diff --git a/backends/meson.build b/backends/meson.build
index da714b93d1..9b88d22685 100644
--- a/backends/meson.build
+++ b/backends/meson.build
@@ -12,8 +12,10 @@ system_ss.add([files(
 
 if host_os != 'windows'
   system_ss.add(files('rng-random.c'))
-  system_ss.add(files('hostmem-file.c'))
-  system_ss.add([files('hostmem-shm.c'), rt])
+  if host_os != 'emscripten'
+    system_ss.add(files('hostmem-file.c'))
+    system_ss.add([files('hostmem-shm.c'), rt])
+  endif
 endif
 if host_os == 'linux'
   system_ss.add(files('hostmem-memfd.c'))
diff --git a/system/memory.c b/system/memory.c
index 85f6834cb3..3958314765 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -1636,7 +1636,7 @@ bool memory_region_init_resizeable_ram(MemoryRegion *mr,
     return true;
 }
 
-#ifdef CONFIG_POSIX
+#if defined(CONFIG_POSIX) && !defined(EMSCRIPTEN)
 bool memory_region_init_ram_from_file(MemoryRegion *mr,
                                       Object *owner,
                                       const char *name,
diff --git a/system/physmem.c b/system/physmem.c
index 75389064a8..addd5d0c4b 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -1235,7 +1235,7 @@ long qemu_maxrampagesize(void)
     return pagesize;
 }
 
-#ifdef CONFIG_POSIX
+#if defined(CONFIG_POSIX) && !defined(EMSCRIPTEN)
 static int64_t get_file_size(int fd)
 {
     int64_t size;
@@ -1941,7 +1941,7 @@ out_free:
     }
 }
 
-#ifdef CONFIG_POSIX
+#if defined(CONFIG_POSIX) && !defined(EMSCRIPTEN)
 RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
                                  uint32_t ram_flags, int fd, off_t offset,
                                  Error **errp)
@@ -2130,7 +2130,7 @@ static void reclaim_ramblock(RAMBlock *block)
         ;
     } else if (xen_enabled()) {
         xen_invalidate_map_cache_entry(block->host);
-#ifndef _WIN32
+#if !defined(_WIN32) && !defined(EMSCRIPTEN)
     } else if (block->fd >= 0) {
         qemu_ram_munmap(block->fd, block->host, block->max_length);
         close(block->fd);
diff --git a/util/meson.build b/util/meson.build
index 5d8bef9891..e107fbfb69 100644
--- a/util/meson.build
+++ b/util/meson.build
@@ -11,7 +11,9 @@ if host_os != 'windows'
   endif
   util_ss.add(files('compatfd.c'))
   util_ss.add(files('event_notifier-posix.c'))
-  util_ss.add(files('mmap-alloc.c'))
+  if host_os != 'emscripten'
+    util_ss.add(files('mmap-alloc.c'))
+  endif
   freebsd_dep = []
   if host_os == 'freebsd'
     freebsd_dep = util
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 11b35e48fb..760c3d4f4c 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -58,6 +58,7 @@
 #include <lwp.h>
 #endif
 
+#include "qemu/memalign.h"
 #include "qemu/mmap-alloc.h"
 
 #define MAX_MEM_PREALLOC_THREAD_COUNT 16
@@ -192,14 +193,18 @@ fail_close:
 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared,
                           bool noreserve)
 {
+    size_t align = QEMU_VMALLOC_ALIGN;
+#ifndef EMSCRIPTEN
     const uint32_t qemu_map_flags = (shared ? QEMU_MAP_SHARED : 0) |
                                     (noreserve ? QEMU_MAP_NORESERVE : 0);
-    size_t align = QEMU_VMALLOC_ALIGN;
     void *ptr = qemu_ram_mmap(-1, size, align, qemu_map_flags, 0);
 
     if (ptr == MAP_FAILED) {
         return NULL;
     }
+#else
+    void *ptr = qemu_memalign(align, size);
+#endif
 
     if (alignment) {
         *alignment = align;
@@ -212,7 +217,11 @@ void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared,
 void qemu_anon_ram_free(void *ptr, size_t size)
 {
     trace_qemu_anon_ram_free(ptr, size);
+#ifndef EMSCRIPTEN
     qemu_ram_munmap(-1, ptr, size);
+#else
+    qemu_vfree(ptr);
+#endif
 }
 
 void qemu_socket_set_block(int fd)
@@ -573,7 +582,11 @@ bool qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
 {
     static gsize initialized;
     int ret;
+#ifndef EMSCRIPTEN
     size_t hpagesize = qemu_fd_getpagesize(fd);
+#else
+    size_t hpagesize = qemu_real_host_page_size();
+#endif
     size_t numpages = DIV_ROUND_UP(sz, hpagesize);
     bool use_madv_populate_write;
     struct sigaction act;