diff --git a/CMakeLists.txt b/CMakeLists.txt
index ee4ab7831..3a23c26d2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -59,6 +59,45 @@ if(IOS)
     include(cmake/XcodeHelper.cmake)
 endif()
 
+if(EMSCRIPTEN)
+    # Web build (wasmga.me): no threads, so no cross-origin isolation is
+    # needed; libraries come from STK_WASM_PREFIX (see build.sh).
+    set(CMAKE_PREFIX_PATH "${STK_WASM_PREFIX}")
+    set(P "${STK_WASM_PREFIX}")
+    set(JPEG_INCLUDE_DIR "${P}/include")
+    set(JPEG_LIBRARY "${P}/lib/libjpeg.a")
+    set(PNG_PNG_INCLUDE_DIR "${P}/include")
+    set(PNG_LIBRARY "${P}/lib/libpng16.a")
+    set(ZLIB_INCLUDE_DIR "${P}/include")
+    set(ZLIB_LIBRARY "${P}/lib/libz.a")
+    set(FREETYPE_INCLUDE_DIRS "${P}/include/freetype2")
+    set(FREETYPE_LIBRARY "${P}/lib/libfreetype.a")
+    set(HARFBUZZ_INCLUDEDIR "${P}/include/harfbuzz")
+    set(HARFBUZZ_LIBRARY "${P}/lib/libharfbuzz.a")
+    set(CURL_INCLUDE_DIR "${P}/include")
+    set(CURL_LIBRARY "${P}/lib/libcurl.a")
+    set(OPENSSL_INCLUDE_DIR "${P}/include")
+    set(OPENSSL_CRYPTO_LIBRARY "${P}/lib/libcrypto.a")
+    set(OGGVORBIS_OGG_INCLUDE_DIR "${P}/include")
+    set(OGGVORBIS_VORBIS_INCLUDE_DIR "${P}/include")
+    set(OGGVORBIS_OGG_LIBRARY "${P}/lib/libogg.a")
+    set(OGGVORBIS_VORBISFILE_LIBRARY "${P}/lib/libvorbisfile.a")
+    set(OGGVORBIS_VORBIS_LIBRARY "${P}/lib/libvorbis.a")
+    set(USE_WIIUSE 0)
+    set(USE_DNS_C 1)
+    # Emscripten has no separate pthread library; the stubs are in libc.
+    set(PTHREAD_LIBRARY "-lc")
+    set(USE_SQLITE3 OFF)
+    set(USE_GLES2 1)
+    set(NO_SHADERC on)
+    set(BUILD_RECORDER OFF)
+    add_definitions(-DNO_IRR_COMPILE_WITH_X11_ -DNO_IRR_COMPILE_WITH_WAYLAND_DEVICE_ -DDISABLE_RPC)
+    set(WEB_FLAGS "-sUSE_SDL=2 -fwasm-exceptions -sSUPPORT_LONGJMP=wasm")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${WEB_FLAGS}")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${WEB_FLAGS}")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${WEB_FLAGS} -L${P}/lib -lopenal -sENVIRONMENT=web -sMIN_WEBGL_VERSION=2 -sMAX_WEBGL_VERSION=2 -sFULL_ES3 -sALLOW_MEMORY_GROWTH -sINITIAL_MEMORY=512MB -sMAXIMUM_MEMORY=4GB -sSTACK_SIZE=8MB -sINVOKE_RUN=0 -sEXIT_RUNTIME=0 -sEXPORTED_RUNTIME_METHODS=FS,callMain,ccall,cwrap,UTF8ToString -sEXPORTED_FUNCTIONS=_main -sWASM_BIGINT -sMODULARIZE=0")
+endif()
+
 if(APPLE AND NOT IOS)
     if(${CMAKE_SYSTEM_PROCESSOR} STREQUAL "arm")
 	set(ARCHFLAGS "arm64")
@@ -960,3 +999,8 @@ if(MINGW)
     install(DIRECTORY ${CMAKE_BINARY_DIR}/bin/ DESTINATION ${STK_INSTALL_BINARY_DIR}
             FILES_MATCHING PATTERN "*.dll")
 endif()
+
+if(EMSCRIPTEN)
+    # Static libraries link in order: vorbisfile needs vorbis and ogg after it.
+    target_link_libraries(supertuxkart "${STK_WASM_PREFIX}/lib/libvorbis.a" "${STK_WASM_PREFIX}/lib/libogg.a")
+endif()
diff --git a/data/gui/screens/options/options_display.stkgui b/data/gui/screens/options/options_display.stkgui
index dfa3ae762..63af8f18d 100644
--- a/data/gui/screens/options/options_display.stkgui
+++ b/data/gui/screens/options/options_display.stkgui
@@ -31,7 +31,7 @@
             <box width="78%" height="100%" layout="vertical-row">
 
                 <!-- ************ RESOLUTION CHOICE ************ -->
-                <label width="100%" I18N="In the display settings" text="Resolution"/>
+                <label id="resolutionText" width="100%" I18N="In the display settings" text="Resolution"/>
 
                 <spacer width="5" height="1%"/>
 
diff --git a/data/gui/screens/options/options_general.stkgui b/data/gui/screens/options/options_general.stkgui
index 3d726a66d..df1bc58f8 100644
--- a/data/gui/screens/options/options_general.stkgui
+++ b/data/gui/screens/options/options_general.stkgui
@@ -29,7 +29,7 @@
             <spacer width="2%" height="100%"/>
 
             <div width="100%" height="100%" layout="vertical-row" >
-                <box width="78%" height="62%" layout="vertical-row">
+                <box id="internet_box" width="78%" height="62%" layout="vertical-row">
 
                     <spacer width="5" height="2%"/>
 
diff --git a/data/gui/screens/options/user_screen_tab.stkgui b/data/gui/screens/options/user_screen_tab.stkgui
index b44369375..0b78a5c0e 100644
--- a/data/gui/screens/options/user_screen_tab.stkgui
+++ b/data/gui/screens/options/user_screen_tab.stkgui
@@ -40,7 +40,7 @@
                     <div width="100%" height="fit" layout="horizontal-row" >
                         <checkbox width="fit" id="online" I18N="In the user screen" text_align="left"/>
                         <spacer width="10"/>
-                        <label proportion="1" height="100%" text_align="left" I18N="In the user screen" text="Online"/>
+                        <label proportion="1" id="label_online" height="100%" text_align="left" I18N="In the user screen" text="Online"/>
                     </div>
                     <div width="100%" height="fit" layout="horizontal-row" >
                         <checkbox width="fit" id="remember-user" I18N="In the user screen" text_align="left"/>
diff --git a/data/gui/screens/user_screen.stkgui b/data/gui/screens/user_screen.stkgui
index d83a1a303..6ff42382e 100644
--- a/data/gui/screens/user_screen.stkgui
+++ b/data/gui/screens/user_screen.stkgui
@@ -16,7 +16,7 @@
                 <div width="100%" height="fit" layout="horizontal-row" >
                     <checkbox width="fit" id="online" I18N="In the user screen" text_align="left"/>
                     <spacer width="10"/>
-                    <label proportion="1" height="100%" text_align="left" I18N="In the user screen" text="Online"/>
+                    <label proportion="1" id="label_online" height="100%" text_align="left" I18N="In the user screen" text="Online"/>
                 </div>
                 <div width="100%" height="fit" layout="horizontal-row" >
                     <checkbox width="fit" id="remember-user" I18N="In the user screen" text_align="left"/>
diff --git a/lib/angelscript/projects/cmake/CMakeLists.txt b/lib/angelscript/projects/cmake/CMakeLists.txt
index baa26832c..78ad44bb3 100644
--- a/lib/angelscript/projects/cmake/CMakeLists.txt
+++ b/lib/angelscript/projects/cmake/CMakeLists.txt
@@ -191,7 +191,9 @@ endif()
 
 # Don't override the default library output path to avoid conflicts when building for multiple target platforms
 #set(LIBRARY_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/../../lib)
-target_link_libraries(${ANGELSCRIPT_LIBRARY_NAME} Threads::Threads)
+if(NOT EMSCRIPTEN)
+    target_link_libraries(${ANGELSCRIPT_LIBRARY_NAME} Threads::Threads)
+endif()
 
 set_target_properties(${ANGELSCRIPT_LIBRARY_NAME} PROPERTIES VERSION ${PROJECT_VERSION})
 
diff --git a/lib/enet/unix.c b/lib/enet/unix.c
index c10a3d99d..3f4e952b4 100644
--- a/lib/enet/unix.c
+++ b/lib/enet/unix.c
@@ -53,7 +53,7 @@
 #include <poll.h>
 #endif
 
-#ifndef HAS_SOCKLEN_T
+#if !defined(HAS_SOCKLEN_T) && !defined(__EMSCRIPTEN__)
 typedef int socklen_t;
 #endif
 
diff --git a/lib/graphics_engine/CMakeLists.txt b/lib/graphics_engine/CMakeLists.txt
index 081629bbb..5a9a282e6 100644
--- a/lib/graphics_engine/CMakeLists.txt
+++ b/lib/graphics_engine/CMakeLists.txt
@@ -42,10 +42,12 @@ include_directories("${PROJECT_SOURCE_DIR}/lib/graphics_utils")
 include_directories("${PROJECT_SOURCE_DIR}/lib/irrlicht/include")
 include_directories("${PROJECT_SOURCE_DIR}/lib/bullet/src")
 find_path(SDL2_INCLUDEDIR NAMES SDL.h PATH_SUFFIXES SDL2 include/SDL2 include PATHS)
-if (NOT SDL2_INCLUDEDIR)
-    message(FATAL_ERROR "SDL2 not found.")
-else()
-    include_directories("${SDL2_INCLUDEDIR}")
+if (NOT EMSCRIPTEN)
+    if (NOT SDL2_INCLUDEDIR)
+        message(FATAL_ERROR "SDL2 not found.")
+    else()
+        include_directories("${SDL2_INCLUDEDIR}")
+    endif()
 endif()
 
 if(APPLE AND NOT DLOPEN_MOLTENVK)
diff --git a/lib/graphics_engine/src/ge_gl_texture.cpp b/lib/graphics_engine/src/ge_gl_texture.cpp
index 1774f28da..8c29f9db0 100644
--- a/lib/graphics_engine/src/ge_gl_texture.cpp
+++ b/lib/graphics_engine/src/ge_gl_texture.cpp
@@ -58,6 +58,7 @@ GEGLTexture::GEGLTexture(const std::string& name, unsigned int size,
     m_size = m_orig_size;
 
     bool texture_swizzle = false;
+#ifndef __EMSCRIPTEN__
     if (m_driver_type == video::EDT_OGLES2)
     {
         int gl_major_version = 0;
@@ -72,6 +73,7 @@ GEGLTexture::GEGLTexture(const std::string& name, unsigned int size,
         texture_swizzle = irr::video::useCoreContext &&
             GE::hasGLExtension("GL_ARB_texture_swizzle");
     }
+#endif
 
     if (single_channel && texture_swizzle)
         m_single_channel = true;
diff --git a/lib/irrlicht/source/Irrlicht/CIrrDeviceSDL.cpp b/lib/irrlicht/source/Irrlicht/CIrrDeviceSDL.cpp
index 9bbeb96b1..99f107be7 100644
--- a/lib/irrlicht/source/Irrlicht/CIrrDeviceSDL.cpp
+++ b/lib/irrlicht/source/Irrlicht/CIrrDeviceSDL.cpp
@@ -106,7 +106,12 @@ CIrrDeviceSDL::CIrrDeviceSDL(const SIrrlichtCreationParameters& param)
 	}
 #endif
 
+#ifdef __EMSCRIPTEN__
+	// No threads, so no SDL timer.
+	u32 init_flags = SDL_INIT_VIDEO;
+#else
 	u32 init_flags = SDL_INIT_TIMER | SDL_INIT_VIDEO;
+#endif
 	if (SDL_InitSubSystem(init_flags) < 0)
 	{
 		os::Printer::log("Unable to initialize SDL!", SDL_GetError());
@@ -238,8 +243,11 @@ CIrrDeviceSDL::~CIrrDeviceSDL()
 	if (Window)
 		SDL_DestroyWindow(Window);
 		
-	u32 flags = SDL_INIT_TIMER | SDL_INIT_VIDEO;
-	SDL_QuitSubSystem(flags);
+#ifdef __EMSCRIPTEN__
+	SDL_QuitSubSystem(SDL_INIT_VIDEO);
+#else
+	SDL_QuitSubSystem(SDL_INIT_TIMER | SDL_INIT_VIDEO);
+#endif
 }
 
 
diff --git a/lib/irrlicht/source/Irrlicht/COGLES2Driver.cpp b/lib/irrlicht/source/Irrlicht/COGLES2Driver.cpp
index 2b81c554a..e28243e68 100644
--- a/lib/irrlicht/source/Irrlicht/COGLES2Driver.cpp
+++ b/lib/irrlicht/source/Irrlicht/COGLES2Driver.cpp
@@ -82,6 +82,9 @@ namespace video
 		egl_params.platform = CEGL_PLATFORM_DEFAULT;
 		egl_params.window = ((struct android_app *)(params.PrivateData))->window;
 		egl_params.display = NULL;
+#elif defined(__EMSCRIPTEN__)
+		egl_params.platform = CEGL_PLATFORM_DEFAULT;
+		egl_params.display = NULL;
 #endif
 
 		EglContext->init(egl_params);
diff --git a/src/audio/sfx_manager.cpp b/src/audio/sfx_manager.cpp
index ce6b66236..ba7ea712b 100644
--- a/src/audio/sfx_manager.cpp
+++ b/src/audio/sfx_manager.cpp
@@ -95,7 +95,7 @@ SFXManager::SFXManager()
     {
         // The thread is created even if there atm sfx are disabled
         // (since the user might enable it later).
-#ifndef __SWITCH__
+#if !defined(__SWITCH__) && !defined(__EMSCRIPTEN__)
         m_thread = std::thread(std::bind(mainLoop, this));
 #endif
         setMasterSFXVolume( UserConfigParams::m_sfx_volume );
@@ -111,7 +111,7 @@ SFXManager::SFXManager()
  */
 SFXManager::~SFXManager()
 {
-#if defined(ENABLE_SOUND) && !defined(__SWITCH__)
+#if defined(ENABLE_SOUND) && !defined(__SWITCH__) && !defined(__EMSCRIPTEN__)
     if (UserConfigParams::m_enable_sound)
     {
         m_thread.join();
@@ -348,19 +348,19 @@ void SFXManager::mainLoop(void *obj)
     if (!UserConfigParams::m_enable_sound)
         return;
         
-#ifndef __SWITCH__
+#if !defined(__SWITCH__) && !defined(__EMSCRIPTEN__)
     VS::setThreadName("SFXManager");
 #endif
     SFXManager *me = (SFXManager*)obj;
 
     std::unique_lock<std::mutex> ul = me->m_sfx_commands.acquireMutex();
 
-#ifdef __SWITCH__
+#if defined(__SWITCH__) || defined(__EMSCRIPTEN__)
     int iterCount = 0;
 #endif
     // Wait till we have an empty sfx in the queue
     while (
-#ifdef __SWITCH__
+#if defined(__SWITCH__) || defined(__EMSCRIPTEN__)
            // Don't spend too much time working on audio
            ++iterCount != 30 && !me->m_sfx_commands.getData().empty()
 #else
@@ -374,7 +374,7 @@ void SFXManager::mainLoop(void *obj)
         // Wait in cond_wait for a request to arrive. The 'while' is necessary
         // since "spurious wakeups from the pthread_cond_wait ... may occur"
         // (pthread_cond_wait man page)!
-#ifndef __SWITCH__
+#if !defined(__SWITCH__) && !defined(__EMSCRIPTEN__)
         while (empty)
         {
             me->m_condition_variable.wait(ul);
@@ -387,7 +387,7 @@ void SFXManager::mainLoop(void *obj)
         if (current->m_command == SFX_EXIT)
         {
             delete current;
-#ifdef __SWITCH__
+#if defined(__SWITCH__) || defined(__EMSCRIPTEN__)
             return;
 #else
             break;
@@ -464,6 +464,7 @@ void SFXManager::mainLoop(void *obj)
         current = NULL;
         PROFILER_POP_CPU_MARKER();
         PROFILER_PUSH_CPU_MARKER("yield", 0, 0, 255);
+#ifndef __EMSCRIPTEN__
         if (empty_queue && me->sfxAllowed())
         {
             // Wait some time to let other threads run, then queue an
@@ -473,6 +474,7 @@ void SFXManager::mainLoop(void *obj)
             t = StkTime::getMonoTimeMs() - t;
             me->queue(SFX_UPDATE, (SFXBase*)NULL, float(t / 1000.0));
         }
+#endif
         ul = me->m_sfx_commands.acquireMutex();
         PROFILER_POP_CPU_MARKER();
     }   // while
@@ -482,7 +484,7 @@ void SFXManager::mainLoop(void *obj)
     // need to keep the user waiting for STK to exit.
     me->setCanBeDeleted();
 
-#ifndef __SWITCH__
+#if !defined(__SWITCH__) && !defined(__EMSCRIPTEN__)
     // Clean up memory to avoid leak detection
     while(!me->m_sfx_commands.getData().empty())
     {
@@ -808,7 +810,7 @@ void SFXManager::update()
     // Wake up the sfx thread to handle all queued up audio commands.
     m_condition_variable.notify_one();
 
-#ifdef __SWITCH__
+#if defined(__SWITCH__) || defined(__EMSCRIPTEN__)
     mainLoop(this);
 #endif
 #endif
diff --git a/src/graphics/central_settings.cpp b/src/graphics/central_settings.cpp
index 5e353fa87..257980f4d 100644
--- a/src/graphics/central_settings.cpp
+++ b/src/graphics/central_settings.cpp
@@ -453,6 +453,10 @@ bool CentralVideoSettings::isTextureCompressionEnabled() const
     // MOBILE_STK currently doesn't handle libsquish in SP
     return false;
 #else
+#ifdef __EMSCRIPTEN__
+    // Compressing on the CPU without threads stalls every load.
+    return false;
+#endif
     return supportsTextureCompression() && UserConfigParams::m_texture_compression;
 #endif
 }
diff --git a/src/graphics/cpu_particle_manager.cpp b/src/graphics/cpu_particle_manager.cpp
index 203a19e75..7c4e42f4e 100644
--- a/src/graphics/cpu_particle_manager.cpp
+++ b/src/graphics/cpu_particle_manager.cpp
@@ -17,6 +17,11 @@
 
 
 #include "graphics/cpu_particle_manager.hpp"
+#ifdef __EMSCRIPTEN__
+#include "graphics/rtts.hpp"
+#include "graphics/shader_based_renderer.hpp"
+#include "graphics/sp/sp_base.hpp"
+#endif
 #include "graphics/stk_particle.hpp"
 #include "graphics/irr_driver.hpp"
 #include "graphics/material.hpp"
@@ -33,6 +38,12 @@
 
 #include "graphics/texture_shader.hpp"
 
+#ifdef __EMSCRIPTEN__
+// WebGL maps buffers by copying, and only takes write + invalidate.
+#undef GL_MAP_UNSYNCHRONIZED_BIT
+#define GL_MAP_UNSYNCHRONIZED_BIT 0
+#endif
+
 // ============================================================================
 /** A Shader to render particles.
 */
@@ -387,7 +398,11 @@ void CPUParticleManager::drawAll()
             ParticleRenderer::getInstance()->setTextureUnits
                 (cur_mat->getTexture()->getTextureHandler(),
                 CVS->isDeferredEnabled() ?
+#ifdef __EMSCRIPTEN__
+                SP::getRenderer()->getRTTs()->getDepthCopyTexture() : 0);
+#else
                 irr_driver->getDepthStencilTexture() : 0);
+#endif
             ParticleRenderer::getInstance()->setUniforms(flips, sky,
                 view_position, billboard);
         }
diff --git a/src/graphics/draw_calls.hpp b/src/graphics/draw_calls.hpp
index 6fd7f7e79..296d69b9f 100644
--- a/src/graphics/draw_calls.hpp
+++ b/src/graphics/draw_calls.hpp
@@ -64,7 +64,13 @@ public:
 
     void renderBoundingBoxes();
 
+#ifdef __EMSCRIPTEN__
+    // WebGL can't wait on a fence (and calling glClientWaitSync through its
+    // pointer traps), so frames aren't synced.
+    void setFenceSync() {}
+#else
     void setFenceSync() { m_sync = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0); }
+#endif
 };
 
 #endif   // !SERVER_ONLY
diff --git a/src/graphics/irr_driver.cpp b/src/graphics/irr_driver.cpp
index 9ee8dd6e7..643cd180d 100644
--- a/src/graphics/irr_driver.cpp
+++ b/src/graphics/irr_driver.cpp
@@ -408,6 +408,10 @@ void IrrDriver::createListOfVideoModes()
  */
 void IrrDriver::initDevice()
 {
+#ifdef __EMSCRIPTEN__
+    // The page owns full screen.
+    UserConfigParams::m_fullscreen = false;
+#endif
 #if !defined(SERVER_ONLY)
     std::string abs_shader_dir = file_manager->getFileSystem()
         ->getAbsolutePath(file_manager->getShadersDir().c_str()).c_str();
@@ -733,6 +737,21 @@ begin:
         GE::setVideoDriver(m_device->getVideoDriver());
         CVS->init();
     }
+#endif
+#if defined(__EMSCRIPTEN__) && !defined(SERVER_ONLY)
+    // Until the real uniform buffers exist, give the loading screen's
+    // shaders a blank one, so WebGL draws it.
+    if (!GUIEngine::isNoGraphics() && CVS->isGLSL())
+    {
+        GLuint blank;
+        glGenBuffers(1, &blank);
+        glBindBuffer(GL_UNIFORM_BUFFER, blank);
+        std::vector<char> zeros(16384);
+        glBufferData(GL_UNIFORM_BUFFER, zeros.size(), zeros.data(), GL_STATIC_DRAW);
+        glBindBuffer(GL_UNIFORM_BUFFER, 0);
+        for (GLuint i = 0; i < 3; i++)
+            glBindBufferBase(GL_UNIFORM_BUFFER, i, blank);
+    }
 #endif
     m_logger_level = irr::ELL_WARNING;
 
@@ -2201,6 +2220,17 @@ void IrrDriver::update(float dt, bool is_loading)
     if (CVS->isGLSL())
     {
         SP::SPTextureManager::get()->checkForGLCommand();
+#ifdef __EMSCRIPTEN__
+        // WebGL refuses to draw with a shader whose uniform blocks have no
+        // buffer bound, and the menus' shaders declare them too.
+        if (CVS->isARBUniformBufferObjectUsable())
+        {
+            glBindBufferBase(GL_UNIFORM_BUFFER, 0,
+                SP::sp_mat_ubo[SP::sp_cur_player][SP::sp_cur_buf_id[SP::sp_cur_player]]);
+            glBindBufferBase(GL_UNIFORM_BUFFER, 1, SharedGPUObjects::getLightingDataUBO());
+            glBindBufferBase(GL_UNIFORM_BUFFER, 2, SP::sp_fog_ubo);
+        }
+#endif
     }
 #endif
     World *world = World::getWorld();
diff --git a/src/graphics/rtts.cpp b/src/graphics/rtts.cpp
index ea14fd3ff..3f7581dc6 100644
--- a/src/graphics/rtts.cpp
+++ b/src/graphics/rtts.cpp
@@ -79,6 +79,13 @@ RTT::RTT(unsigned int width, unsigned int height, float rtt_scale,
     if (!use_default_fbo_only)
     {
         m_depth_stencil_tex = generateRTT(res, GL_DEPTH24_STENCIL8, GL_DEPTH_STENCIL, GL_UNSIGNED_INT_24_8);
+#ifdef __EMSCRIPTEN__
+        m_depth_copy_tex = generateRTT(res, GL_DEPTH24_STENCIL8, GL_DEPTH_STENCIL, GL_UNSIGNED_INT_24_8);
+        glGenFramebuffers(1, &m_depth_copy_fbo);
+        glBindFramebuffer(GL_FRAMEBUFFER, m_depth_copy_fbo);
+        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT,
+            GL_TEXTURE_2D, m_depth_copy_tex, 0);
+#endif
     }
 
     // All RTTs are currently RGBA16F mostly with stencil. The four tmp RTTs are the same size
@@ -194,7 +201,13 @@ RTT::RTT(unsigned int width, unsigned int height, float rtt_scale,
         somevector.clear();
         somevector.push_back(m_render_target_textures[RTT_DIFFUSE]);
         somevector.push_back(m_render_target_textures[RTT_SPECULAR]);
+#ifdef __EMSCRIPTEN__
+        // The lights read the depth texture, and WebGL won't draw while it
+        // is also attached.
+        m_frame_buffers[FBO_COMBINED_DIFFUSE_SPECULAR] = new FrameBuffer(somevector, res.Width, res.Height);
+#else
         m_frame_buffers[FBO_COMBINED_DIFFUSE_SPECULAR] = new FrameBuffer(somevector, m_depth_stencil_tex, res.Width, res.Height);
+#endif
 
         somevector.clear();
         somevector.push_back(m_render_target_textures[RTT_R]);
@@ -320,6 +333,18 @@ RTT::RTT(unsigned int width, unsigned int height, float rtt_scale,
     glBindFramebuffer(GL_FRAMEBUFFER, irr_driver->getDefaultFramebuffer());
 }
 
+#ifdef __EMSCRIPTEN__
+void RTT::copyDepth()
+{
+    FrameBuffer& colors = getFBO(FBO_COLORS);
+    colors.bind();
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, m_depth_copy_fbo);
+    glBlitFramebuffer(0, 0, colors.getWidth(), colors.getHeight(), 0, 0,
+        colors.getWidth(), colors.getHeight(), GL_DEPTH_BUFFER_BIT, GL_NEAREST);
+    colors.bind();
+}
+#endif
+
 RTT::~RTT()
 {
     glBindFramebuffer(GL_FRAMEBUFFER, irr_driver->getDefaultFramebuffer());
@@ -329,6 +354,10 @@ RTT::~RTT()
         delete fb;
     }
     glDeleteTextures(1, &m_depth_stencil_tex);
+#ifdef __EMSCRIPTEN__
+    glDeleteFramebuffers(1, &m_depth_copy_fbo);
+    glDeleteTextures(1, &m_depth_copy_tex);
+#endif
     if (CVS->isShadowEnabled())
     {
         delete m_shadow_fbo;
diff --git a/src/graphics/rtts.hpp b/src/graphics/rtts.hpp
index 709f69ff7..920cfebc7 100644
--- a/src/graphics/rtts.hpp
+++ b/src/graphics/rtts.hpp
@@ -116,6 +116,13 @@ public:
         assert(m_depth_stencil_tex != 0);
         return m_depth_stencil_tex;
     }
+#ifdef __EMSCRIPTEN__
+    /** A copy of the depth taken after the solid objects are drawn, for the
+     *  shaders that read it while the depth is attached to the framebuffer
+     *  (WebGL won't draw like that). */
+    unsigned getDepthCopyTexture() const { return m_depth_copy_tex; }
+    void copyDepth();
+#endif
     unsigned getRenderTarget(enum TypeRTT target) const
     {
         assert(m_render_target_textures[target] != 0);
@@ -131,6 +138,10 @@ private:
     unsigned m_render_target_textures[RTT_COUNT] = {};
     FrameBuffer* m_frame_buffers[FBO_COUNT] = {};
     unsigned m_depth_stencil_tex = 0;
+#ifdef __EMSCRIPTEN__
+    unsigned m_depth_copy_tex = 0;
+    unsigned m_depth_copy_fbo = 0;
+#endif
 
     unsigned int m_width;
     unsigned int m_height;
diff --git a/src/graphics/shader_based_renderer.cpp b/src/graphics/shader_based_renderer.cpp
index 6c0f0ec89..eeb193ecd 100644
--- a/src/graphics/shader_based_renderer.cpp
+++ b/src/graphics/shader_based_renderer.cpp
@@ -349,6 +349,12 @@ void ShaderBasedRenderer::renderSceneDeferred(scene::ICameraSceneNode * const ca
                 irr_driver->getClearColor().getAlpha() / 255.0f;
         }
 
+#ifdef __EMSCRIPTEN__
+        // It reads the depth texture, and WebGL won't draw while it is also
+        // attached.
+        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT,
+            GL_TEXTURE_2D, 0, 0);
+#endif
         CombineDiffuseColor::getInstance()->render(
             m_rtts->getRenderTarget(RTT_DIFFUSE),
             m_rtts->getRenderTarget(RTT_SPECULAR),
@@ -357,9 +363,18 @@ void ShaderBasedRenderer::renderSceneDeferred(scene::ICameraSceneNode * const ca
             m_rtts->getDepthStencilTexture(),
             m_rtts->getRenderTarget(RTT_HALF1), !m_skybox ?
             bg_color : std::array<float, 4>{{0.0f, 0.0f, 0.0f, 0.0f}});
+#ifdef __EMSCRIPTEN__
+        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT,
+            GL_TEXTURE_2D, m_rtts->getDepthStencilTexture(), 0);
+#endif
         PROFILER_POP_CPU_MARKER();
     }
 
+#ifdef __EMSCRIPTEN__
+    // The particles and the displacement read the depth below.
+    m_rtts->copyDepth();
+#endif
+
     if (SP::sp_debug_view)
     {
         glEnable(GL_DEPTH_TEST);
diff --git a/src/graphics/sp/sp_base.cpp b/src/graphics/sp/sp_base.cpp
index 18970f923..e704230b9 100644
--- a/src/graphics/sp/sp_base.cpp
+++ b/src/graphics/sp/sp_base.cpp
@@ -62,6 +62,12 @@
 
 #include <IrrlichtDevice.h>
 
+#ifdef __EMSCRIPTEN__
+// WebGL maps buffers by copying, and only takes write + invalidate.
+#undef GL_MAP_UNSYNCHRONIZED_BIT
+#define GL_MAP_UNSYNCHRONIZED_BIT 0
+#endif
+
 using namespace GE;
 
 namespace SP
@@ -181,7 +187,11 @@ void displaceShaderInit(SPShader* shader)
     shader->addCustomPrefilledTextures(ST_SHADOW,
         GL_TEXTURE_2D, "u_depth", []()->GLuint
         {
+#ifdef __EMSCRIPTEN__
+            return g_stk_sbr->getRTTs()->getDepthCopyTexture();
+#else
             return g_stk_sbr->getRTTs()->getDepthStencilTexture();
+#endif
         }, RP_1ST);
     shader->addCustomPrefilledTextures(ST_TRILINEAR_CLAMPED,
         GL_TEXTURE_CUBE_MAP, "u_skybox_texture", []()->GLuint
diff --git a/src/graphics/sp/sp_mesh_buffer.cpp b/src/graphics/sp/sp_mesh_buffer.cpp
index 25050b5aa..773a2470a 100644
--- a/src/graphics/sp/sp_mesh_buffer.cpp
+++ b/src/graphics/sp/sp_mesh_buffer.cpp
@@ -30,6 +30,12 @@
 #include <set>
 #ifndef SERVER_ONLY
 #include <ge_main.hpp>
+
+#ifdef __EMSCRIPTEN__
+// WebGL maps buffers by copying, and only takes write + invalidate.
+#undef GL_MAP_UNSYNCHRONIZED_BIT
+#define GL_MAP_UNSYNCHRONIZED_BIT 0
+#endif
 #endif
 
 namespace SP
diff --git a/src/graphics/sp/sp_texture_manager.cpp b/src/graphics/sp/sp_texture_manager.cpp
index 5e1e822fb..1519f651c 100644
--- a/src/graphics/sp/sp_texture_manager.cpp
+++ b/src/graphics/sp/sp_texture_manager.cpp
@@ -43,6 +43,9 @@ SPTextureManager::SPTextureManager()
         m_max_threaded_load_obj.store(2);
     }
     m_max_threaded_load_obj.store(m_max_threaded_load_obj.load() + 1);
+#ifdef __EMSCRIPTEN__
+    m_max_threaded_load_obj.store(0);
+#endif
     for (unsigned i = 0; i < m_max_threaded_load_obj; i++)
     {
         m_threaded_load_obj.emplace_back(
@@ -93,6 +96,15 @@ SPTextureManager::~SPTextureManager()
 // ----------------------------------------------------------------------------
 void SPTextureManager::checkForGLCommand(bool before_scene)
 {
+#ifdef __EMSCRIPTEN__
+    std::list<std::function<bool()> > waiting;
+    waiting.swap(m_threaded_functions);
+    for (auto& f : waiting)
+    {
+        if (!f())
+            m_threaded_functions.push_back(f);
+    }
+#endif
     if (m_gl_cmd_function_count.load() == 0)
     {
         return;
diff --git a/src/graphics/sp/sp_texture_manager.hpp b/src/graphics/sp/sp_texture_manager.hpp
index 685803fe5..0ec41c707 100644
--- a/src/graphics/sp/sp_texture_manager.hpp
+++ b/src/graphics/sp/sp_texture_manager.hpp
@@ -103,6 +103,13 @@ public:
     // ------------------------------------------------------------------------
     void addThreadedFunction(std::function<bool()> threaded_function)
     {
+#ifdef __EMSCRIPTEN__
+        // No threads on the web: run it now, and again with the GL commands
+        // if it has to wait.
+        if (!threaded_function())
+            m_threaded_functions.push_back(threaded_function);
+        return;
+#endif
         std::lock_guard<std::mutex> lock(m_thread_obj_mutex);
         m_threaded_functions.push_back(threaded_function);
         m_thread_obj_cv.notify_one();
diff --git a/src/input/input_manager.cpp b/src/input/input_manager.cpp
index 99cff967f..fc57a7d0c 100644
--- a/src/input/input_manager.cpp
+++ b/src/input/input_manager.cpp
@@ -124,11 +124,13 @@ InputManager::InputManager() : m_mode(BOOTSTRAP),
             SDL_GetError());
     }
 
+#ifndef __EMSCRIPTEN__
     if (SDL_InitSubSystem(SDL_INIT_HAPTIC) != 0)
     {
         Log::error("InputManager", "Failed to init SDL haptics: %s",
             SDL_GetError());
     }
+#endif
 #endif // SERVER_ONLY
 }
 
diff --git a/src/io/file_manager.cpp b/src/io/file_manager.cpp
index ece404d23..c32ac869d 100644
--- a/src/io/file_manager.cpp
+++ b/src/io/file_manager.cpp
@@ -213,6 +213,10 @@ FileManager::FileManager()
 #endif
     }
 
+#ifdef __EMSCRIPTEN__
+    root_dir = "/data/";
+#endif
+
     if (!m_file_system->existFile((root_dir + version).c_str()))
     {
         Log::error("FileManager", "Could not find file '%s'in any "
diff --git a/src/karts/controller/local_player_controller.cpp b/src/karts/controller/local_player_controller.cpp
index cc0bda814..b1580f030 100644
--- a/src/karts/controller/local_player_controller.cpp
+++ b/src/karts/controller/local_player_controller.cpp
@@ -490,7 +490,7 @@ void LocalPlayerController::doCrashHaptics() {
 }
 
 void LocalPlayerController::rumble(float strength_low, float strength_high, uint16_t duration) {
-#ifndef SERVER_ONLY
+#if !defined(SERVER_ONLY) && !defined(__EMSCRIPTEN__)
     if (RewindManager::get()->isRewinding())
         return;
     int count = input_manager->getGamepadCount();
diff --git a/src/main.cpp b/src/main.cpp
index 5bd197976..aa0319179 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -166,6 +166,22 @@
 #include <jni.h>
 #endif
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#endif
+
+#ifdef __EMSCRIPTEN__
+#include <SDL.h>
+// Called by the web page when the space for the game changes size: SDL then
+// reports a resize, as a desktop window would.
+extern "C" EMSCRIPTEN_KEEPALIVE void wg_resize(int width, int height)
+{
+    SDL_Window* window = SDL_GL_GetCurrentWindow();
+    if (window)
+        SDL_SetWindowSize(window, width, height);
+}
+#endif
+
 #ifdef __SWITCH__
 extern "C" {
   #include <sys/iosupport.h>
@@ -2040,6 +2056,12 @@ void initRest()
 //=============================================================================
 void askForInternetPermission()
 {
+#ifdef __EMSCRIPTEN__
+    // The web build has no threads for downloads, so it stays offline.
+    UserConfigParams::m_internet_status =
+        Online::RequestManager::IPERM_NOT_ALLOWED;
+    return;
+#endif
     if (UserConfigParams::m_internet_status !=
         Online::RequestManager::IPERM_NOT_ASKED)
         return;
@@ -2146,7 +2168,23 @@ void debugLoop()
 }
 #endif
 
+#ifdef __EMSCRIPTEN__
+// Called by the web page before it reads the save: writes best times,
+// progress, achievements and settings now, as a page never runs the
+// destructors that write them on the desktop.
+extern "C" EMSCRIPTEN_KEEPALIVE void wg_save()
+{
+    if (highscore_manager)
+        highscore_manager->saveHighscores();
+    if (PlayerManager::get())
+        PlayerManager::get()->save();
+    if (user_config)
+        user_config->saveConfig();
+}
+#endif
+
 // ----------------------------------------------------------------------------
+void endMainLoop();
 #if defined(ANDROID)
 int android_main(int argc, char *argv[])
 #elif defined(IOS_STK)
@@ -2155,6 +2193,10 @@ int ios_main(int argc, char *argv[])
 int main(int argc, char *argv[])
 #endif
 {
+#ifdef __EMSCRIPTEN__
+    // The name of the player made on the first visit (Emscripten's is "web_user").
+    setenv("USER", "Player", 1);
+#endif
 #ifdef __SWITCH__
     constexpr devoptab_t dotab_stdout = {
         .name    = "con",
@@ -2491,7 +2533,7 @@ int main(int argc, char *argv[])
             }
             else if (!CVS->isGLSL() && irr_driver->getVideoDriver()->getDriverType() != video::EDT_VULKAN)
             {
-                #if !defined(MOBILE_STK)
+                #if !defined(MOBILE_STK) && !defined(__EMSCRIPTEN__)
                 if (UserConfigParams::m_old_driver_popup)
                 {
                     #ifdef USE_GLES2
@@ -2533,6 +2575,10 @@ int main(int argc, char *argv[])
             {
                 PlayerManager::get()->enforceCurrentPlayer();
             }
+#ifdef __EMSCRIPTEN__
+            // Online accounts can't be used here: play as the local player.
+            PlayerManager::get()->enforceCurrentPlayer();
+#endif
 
             // If there is a current player, it was saved in the config file,
             // so we immediately start the main menu (unless it was requested
@@ -2626,8 +2672,19 @@ int main(int argc, char *argv[])
         // Game loaded, bring CPU / GPU clock back to normal
         appletSetCpuBoostMode(ApmCpuBoostMode_Normal);
 #endif
-
+#ifdef __EMSCRIPTEN__
+        auto mainLoopWrapper = []() {
+            main_loop->run();
+            if (main_loop->isAborted()) {
+                endMainLoop();
+                emscripten_cancel_main_loop();
+                exit(0);
+            }
+        };
+        emscripten_set_main_loop(mainLoopWrapper, 0, 1);
+#else
         main_loop->run();
+#endif
 
     }  // try
     catch (std::exception &e)
@@ -2639,6 +2696,18 @@ int main(int argc, char *argv[])
     }
 
     /* Program closing...*/
+    endMainLoop();
+
+#ifdef IOS_STK
+    // App store may not like this, but this can happen if player uses keyboard to quit stk
+    exit(0);
+    return 0;
+#else
+    return 0 ;
+#endif
+}   // main
+
+void endMainLoop() {
 
 #ifdef ENABLE_WIIUSE
     if(wiimote_manager)
@@ -2690,15 +2759,7 @@ int main(int argc, char *argv[])
     socketExit();
     nifmExit();
 #endif
-
-#ifdef IOS_STK
-    // App store may not like this, but this can happen if player uses keyboard to quit stk
-    exit(0);
-    return 0;
-#else
-    return 0 ;
-#endif
-}   // main
+}
 
 // ============================================================================
 #ifdef WIN32
diff --git a/src/main_loop.cpp b/src/main_loop.cpp
index 8a06c869b..3d70284fe 100644
--- a/src/main_loop.cpp
+++ b/src/main_loop.cpp
@@ -84,6 +84,7 @@ extern "C" {
 #endif
 
 MainLoop* main_loop = 0;
+double left_over_time = 0;
 
 #ifdef WIN32
 LRESULT CALLBACK separateProcessProc(_In_ HWND hwnd, _In_ UINT uMsg, 
@@ -399,11 +400,12 @@ void MainLoop::updateRace(int ticks, bool fast_forward)
  */
 void MainLoop::run()
 {
+#ifndef __EMSCRIPTEN__
     m_curr_time = std::chrono::steady_clock::now();
+#endif
     // DT keeps track of the leftover time, since the race update
     // happens in fixed timesteps
-    double left_over_time = 0;
-
+    
 #ifdef WIN32
     HANDLE parent = 0;
     if (m_parent_pid != 0)
@@ -417,8 +419,14 @@ void MainLoop::run()
     }
 #endif
 
+#ifndef __EMSCRIPTEN__
     while (!m_abort)
+#endif
+
     {
+#ifdef __EMSCRIPTEN__
+        RaceManager::get()->wgPoll();
+#endif
 #ifdef __SWITCH__
       // This feeds us messages (like when the Switch sleeps or requests an exit)
       m_abort = !appletMainLoop();
@@ -708,6 +716,7 @@ void MainLoop::run()
             }
         }
 
+#ifndef __EMSCRIPTEN__
         if (!UserConfigParams::m_benchmark)
         {
             TimePoint frame_end = std::chrono::steady_clock::now();
@@ -734,6 +743,7 @@ void MainLoop::run()
                 PROFILER_POP_CPU_MARKER();
             }
         }
+#endif
 
         PROFILER_POP_CPU_MARKER();   // MainLoop pop
         PROFILER_SYNC_FRAME();
diff --git a/src/online/request_manager.cpp b/src/online/request_manager.cpp
index 0c39bce3e..6450b5167 100644
--- a/src/online/request_manager.cpp
+++ b/src/online/request_manager.cpp
@@ -82,7 +82,8 @@ namespace Online
     // ------------------------------------------------------------------------
     RequestManager::~RequestManager()
     {
-        m_thread.join();
+        if (m_thread.joinable())
+            m_thread.join();
         Online::globalHTTPRequestCleanup();
     }   // ~RequestManager
 
@@ -98,7 +99,10 @@ namespace Online
      */
     void RequestManager::startNetworkThread()
     {
+#ifndef __EMSCRIPTEN__
+        // The web build has no threads and stays offline.
         m_thread = std::thread(std::bind(mainLoop, this));
+#endif
         // In case that login id was not saved (or first start of stk),
         // current player would not be defined at this stage.
         PlayerProfile *player = PlayerManager::getCurrentPlayer();
diff --git a/src/race/race_manager.cpp b/src/race/race_manager.cpp
index f58d51985..8fb94ae56 100644
--- a/src/race/race_manager.cpp
+++ b/src/race/race_manager.cpp
@@ -69,6 +69,28 @@
 
 #include <IrrlichtDevice.h>
 
+#ifdef __EMSCRIPTEN__
+#include "guiengine/modaldialog.hpp"
+#include "guiengine/widgets/icon_button_widget.hpp"
+#include "states_screens/dialogs/message_dialog.hpp"
+#include "states_screens/main_menu_screen.hpp"
+#include <emscripten.h>
+// The web page downloads each track's models and textures while the game
+// runs; it answers whether a track's files are in yet (and fetches that one
+// next if not).
+EM_JS(int, wg_track_ready, (const char* track), {
+    return Module.wgTrackReady ? Module.wgTrackReady(UTF8ToString(track)) : 1;
+});
+static bool g_wg_waiting_for_track = false;
+// The message shown while a race waits: its button (or Esc) stops waiting.
+class WgTrackWait : public MessageDialog::IConfirmDialogListener
+{
+public:
+    ~WgTrackWait() { g_wg_waiting_for_track = false; }
+    virtual void onConfirm() OVERRIDE { GUIEngine::ModalDialog::dismiss(); }
+};
+#endif
+
 #ifdef __SWITCH__
 extern "C" {
   #define u64 uint64_t
@@ -546,6 +568,27 @@ void RaceManager::startNew(bool from_overworld)
  */
 void RaceManager::startNextRace()
 {
+#ifdef __EMSCRIPTEN__
+    // A track still downloading: the game goes back to the menus (the caller
+    // left the game state, with no world yet) and shows a message, and the
+    // race starts from wgPoll() once the track is in.
+    if (m_track_number < (int)m_tracks.size() &&
+        !wg_track_ready(m_tracks[m_track_number].c_str()))
+    {
+        if (GUIEngine::ModalDialog::isADialogActive())
+            GUIEngine::ModalDialog::dismiss();
+        StateManager::get()->resetAndGoToScreen(MainMenuScreen::getInstance());
+        MessageDialog* wait = new MessageDialog(
+            L"Downloading this track, the race starts as soon as it's in.",
+            MessageDialog::MESSAGE_DIALOG_OK, new WgTrackWait(), true);
+        GUIEngine::IconButtonWidget* cancel =
+            wait->getWidget<GUIEngine::IconButtonWidget>("confirm");
+        cancel->setImage("gui/icons/red_x.png");
+        cancel->setLabel(_("Cancel"));
+        g_wg_waiting_for_track = true;
+        return;
+    }
+#endif
 #ifdef __SWITCH__
     // Throttles GPU while boosting CPU
     appletSetCpuBoostMode(ApmCpuBoostMode_FastLoad);
@@ -1344,4 +1387,20 @@ void RaceManager::setBenchmarking(bool benchmark)
 void RaceManager::scheduleBenchmark()
 {
     m_scheduled_benchmark = true;
-}   // scheduleBenchmark
\ No newline at end of file
+}   // scheduleBenchmark
+#ifdef __EMSCRIPTEN__
+// ----------------------------------------------------------------------------
+/** Called every frame: starts the race that waited for its track. */
+void RaceManager::wgPoll()
+{
+    if (!g_wg_waiting_for_track || m_track_number >= (int)m_tracks.size() ||
+        !wg_track_ready(m_tracks[m_track_number].c_str()))
+        return;
+    // Closing the message clears the flag.
+    if (GUIEngine::ModalDialog::isADialogActive())
+        GUIEngine::ModalDialog::dismiss();
+    g_wg_waiting_for_track = false;
+    StateManager::get()->enterGameState();
+    startNextRace();
+}   // wgPoll
+#endif
diff --git a/src/race/race_manager.hpp b/src/race/race_manager.hpp
index e93078ccc..3ade9e4ac 100644
--- a/src/race/race_manager.hpp
+++ b/src/race/race_manager.hpp
@@ -247,6 +247,9 @@ private:
     bool m_started_from_overworld;
 
 public:
+#ifdef __EMSCRIPTEN__
+    void wgPoll();
+#endif
 
     /** This data structure accumulates kart data and race result data from
      *  each race. */
diff --git a/src/states_screens/main_menu_screen.cpp b/src/states_screens/main_menu_screen.cpp
index ccd4a4613..22dd14ddc 100644
--- a/src/states_screens/main_menu_screen.cpp
+++ b/src/states_screens/main_menu_screen.cpp
@@ -117,6 +117,15 @@ void MainMenuScreen::loadedFromFile()
 
 void MainMenuScreen::beforeAddingWidget()
 {
+#ifdef __EMSCRIPTEN__
+    // The web build is offline, and quitting would leave a dead page.
+    for (const char* id : { "online", "addons", "quit" })
+    {
+        Widget* w = getWidget(id);
+        if (w)
+            w->setVisible(false);
+    }
+#endif
 #ifdef IOS_STK
     // iOS app doesn't like quit button in UI
     Widget* w = getWidget("quit");
@@ -704,6 +713,10 @@ void MainMenuScreen::onDisabledItemClicked(const std::string& item)
 
 bool MainMenuScreen::onEscapePressed()
 {
+#ifdef __EMSCRIPTEN__
+    // A web page can't quit.
+    return false;
+#endif
     class ConfirmClose :
           public MessageDialog::IConfirmDialogListener
     {
diff --git a/src/states_screens/options/options_screen_display.cpp b/src/states_screens/options/options_screen_display.cpp
index db4504112..ac81eaea6 100644
--- a/src/states_screens/options/options_screen_display.cpp
+++ b/src/states_screens/options/options_screen_display.cpp
@@ -135,13 +135,18 @@ void OptionsScreenDisplay::init()
     full->setActive(!in_game || is_vulkan_fullscreen_desktop);
     applyBtn->setActive(!in_game);
 
-#if defined(MOBILE_STK) || defined(__SWITCH__)
+#if defined(MOBILE_STK) || defined(__SWITCH__) || defined(__EMSCRIPTEN__)
     applyBtn->setVisible(false);
     full->setVisible(false);
     getWidget<LabelWidget>("fullscreenText")->setVisible(false);
     rememberWinpos->setVisible(false);
     getWidget<LabelWidget>("rememberWinposText")->setVisible(false);
 #endif
+#ifdef __EMSCRIPTEN__
+    // The web page sizes the game and owns full screen.
+    res->setVisible(false);
+    getWidget<LabelWidget>("resolutionText")->setVisible(false);
+#endif
 
     updateResolutionsList();
 
diff --git a/src/states_screens/options/options_screen_general.cpp b/src/states_screens/options/options_screen_general.cpp
index b83e7c4b1..dfee6a1f0 100644
--- a/src/states_screens/options/options_screen_general.cpp
+++ b/src/states_screens/options/options_screen_general.cpp
@@ -54,6 +54,10 @@ void OptionsScreenGeneral::init()
     assert(ribbon != NULL);
     ribbon->setFocusForPlayer(PLAYER_ID_GAME_MASTER);
     ribbon->select( "tab_general", PLAYER_ID_GAME_MASTER );
+#ifdef __EMSCRIPTEN__
+    // The web build has no online play.
+    getWidget("internet_box")->setVisible(false);
+#endif
 
     CheckBoxWidget* internet_enabled = getWidget<CheckBoxWidget>("enable-internet");
     assert( internet_enabled != NULL );
diff --git a/src/states_screens/options/user_screen.cpp b/src/states_screens/options/user_screen.cpp
index a260fcb3a..9e918657b 100644
--- a/src/states_screens/options/user_screen.cpp
+++ b/src/states_screens/options/user_screen.cpp
@@ -279,6 +279,14 @@ void BaseUserScreen::makeEntryFieldsVisible()
     getWidget<CheckBoxWidget>("guest")->setVisible(online);
 #endif
     bool online = m_online_cb->getState();
+#ifdef __EMSCRIPTEN__
+    // The web build has no online play.
+    online = false;
+    m_online_cb->setState(false);
+    m_online_cb->setVisible(false);
+    if (Widget* label = getWidget("label_online"))
+        label->setVisible(false);
+#endif
     getWidget<LabelWidget>("label_username")->setVisible(online);
     m_username_tb->setVisible(online);
     getWidget<LabelWidget>("label_remember")->setVisible(online);