diff --git a/emscripten.py b/emscripten.py
index 47a825d87..e689cc699 100755
--- a/emscripten.py
+++ b/emscripten.py
@@ -168,6 +168,7 @@ def main(args):
   settings = {}
   for setting in args.settings:
     name, value = setting.strip().split('=', 1)
+    assert name != 'OPTIMIZE', 'OPTIMIZE has been renamed MICRO_OPTS, to not confuse new users. Sorry for any inconvenience.'
     settings[name] = json.loads(value)
 
   # Adjust sign correction for dlmalloc.
diff --git a/src/analyzer.js b/src/analyzer.js
index efba03e8b..52017f276 100644
--- a/src/analyzer.js
+++ b/src/analyzer.js
@@ -363,10 +363,10 @@ function analyzer(data) {
             variable.impl = VAR_EMULATED;
           } else if (variable.type == 'i64*' && I64_MODE == 1) {
             variable.impl = VAR_EMULATED;
-          } else if (OPTIMIZE && variable.pointingLevels === 0 && !variable.hasAddrTaken) {
+          } else if (MICRO_OPTS && variable.pointingLevels === 0 && !variable.hasAddrTaken) {
             // A simple int value, can be implemented as a native variable
             variable.impl = VAR_NATIVE;
-          } else if (OPTIMIZE && variable.origin === 'alloca' && !variable.hasAddrTaken && !variable.hasValueTaken &&
+          } else if (MICRO_OPTS && variable.origin === 'alloca' && !variable.hasAddrTaken && !variable.hasValueTaken &&
                      variable.allocatedNum === 1 &&
                      (Runtime.isNumberType(pointedType) || Runtime.isPointerType(pointedType))) {
             // A pointer to a value which is only accessible through this pointer. Basically
diff --git a/src/compiler.js b/src/compiler.js
index 3d33ed22f..fd96386c6 100644
--- a/src/compiler.js
+++ b/src/compiler.js
@@ -62,7 +62,7 @@ assert(!(USE_TYPED_ARRAYS === 2 && QUANTUM_SIZE !== 4), 'For USE_TYPED_ARRAYS ==
 
 // Output some info and warnings based on settings
 
-if (!OPTIMIZE || !RELOOP || ASSERTIONS || CHECK_SIGNS || CHECK_OVERFLOWS || INIT_STACK || INIT_HEAP ||
+if (!MICRO_OPTS || !RELOOP || ASSERTIONS || CHECK_SIGNS || CHECK_OVERFLOWS || INIT_STACK || INIT_HEAP ||
     !SKIP_STACK_IN_SMALL || SAFE_HEAP || PGO || PROFILE || !DISABLE_EXCEPTION_CATCHING) {
   print('// Note: Some Emscripten settings will significantly limit the speed of the generated code.');
 } else {
diff --git a/src/settings.js b/src/settings.js
index 1d64f1439..acdb8c149 100644
--- a/src/settings.js
+++ b/src/settings.js
@@ -37,7 +37,7 @@ TOTAL_MEMORY = 50*1024*1024; // The total amount of memory to use. This mainly m
                              // is currently no warning about that!
 
 // Code embetterments
-OPTIMIZE = 0; // Optimize llvm operations into js commands
+MICRO_OPTS = 0; // Various micro-optimizations, like nativizing variables
 RELOOP = 0; // Recreate js native loops from llvm data
 USE_TYPED_ARRAYS = 0; // Try to use typed arrays for the heap
                       // 1 has two heaps, IHEAP (int32) and FHEAP (double),
diff --git a/tests/runner.py b/tests/runner.py
index 2a050deb5..ced640df8 100644
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -1551,7 +1551,7 @@ if 'benchmark' not in str(sys.argv):
         self.do_run(src, '*2,2,5,8,8***8,8,5,8,8***7,2,6,990,7,2*', [], lambda x: x.replace('\n', '*'))
 
     def test_emscripten_api(self):
-        #if Settings.OPTIMIZE or Settings.RELOOP or Building.LLVM_OPTS: return self.skip('FIXME')
+        #if Settings.MICRO_OPTS or Settings.RELOOP or Building.LLVM_OPTS: return self.skip('FIXME')
 
         src = '''
           #include <stdio.h>
@@ -3299,7 +3299,7 @@ if 'benchmark' not in str(sys.argv):
     def test_freetype(self):
       if Settings.QUANTUM_SIZE == 1: return self.skip('TODO: Figure out and try to fix')
 
-      if Building.LLVM_OPTS: Settings.RELOOP = 0 # Too slow; we do care about typed arrays and OPTIMIZE though
+      if Building.LLVM_OPTS: Settings.RELOOP = 0 # Too slow; we do care about typed arrays and MICRO_OPTS though
 
       if Settings.CORRECT_SIGNS == 0: Settings.CORRECT_SIGNS = 1 # Not sure why, but needed
 
@@ -3558,7 +3558,7 @@ if 'benchmark' not in str(sys.argv):
       # Overflows in string_hash
       Settings.CORRECT_OVERFLOWS = 1
       Settings.CHECK_OVERFLOWS = 0
-      Settings.RELOOP = 0 # Too slow; we do care about typed arrays and OPTIMIZE though
+      Settings.RELOOP = 0 # Too slow; we do care about typed arrays and MICRO_OPTS though
       Settings.SAFE_HEAP = 0 # Has bitfields which are false positives. Also the PyFloat_Init tries to detect endianness.
       Settings.CORRECT_SIGNS = 1 # Not sure why, but needed
       Settings.EXPORTED_FUNCTIONS = ['_main', '_PyRun_SimpleStringFlags'] # for the demo
@@ -4397,7 +4397,7 @@ class %s(T):
     quantum_size = %d
     Settings.USE_TYPED_ARRAYS = %d
     Settings.INVOKE_RUN = 1
-    Settings.RELOOP = Settings.OPTIMIZE = embetter
+    Settings.RELOOP = Settings.MICRO_OPTS = embetter
     Settings.QUANTUM_SIZE = quantum_size
     Settings.ASSERTIONS = 1-embetter
     Settings.SAFE_HEAP = 1-(embetter and llvm_opts)
@@ -4505,7 +4505,7 @@ else:
 
   class benchmark(RunnerCore):
     def setUp(self):
-      Settings.RELOOP = Settings.OPTIMIZE = 1
+      Settings.RELOOP = Settings.MICRO_OPTS = 1
       Settings.USE_TYPED_ARRAYS = 1
       Settings.QUANTUM_SIZE = 1
       Settings.I64_MODE = 0
diff --git a/tools/shared.py b/tools/shared.py
index fa6475b60..f720e890e 100644
--- a/tools/shared.py
+++ b/tools/shared.py
@@ -265,7 +265,7 @@ class Building:
 
     # Run Emscripten
     exported_settings = {}
-    for setting in ['QUANTUM_SIZE', 'RELOOP', 'OPTIMIZE', 'ASSERTIONS', 'USE_TYPED_ARRAYS', 'SAFE_HEAP', 'CHECK_OVERFLOWS', 'CORRECT_OVERFLOWS', 'CORRECT_SIGNS', 'CHECK_SIGNS', 'CORRECT_OVERFLOWS_LINES', 'CORRECT_SIGNS_LINES', 'CORRECT_ROUNDINGS', 'CORRECT_ROUNDINGS_LINES', 'INVOKE_RUN', 'SAFE_HEAP_LINES', 'INIT_STACK', 'PGO', 'EXPORTED_FUNCTIONS', 'EXPORTED_GLOBALS', 'BUILD_AS_SHARED_LIB', 'INCLUDE_FULL_LIBRARY', 'RUNTIME_TYPE_INFO', 'DISABLE_EXCEPTION_CATCHING', 'TOTAL_MEMORY', 'FAST_MEMORY', 'EXCEPTION_DEBUG', 'PROFILE', 'I64_MODE', 'EMULATE_UNALIGNED_ACCESSES']:
+    for setting in ['QUANTUM_SIZE', 'RELOOP', 'MICRO_OPTS', 'ASSERTIONS', 'USE_TYPED_ARRAYS', 'SAFE_HEAP', 'CHECK_OVERFLOWS', 'CORRECT_OVERFLOWS', 'CORRECT_SIGNS', 'CHECK_SIGNS', 'CORRECT_OVERFLOWS_LINES', 'CORRECT_SIGNS_LINES', 'CORRECT_ROUNDINGS', 'CORRECT_ROUNDINGS_LINES', 'INVOKE_RUN', 'SAFE_HEAP_LINES', 'INIT_STACK', 'PGO', 'EXPORTED_FUNCTIONS', 'EXPORTED_GLOBALS', 'BUILD_AS_SHARED_LIB', 'INCLUDE_FULL_LIBRARY', 'RUNTIME_TYPE_INFO', 'DISABLE_EXCEPTION_CATCHING', 'TOTAL_MEMORY', 'FAST_MEMORY', 'EXCEPTION_DEBUG', 'PROFILE', 'I64_MODE', 'EMULATE_UNALIGNED_ACCESSES']:
       try:
         value = eval('Settings.' + setting)
         if value is not None: