diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1655cee..3b8ec2e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -140,6 +140,7 @@ if (NOT EMSCRIPTEN)
 else (EMSCRIPTEN)
   add_executable(binjgb
     src/memory.c
+    src/common.c
     src/emulator.c
     src/joypad.c
     src/rewind.c
diff --git a/src/common.c b/src/common.c
index 457ba8d..52f3b0c 100644
--- a/src/common.c
+++ b/src/common.c
@@ -33,6 +33,7 @@ static Result get_file_size(FILE* f, long* out_size) {
   ON_ERROR_RETURN;
 }
 
+#ifndef __wasm__
 Result file_read(const char* filename, FileData* out_file_data) {
   return file_read_aligned(filename, 1, out_file_data);
 }
@@ -63,6 +64,16 @@ Result file_write(const char* filename, const FileData* file_data) {
   return OK;
   ON_ERROR_CLOSE_FILE_AND_RETURN;
 }
+#endif
+
+void file_data_resize(FileData* file_data, size_t new_size) {
+  size_t old_size = file_data->size;
+  file_data->data = xrealloc(file_data->data, new_size);
+  if (new_size > old_size) {
+    memset(file_data->data + old_size, 0, new_size - old_size);
+  }
+  file_data->size = new_size;
+}
 
 void file_data_delete(FileData* file_data) {
   xfree(file_data->data);
diff --git a/src/common.h b/src/common.h
index dbd522e..9513ba9 100644
--- a/src/common.h
+++ b/src/common.h
@@ -108,9 +108,12 @@ typedef struct JoypadButtons {
 } JoypadButtons;
 
 const char* replace_extension(const char* filename, const char* extension);
+#ifndef __wasm__
 Result file_read(const char* filename, FileData* out);
 Result file_read_aligned(const char* filename, size_t align, FileData* out);
 Result file_write(const char* filename, const FileData*);
+#endif
+void file_data_resize(FileData*, size_t new_size);
 void file_data_delete(FileData*);
 
 #ifdef __cplusplus
diff --git a/src/emscripten/wrapper.c b/src/emscripten/wrapper.c
index a0b3271..6ffc9e7 100644
--- a/src/emscripten/wrapper.c
+++ b/src/emscripten/wrapper.c
@@ -185,11 +185,6 @@ size_t get_file_data_size(FileData* file_data) {
   return file_data->size;
 }
 
-void file_data_delete(FileData* file_data) {
-  xfree(file_data->data);
-  xfree(file_data);
-}
-
 void set_log_apu_writes(Emulator* e, Bool set) {
   s_config.log_apu_writes = set;
   emulator_set_config(e, &s_config);
diff --git a/src/emulator.c b/src/emulator.c
index 215b13d..7985bb7 100644
--- a/src/emulator.c
+++ b/src/emulator.c
@@ -1120,7 +1120,8 @@ static void set_cart_info(Emulator* e, u8 index) {
 }
 
 static Result get_cart_info(FileData* file_data, size_t offset,
-                            CartInfo* cart_info, Bool require_logo_checksum) {
+                            CartInfo* cart_info, Bool require_logo_checksum,
+                            size_t* max_file_size) {
   /* Simple checksum on logo data so we don't have to include it here. :) */
   u8* data = file_data->data + offset;
   size_t i;
@@ -1159,38 +1160,46 @@ static Result get_cart_info(FileData* file_data, size_t offset,
   }
 
   u32 rom_byte_size = s_rom_bank_count[cart_info->rom_size] << ROM_BANK_SHIFT;
-  cart_info->size = rom_byte_size;
-  CHECK_MSG(file_data->size >= offset + rom_byte_size,
-            "File size too small (required %ld, got %ld)\n",
-            (long)(offset + rom_byte_size), (long)file_data->size);
+  *max_file_size = MAX(*max_file_size, offset + rom_byte_size);
 
   return OK;
   ON_ERROR_RETURN;
 }
 
 static Result get_cart_infos(Emulator* e) {
+  size_t file_size = e->file_data.size;
+  size_t max_file_size = file_size;
   u32 i;
   for (i = 0; i < MAX_CART_INFOS; ++i) {
     size_t offset = i << CART_INFO_SHIFT;
     if (offset + MINIMUM_ROM_SIZE > e->file_data.size) break;
-    if (SUCCESS(
-            get_cart_info(&e->file_data, offset, &e->cart_infos[i], TRUE))) {
+    if (SUCCESS(get_cart_info(&e->file_data, offset, &e->cart_infos[i], TRUE,
+                              &max_file_size))) {
       if (s_cart_type_info[e->cart_infos[i].cart_type].mbc_type ==
           MBC_TYPE_MMM01) {
         /* MMM01 has the cart header at the end. */
-        set_cart_info(e, i);
-        return OK;
+        goto done;
       }
       e->cart_info_count++;
     }
   }
   // Maybe the logo checksum failed; try again without it required.
   if (e->cart_info_count == 0 &&
-      SUCCESS(get_cart_info(&e->file_data, 0, &e->cart_infos[0], FALSE))) {
+      SUCCESS(get_cart_info(&e->file_data, 0, &e->cart_infos[0], FALSE,
+                            &max_file_size))) {
     e->cart_info_count++;
   }
   CHECK_MSG(e->cart_info_count != 0, "Invalid ROM.\n");
-  set_cart_info(e, 0);
+  i = 0;
+done:
+  if (max_file_size > file_size) {
+    file_data_resize(&e->file_data, max_file_size);
+    // Fix cart_info data pointers.
+    for (u32 j = 0; j < e->cart_info_count; ++j) {
+      e->cart_infos[j].data = e->file_data.data + e->cart_infos[j].offset;
+    }
+  }
+  set_cart_info(e, i);
   return OK;
   ON_ERROR_RETURN;
 }
@@ -4970,6 +4979,7 @@ Result emulator_write_ext_ram(Emulator* e, FileData* file_data) {
   ON_ERROR_RETURN;
 }
 
+#ifndef __wasm__
 Result emulator_read_ext_ram_from_file(Emulator* e, const char* filename) {
   if (EXT_RAM.battery_type != BATTERY_TYPE_WITH_BATTERY)
     return OK;
@@ -5023,6 +5033,7 @@ Result emulator_write_state_to_file(Emulator* e, const char* filename) {
   file_data_delete(&file_data);
   return result;
 }
+#endif
 
 Emulator* emulator_new(const EmulatorInit* init) {
   Emulator* e = xcalloc(1, sizeof(Emulator));
@@ -5039,6 +5050,7 @@ Emulator* emulator_new(const EmulatorInit* init) {
 void emulator_delete(Emulator* e) {
   if (e) {
     xfree(e->audio_buffer.data);
+    file_data_delete(&e->file_data);
     xfree(e);
   }
 }
diff --git a/src/emulator.h b/src/emulator.h
index e624499..6d40ed4 100644
--- a/src/emulator.h
+++ b/src/emulator.h
@@ -231,10 +231,12 @@ Result emulator_write_state(Emulator*, FileData*);
 Result emulator_read_ext_ram(Emulator*, const FileData*);
 Result emulator_write_ext_ram(Emulator*, FileData*);
 
+#ifndef __wasm__
 Result emulator_read_state_from_file(Emulator*, const char* filename);
 Result emulator_write_state_to_file(Emulator*, const char* filename);
 Result emulator_read_ext_ram_from_file(Emulator*, const char* filename);
 Result emulator_write_ext_ram_to_file(Emulator*, const char* filename);
+#endif
 
 EmulatorEvent emulator_step(Emulator*);
 EmulatorEvent emulator_run_until(Emulator*, Ticks until_ticks);
diff --git a/src/memory.c b/src/memory.c
index c19f865..ef3d6d4 100644
--- a/src/memory.c
+++ b/src/memory.c
@@ -20,6 +20,13 @@ void* xmalloc_(const char* file, int line, size_t size) {
   return p;
 }
 
+void* xrealloc_(const char* file, int line, void* p, size_t size) {
+  void* newp = realloc(size);
+  printf("%s:%d: %s(%p, %" PRIu64 ") => %p\n", file, line, __func__, p,
+         (uint64_t)size, newp);
+  return newp;
+}
+
 void xfree_(const char* file, int line, void* p) {
   printf("%s:%d: %s(%p)\n", file, line, __func__, p);
   free(p);
diff --git a/src/memory.h b/src/memory.h
index a62c5ed..7a0357b 100644
--- a/src/memory.h
+++ b/src/memory.h
@@ -19,12 +19,14 @@ extern "C" {
 #if TRACE_MEMORY
 
 #define xmalloc(size) xmalloc_(__FILE__, __LINE__, size)
+#define xrealloc(size) xrealloc_(__FILE__, __LINE__, p, size)
 #define xfree(p) xfree_(__FILE__, __LINE__, p)
 #define xcalloc(count, size) xcalloc_(__FILE__, __LINE__, count, size)
 #define xstrdup(s) xstrdup_(__FILE__, __LINE__, s)
 
 /* Use these instead to make it easier to track memory usage. */
 void* xmalloc_(const char* file, int line, size_t);
+void* xrealloc_(const char* file, int line, void*, size_t);
 void xfree_(const char* file, int line, void*);
 void* xcalloc_(const char* file, int line, size_t, size_t);
 char* xstrdup_(const char* file, int line, const char*);
@@ -32,6 +34,7 @@ char* xstrdup_(const char* file, int line, const char*);
 #else
 
 #define xmalloc malloc
+#define xrealloc realloc
 #define xfree free
 #define xcalloc calloc
 #define xstrdup strdup