diff --git a/CMakeLists.txt b/CMakeLists.txt
index a3b944532..dfc180c76 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -312,7 +312,7 @@ endif()
 # boost::process was introduced first in version 1.64.0,
 # boost::beast::detail::base64 was introduced first in version 1.66.0
 set(MINIMUM_BOOST_VERSION "1.66.0")
-set(_boost_components "system;filesystem;thread;log;locale;regex;chrono;atomic;date_time")
+set(_boost_components "system;filesystem;thread;log;locale;regex;chrono;atomic;date_time;iostreams")
 find_package(Boost ${MINIMUM_BOOST_VERSION} REQUIRED COMPONENTS ${_boost_components})
 
 add_library(boost_libs INTERFACE)
diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index aef6222a3..d7e72b4ad 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -757,8 +757,16 @@ void GCode::do_export(Print* print, const char* path, GCodeProcessor::Result* re
     BOOST_LOG_TRIVIAL(debug) << "Start processing gcode, " << log_memory_info();
     m_processor.process_file(path_tmp, true, [print]() { print->throw_if_canceled(); });
     DoExport::update_print_estimated_times_stats(m_processor, print->m_print_statistics);
+#if ENABLE_GCODE_WINDOW
+    if (result != nullptr) {
+        *result = std::move(m_processor.extract_result());
+        // set the filename to the correct value
+        result->filename = path;
+    }
+#else
     if (result != nullptr)
         *result = std::move(m_processor.extract_result());
+#endif // ENABLE_GCODE_WINDOW
     BOOST_LOG_TRIVIAL(debug) << "Finished processing gcode, " << log_memory_info();
 
     if (rename_file(path_tmp, path))
diff --git a/src/libslic3r/GCode/GCodeProcessor.cpp b/src/libslic3r/GCode/GCodeProcessor.cpp
index 73ad25496..bd4e7a3ad 100644
--- a/src/libslic3r/GCode/GCodeProcessor.cpp
+++ b/src/libslic3r/GCode/GCodeProcessor.cpp
@@ -9,6 +9,9 @@
 #endif // ENABLE_VALIDATE_CUSTOM_GCODE
 #include <boost/nowide/fstream.hpp>
 #include <boost/nowide/cstdio.hpp>
+#if ENABLE_GCODE_WINDOW
+#include <boost/filesystem/path.hpp>
+#endif // ENABLE_GCODE_WINDOW
 
 #include <float.h>
 #include <assert.h>
@@ -974,6 +977,9 @@ void GCodeProcessor::process_file(const std::string& filename, bool apply_postpr
     }
 
     // process gcode
+#if ENABLE_GCODE_WINDOW
+    m_result.filename = filename;
+#endif // ENABLE_GCODE_WINDOW
     m_result.id = ++s_result_id;
     // 1st move must be a dummy move
     m_result.moves.emplace_back(MoveVertex());
diff --git a/src/libslic3r/GCode/GCodeProcessor.hpp b/src/libslic3r/GCode/GCodeProcessor.hpp
index c1497edda..f6625452f 100644
--- a/src/libslic3r/GCode/GCodeProcessor.hpp
+++ b/src/libslic3r/GCode/GCodeProcessor.hpp
@@ -337,13 +337,15 @@ namespace Slic3r {
                 std::vector<std::string> filament;
                 std::string printer;
 
-                void reset()
-                {
+                void reset() {
                     print = "";
                     filament = std::vector<std::string>();
                     printer = "";
                 }
             };
+#if ENABLE_GCODE_WINDOW
+            std::string filename;
+#endif // ENABLE_GCODE_WINDOW
             unsigned int id;
             std::vector<MoveVertex> moves;
             Pointfs bed_shape;
diff --git a/src/libslic3r/Technologies.hpp b/src/libslic3r/Technologies.hpp
index 55de9637a..63ee79805 100644
--- a/src/libslic3r/Technologies.hpp
+++ b/src/libslic3r/Technologies.hpp
@@ -53,6 +53,8 @@
 #define ENABLE_GCODE_LINES_ID_IN_H_SLIDER (1 && ENABLE_2_3_1_ALPHA1)
 // Enable validation of custom gcode against gcode processor reserved keywords
 #define ENABLE_VALIDATE_CUSTOM_GCODE (1 && ENABLE_2_3_1_ALPHA1)
+// Enable showing a imgui window containing gcode in preview
+#define ENABLE_GCODE_WINDOW (1 && ENABLE_2_3_1_ALPHA1)
 
 
 #endif // _prusaslicer_technologies_h_
diff --git a/src/slic3r/GUI/GCodeViewer.cpp b/src/slic3r/GUI/GCodeViewer.cpp
index 66762eaee..17e3ac68c 100644
--- a/src/slic3r/GUI/GCodeViewer.cpp
+++ b/src/slic3r/GUI/GCodeViewer.cpp
@@ -21,6 +21,9 @@
 
 #include <GL/glew.h>
 #include <boost/log/trivial.hpp>
+#if ENABLE_GCODE_WINDOW
+#include <boost/algorithm/string/split.hpp>
+#endif // ENABLE_GCODE_WINDOW
 #include <boost/nowide/cstdio.hpp>
 #include <wx/progdlg.h>
 #include <wx/numformatter.h>
@@ -280,7 +283,7 @@ void GCodeViewer::SequentialView::Marker::render() const
     imgui.text_colored(ImGuiWrapper::COL_ORANGE_LIGHT, _u8L("Tool position") + ":");
     ImGui::SameLine();
     char buf[1024];
-    sprintf(buf, "X: %.2f, Y: %.2f, Z: %.2f", m_world_position(0), m_world_position(1), m_world_position(2));
+    sprintf(buf, "X: %.3f, Y: %.3f, Z: %.3f", m_world_position(0), m_world_position(1), m_world_position(2));
     imgui.text(std::string(buf));
 
     // force extra frame to automatically update window size
@@ -297,6 +300,223 @@ void GCodeViewer::SequentialView::Marker::render() const
     ImGui::PopStyleVar();
 }
 
+#if ENABLE_GCODE_WINDOW
+void GCodeViewer::SequentialView::GCodeWindow::load_gcode()
+{
+    if (m_filename.empty())
+        return;
+
+    try
+    {
+        // generate mapping for accessing data in file by line number
+        boost::nowide::ifstream f(m_filename);
+
+        f.seekg(0, f.end);
+        uint64_t file_length = static_cast<uint64_t>(f.tellg());
+        f.seekg(0, f.beg);
+
+        std::string line;
+        uint64_t offset = 0;
+        while (std::getline(f, line)) {
+            uint64_t line_length = static_cast<uint64_t>(line.length());
+            m_lines_map.push_back({ offset, line_length });
+            offset += static_cast<uint64_t>(line_length) + 1;
+        }
+
+        if (offset != file_length) {
+            // if the final offset does not match with file length, lines are terminated with CR+LF
+            // so update all offsets accordingly
+            for (size_t i = 0; i < m_lines_map.size(); ++i) {
+                m_lines_map[i].first += static_cast<uint64_t>(i);
+            }
+        }
+    }
+    catch (...)
+    {
+        BOOST_LOG_TRIVIAL(error) << "Unable to load data from " << m_filename << ". Cannot show G-code window.";
+        reset();
+        return;
+    }
+
+    m_selected_line_id = 0;
+    m_last_lines_size = 0;
+
+    try
+    {
+        m_file.open(boost::filesystem::path(m_filename));
+    }
+    catch (...)
+    {
+        BOOST_LOG_TRIVIAL(error) << "Unable to map file " << m_filename << ". Cannot show G-code window.";
+        reset();
+    }
+}
+
+void GCodeViewer::SequentialView::GCodeWindow::render(float top, float bottom, uint64_t curr_line_id) const
+{
+    auto update_lines = [this](uint64_t start_id, uint64_t end_id) {
+        std::vector<Line> ret;
+        ret.reserve(end_id - start_id + 1);
+        for (uint64_t id = start_id; id <= end_id; ++id) {
+            // read line from file
+            std::string gline(m_file.data() + m_lines_map[id - 1].first, m_lines_map[id - 1].second);
+
+            std::string command;
+            std::string parameters;
+            std::string comment;
+
+            // extract comment
+            std::vector<std::string> tokens;
+            boost::split(tokens, gline, boost::is_any_of(";"), boost::token_compress_on);
+            command = tokens.front();
+            if (tokens.size() > 1)
+                comment = ";" + tokens.back();
+
+            // extract gcode command and parameters
+            if (!command.empty()) {
+                boost::split(tokens, command, boost::is_any_of(" "), boost::token_compress_on);
+                command = tokens.front();
+                if (tokens.size() > 1) {
+                    for (size_t i = 1; i < tokens.size(); ++i) {
+                        parameters += " " + tokens[i];
+                    }
+                }
+            }
+            ret.push_back({ command, parameters, comment });
+        }
+        return ret;
+    };
+
+    static const ImVec4 LINE_NUMBER_COLOR = ImGuiWrapper::COL_ORANGE_LIGHT;
+    static const ImVec4 SELECTION_RECT_COLOR = ImGuiWrapper::COL_ORANGE_DARK;
+    static const ImVec4 COMMAND_COLOR = { 0.8f, 0.8f, 0.0f, 1.0f };
+    static const ImVec4 PARAMETERS_COLOR = { 1.0f, 1.0f, 1.0f, 1.0f };
+    static const ImVec4 COMMENT_COLOR = { 0.7f, 0.7f, 0.7f, 1.0f };
+
+    if (!m_visible || m_filename.empty() || m_lines_map.empty() || curr_line_id == 0)
+        return;
+
+    // window height
+    const float wnd_height = bottom - top;
+
+    // number of visible lines
+    const float text_height = ImGui::CalcTextSize("0").y;
+    const ImGuiStyle& style = ImGui::GetStyle();
+    const uint64_t lines_count = static_cast<uint64_t>((wnd_height - 2.0f * style.WindowPadding.y + style.ItemSpacing.y) / (text_height + style.ItemSpacing.y));
+
+    if (lines_count == 0)
+        return;
+
+    // visible range
+    const uint64_t half_lines_count = lines_count / 2;
+    uint64_t start_id = (curr_line_id >= half_lines_count) ? curr_line_id - half_lines_count : 0;
+    uint64_t end_id = start_id + lines_count - 1;
+    if (end_id >= static_cast<uint64_t>(m_lines_map.size())) {
+        end_id = static_cast<uint64_t>(m_lines_map.size()) - 1;
+        start_id = end_id - lines_count + 1;
+    }
+
+    // updates list of lines to show, if needed
+    if (m_selected_line_id != curr_line_id || m_last_lines_size != end_id - start_id + 1) {
+        try
+        {
+            *const_cast<std::vector<Line>*>(&m_lines) = update_lines(start_id, end_id);
+        }
+        catch (...)
+        {
+            BOOST_LOG_TRIVIAL(error) << "Error while loading from file " << m_filename << ". Cannot show G-code window.";
+            return;
+        }
+        *const_cast<uint64_t*>(&m_selected_line_id) = curr_line_id;
+        *const_cast<size_t*>(&m_last_lines_size) = m_lines.size();
+    }
+
+    // line number's column width
+    const float id_width = ImGui::CalcTextSize(std::to_string(end_id).c_str()).x;
+
+    ImGuiWrapper& imgui = *wxGetApp().imgui();
+
+    imgui.set_next_window_pos(0.0f, top, ImGuiCond_Always, 0.0f, 0.0f);
+    imgui.set_next_window_size(0.0f, wnd_height, ImGuiCond_Always);
+    ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
+    ImGui::SetNextWindowBgAlpha(0.6f);
+    imgui.begin(std::string("G-code"), ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoDecoration | ImGuiWindowFlags_NoMove);
+   
+    // center the text in the window by pushing down the first line
+    const float f_lines_count = static_cast<float>(lines_count);
+    ImGui::SetCursorPosY(0.5f * (wnd_height - f_lines_count * text_height - (f_lines_count - 1.0f) * style.ItemSpacing.y));
+
+    // render text lines
+    for (uint64_t id = start_id; id <= end_id; ++id) {
+        const Line& line = m_lines[id - start_id];
+
+        // rect around the current selected line
+        if (id == curr_line_id) {
+            const float pos_y = ImGui::GetCursorScreenPos().y;
+            const float half_ItemSpacing_y = 0.5f * style.ItemSpacing.y;
+            const float half_padding_x = 0.5f * style.WindowPadding.x;
+            ImGui::GetWindowDrawList()->AddRect({ half_padding_x, pos_y - half_ItemSpacing_y },
+                { ImGui::GetCurrentWindow()->Size.x - half_padding_x, pos_y + text_height + half_ItemSpacing_y },
+                ImGui::GetColorU32(SELECTION_RECT_COLOR));
+        }
+
+        // render line number
+        const std::string id_str = std::to_string(id);
+        // spacer to right align text
+        ImGui::Dummy({ id_width - ImGui::CalcTextSize(id_str.c_str()).x, text_height });
+        ImGui::SameLine(0.0f, 0.0f);
+        ImGui::PushStyleColor(ImGuiCol_Text, LINE_NUMBER_COLOR);
+        imgui.text(id_str);
+        ImGui::PopStyleColor();
+
+        if (!line.command.empty() || !line.comment.empty())
+            ImGui::SameLine();
+
+        // render command
+        if (!line.command.empty()) {
+            ImGui::PushStyleColor(ImGuiCol_Text, COMMAND_COLOR);
+            imgui.text(line.command);
+            ImGui::PopStyleColor();
+        }
+
+        // render parameters
+        if (!line.parameters.empty()) {
+            ImGui::SameLine(0.0f, 0.0f);
+            ImGui::PushStyleColor(ImGuiCol_Text, PARAMETERS_COLOR);
+            imgui.text(line.parameters);
+            ImGui::PopStyleColor();
+        }
+
+        // render comment
+        if (!line.comment.empty()) {
+            if (!line.command.empty())
+                ImGui::SameLine(0.0f, 0.0f);
+            ImGui::PushStyleColor(ImGuiCol_Text, COMMENT_COLOR);
+            imgui.text(line.comment);
+            ImGui::PopStyleColor();
+        }
+    }
+
+    imgui.end();
+    ImGui::PopStyleVar();
+}
+
+void GCodeViewer::SequentialView::GCodeWindow::stop_mapping_file()
+{
+    if (m_file.is_open())
+        m_file.close();
+}
+
+void GCodeViewer::SequentialView::render(float legend_height) const
+{
+    marker.render();
+    float bottom = wxGetApp().plater()->get_current_canvas3D()->get_canvas_size().get_height();
+    if (wxGetApp().is_editor())
+        bottom -= wxGetApp().plater()->get_view_toolbar().get_height();
+    gcode_window.render(legend_height, bottom, static_cast<uint64_t>(gcode_ids[current.last]));
+}
+#endif // ENABLE_GCODE_WINDOW
+
 const std::vector<GCodeViewer::Color> GCodeViewer::Extrusion_Role_Colors {{
     { 0.75f, 0.75f, 0.75f },   // erNone
     { 1.00f, 0.90f, 0.30f },   // erPerimeter
@@ -395,6 +615,11 @@ void GCodeViewer::load(const GCodeProcessor::Result& gcode_result, const Print&
     // release gpu memory, if used
     reset();
 
+#if ENABLE_GCODE_WINDOW
+    m_sequential_view.gcode_window.set_filename(gcode_result.filename);
+    m_sequential_view.gcode_window.load_gcode();
+#endif // ENABLE_GCODE_WINDOW
+
     load_toolpaths(gcode_result);
 
     if (m_layers.empty())
@@ -548,7 +773,9 @@ void GCodeViewer::reset()
     m_layers_z_range = { 0, 0 };
     m_roles = std::vector<ExtrusionRole>();
     m_time_statistics.reset();
-
+#if ENABLE_GCODE_WINDOW
+    m_sequential_view.gcode_window.reset();
+#endif // ENABLE_GCODE_WINDOW
 #if ENABLE_GCODE_VIEWER_STATISTICS
     m_statistics.reset_all();
 #endif // ENABLE_GCODE_VIEWER_STATISTICS
@@ -608,13 +835,22 @@ void GCodeViewer::render() const
 
     glsafe(::glEnable(GL_DEPTH_TEST));
     render_toolpaths();
+    render_shells();
+#if ENABLE_GCODE_WINDOW
+    float legend_height = 0.0f;
+    render_legend(legend_height);
+#else
+    render_legend();
+#endif // ENABLE_GCODE_WINDOW
     SequentialView* sequential_view = const_cast<SequentialView*>(&m_sequential_view);
     if (sequential_view->current.last != sequential_view->endpoints.last) {
         sequential_view->marker.set_world_position(sequential_view->current_position);
+#if ENABLE_GCODE_WINDOW
+        sequential_view->render(legend_height);
+#else
         sequential_view->marker.render();
+#endif // ENABLE_GCODE_WINDOW
     }
-    render_shells();
-    render_legend();
 #if ENABLE_GCODE_VIEWER_STATISTICS
     render_statistics();
 #endif // ENABLE_GCODE_VIEWER_STATISTICS
@@ -3767,7 +4003,11 @@ void GCodeViewer::render_shells() const
 //    glsafe(::glDepthMask(GL_TRUE));
 }
 
+#if ENABLE_GCODE_WINDOW
+void GCodeViewer::render_legend(float& legend_height) const
+#else
 void GCodeViewer::render_legend() const
+#endif // ENABLE_GCODE_WINDOW
 {
     if (!m_legend_enabled)
         return;
@@ -4452,6 +4692,10 @@ void GCodeViewer::render_legend() const
         }
     }
 
+#if ENABLE_GCODE_WINDOW
+    legend_height = ImGui::GetCurrentWindow()->Size.y;
+#endif // ENABLE_GCODE_WINDOW
+
     imgui.end();
     ImGui::PopStyleVar();
 }
diff --git a/src/slic3r/GUI/GCodeViewer.hpp b/src/slic3r/GUI/GCodeViewer.hpp
index 2abbb81f1..cc897c7bc 100644
--- a/src/slic3r/GUI/GCodeViewer.hpp
+++ b/src/slic3r/GUI/GCodeViewer.hpp
@@ -5,6 +5,10 @@
 #include "libslic3r/GCode/GCodeProcessor.hpp"
 #include "GLModel.hpp"
 
+#if ENABLE_GCODE_WINDOW
+#include <boost/iostreams/device/mapped_file.hpp>
+#endif // ENABLE_GCODE_WINDOW
+
 #include <cstdint>
 #include <float.h>
 #include <set>
@@ -606,6 +610,46 @@ public:
             void render() const;
         };
 
+#if ENABLE_GCODE_WINDOW
+        class GCodeWindow
+        {
+            struct Line
+            {
+                std::string command;
+                std::string parameters;
+                std::string comment;
+            };
+            bool m_visible{ true };
+            uint64_t m_selected_line_id{ 0 };
+            size_t m_last_lines_size{ 0 };
+            std::string m_filename;
+            boost::iostreams::mapped_file_source m_file;
+            // map for accessing data in file by line number
+            std::vector<std::pair<uint64_t, uint64_t>> m_lines_map;
+            // current visible lines
+            std::vector<Line> m_lines;
+
+        public:
+            GCodeWindow() = default;
+            ~GCodeWindow() { stop_mapping_file(); }
+            void set_filename(const std::string& filename) { m_filename = filename; }
+            void load_gcode();
+            void reset() {
+                stop_mapping_file();
+                m_lines_map.clear();
+                m_lines.clear();
+                m_filename.clear();
+            }
+
+            void toggle_visibility() { m_visible = !m_visible; }
+
+            void render(float top, float bottom, uint64_t curr_line_id) const;
+
+        private:
+            void stop_mapping_file();
+        };
+#endif // ENABLE_GCODE_WINDOW
+
         struct Endpoints
         {
             size_t first{ 0 };
@@ -618,9 +662,16 @@ public:
         Endpoints last_current;
         Vec3f current_position{ Vec3f::Zero() };
         Marker marker;
+#if ENABLE_GCODE_WINDOW
+        GCodeWindow gcode_window;
+#endif // ENABLE_GCODE_WINDOW
 #if ENABLE_GCODE_LINES_ID_IN_H_SLIDER
         std::vector<unsigned int> gcode_ids;
 #endif // ENABLE_GCODE_LINES_ID_IN_H_SLIDER
+
+#if ENABLE_GCODE_WINDOW
+        void render(float legend_height) const;
+#endif // ENABLE_GCODE_WINDOW
     };
 
     enum class EViewType : unsigned char
@@ -715,13 +766,21 @@ public:
 
     void export_toolpaths_to_obj(const char* filename) const;
 
+#if ENABLE_GCODE_WINDOW
+    void toggle_gcode_window_visibility() { m_sequential_view.gcode_window.toggle_visibility(); }
+#endif // ENABLE_GCODE_WINDOW
+
 private:
     void load_toolpaths(const GCodeProcessor::Result& gcode_result);
     void load_shells(const Print& print, bool initialized);
     void refresh_render_paths(bool keep_sequential_current_first, bool keep_sequential_current_last) const;
     void render_toolpaths() const;
     void render_shells() const;
+#if ENABLE_GCODE_WINDOW
+    void render_legend(float& legend_height) const;
+#else
     void render_legend() const;
+#endif // ENABLE_GCODE_WINDOW
 #if ENABLE_GCODE_VIEWER_STATISTICS
     void render_statistics() const;
 #endif // ENABLE_GCODE_VIEWER_STATISTICS
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 5352e21b3..7bbdc72b1 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -2602,6 +2602,10 @@ void GLCanvas3D::on_char(wxKeyEvent& evt)
         case 'a': { post_event(SimpleEvent(EVT_GLCANVAS_ARRANGE)); break; }
         case 'B':
         case 'b': { zoom_to_bed(); break; }
+#if ENABLE_GCODE_WINDOW
+        case 'C':
+        case 'c': { m_gcode_viewer.toggle_gcode_window_visibility(); m_dirty = true; request_extra_frame(); break; }
+#endif // ENABLE_GCODE_WINDOW
         case 'E':
         case 'e': { m_labels.show(!m_labels.is_shown()); m_dirty = true; break; }
         case 'G':
diff --git a/src/slic3r/GUI/KBShortcutsDialog.cpp b/src/slic3r/GUI/KBShortcutsDialog.cpp
index a7363837e..1c451672c 100644
--- a/src/slic3r/GUI/KBShortcutsDialog.cpp
+++ b/src/slic3r/GUI/KBShortcutsDialog.cpp
@@ -196,6 +196,9 @@ void KBShortcutsDialog::fill_shortcuts()
         { "D", L("Horizontal slider - Move active thumb Right") },
         { "X", L("On/Off one layer mode of the vertical slider") },
         { "L", L("Show/Hide Legend and Estimated printing time") },
+#if ENABLE_GCODE_WINDOW
+        { "C", L("Show/Hide G-code window") },
+#endif // ENABLE_GCODE_WINDOW
     };
 
     m_full_shortcuts.push_back({ { _L("Preview"), "" }, preview_shortcuts });