile(m_persistentFilename, ec);
+  if (fileBuffer == nullptr || ec.value() != 0) {
     INFO(
         "could not open persistent file '{}': {} "
         "(this can be ignored if you aren't expecting persistent values)",
@@ -325,12 +325,8 @@ void NetworkServer::LoadPersistent() {
     }
     return;
   }
-  is.readinto(m_persistentData, size);
+  m_persistentData = std::string{fileBuffer->begin(), fileBuffer->end()};
   DEBUG4("read data: {}", m_persistentData);
-  if (is.has_error()) {
-    WARN("error reading persistent file");
-    return;
-  }
 }
 
 void NetworkServer::SavePersistent(std::string_view filename,
diff --git a/simulation/halsim_ws_server/src/main/native/cpp/HALSimHttpConnection.cpp b/simulation/halsim_ws_server/src/main/native/cpp/HALSimHttpConnection.cpp
index ba4212171c..ee188b3208 100644
--- a/simulation/halsim_ws_server/src/main/native/cpp/HALSimHttpConnection.cpp
+++ b/simulation/halsim_ws_server/src/main/native/cpp/HALSimHttpConnection.cpp
@@ -9,10 +9,10 @@
 #include <string_view>
 
 #include <fmt/format.h>
+#include <wpi/MemoryBuffer.h>
 #include <wpi/SmallVector.h>
 #include <wpi/StringExtras.h>
 #include <wpi/fs.h>
-#include <wpi/raw_istream.h>
 #include <wpinet/MimeTypes.h>
 #include <wpinet/UrlParser.h>
 #include <wpinet/raw_uv_ostream.h>
@@ -125,8 +125,9 @@ void HALSimHttpConnection::SendFileResponse(int code, std::string_view codeText,
   }
 
   // open file
-  wpi::raw_fd_istream is{filename, ec, true};
-  if (ec) {
+  std::unique_ptr<wpi::MemoryBuffer> fileBuffer =
+      wpi::MemoryBuffer::GetFile(filename, ec);
+  if (fileBuffer == nullptr || ec) {
     MySendError(404, "error opening file");
     return;
   }
@@ -142,16 +143,7 @@ void HALSimHttpConnection::SendFileResponse(int code, std::string_view codeText,
   wpi::SmallVector<uv::Buffer, 4> bodyData;
   wpi::raw_uv_ostream bodyOs{bodyData, 4096};
 
-  std::string fileBuf;
-  size_t oldSize = 0;
-
-  while (fileBuf.size() < size) {
-    oldSize = fileBuf.size();
-    fileBuf.resize(oldSize + 1);
-    is.read(&(*fileBuf.begin()) + oldSize, 1);
-  }
-
-  bodyOs << fileBuf;
+  bodyOs << fileBuffer->GetBuffer();
 
   SendData(bodyOs.bufs(), false);
   if (!m_keepAlive) {
diff --git a/wpimath/src/main/native/cpp/trajectory/TrajectoryUtil.cpp b/wpimath/src/main/native/cpp/trajectory/TrajectoryUtil.cpp
index 169b642a6c..23b17daf72 100644
--- a/wpimath/src/main/native/cpp/trajectory/TrajectoryUtil.cpp
+++ b/wpimath/src/main/native/cpp/trajectory/TrajectoryUtil.cpp
@@ -7,9 +7,9 @@
 #include <system_error>
 
 #include <fmt/format.h>
+#include <wpi/MemoryBuffer.h>
 #include <wpi/SmallString.h>
 #include <wpi/json.h>
-#include <wpi/raw_istream.h>
 #include <wpi/raw_ostream.h>
 
 using namespace frc;
@@ -29,15 +29,14 @@ void TrajectoryUtil::ToPathweaverJson(const Trajectory& trajectory,
 }
 
 Trajectory TrajectoryUtil::FromPathweaverJson(std::string_view path) {
-  std::error_code error_code;
-
-  wpi::raw_fd_istream input{path, error_code};
-  if (error_code) {
+  std::error_code ec;
+  std::unique_ptr<wpi::MemoryBuffer> fileBuffer =
+      wpi::MemoryBuffer::GetFile(path, ec);
+  if (fileBuffer == nullptr || ec) {
     throw std::runtime_error(fmt::format("Cannot open file: {}", path));
   }
 
-  wpi::json json;
-  input >> json;
+  wpi::json json = wpi::json::parse({fileBuffer->begin(), fileBuffer->end()});
 
   return Trajectory{json.get<std::vector<Trajectory::State>>()};
 }