diff --git a/runtime/bigarray.js b/runtime/bigarray.js
index 9f97256217..e23a17c37f 100644
--- a/runtime/bigarray.js
+++ b/runtime/bigarray.js
@@ -99,7 +99,7 @@ Ml_Bigarray.prototype.caml_custom = caml_ba_custom_name;
 Ml_Bigarray.prototype.offset = function (arg) {
   var ofs = 0;
   if(typeof arg === "number") arg = [arg];
-  if (! (arg instanceof Array)) caml_invalid_argument("bigarray.js: invalid offset");
+  if (! (Array.isArray(arg))) caml_invalid_argument("bigarray.js: invalid offset");
   if (this.dims.length != arg.length)
     caml_invalid_argument("Bigarray.get/set: bad number of dimensions");
   if(this.layout == 0 /* c_layout */) {
@@ -269,7 +269,7 @@ function Ml_Bigarray_c_1_1(kind, layout, dims, buffer) {
 Ml_Bigarray_c_1_1.prototype = new Ml_Bigarray()
 Ml_Bigarray_c_1_1.prototype.offset = function (arg) {
   if(typeof arg !== "number"){
-    if((arg instanceof Array) && arg.length == 1)
+    if((Array.isArray(arg)) && arg.length == 1)
       arg = arg[0];
     else caml_invalid_argument("Ml_Bigarray_c_1_1.offset");
   }
diff --git a/runtime/compare.js b/runtime/compare.js
index bea052f414..38d76ae4fe 100644
--- a/runtime/compare.js
+++ b/runtime/compare.js
@@ -21,7 +21,7 @@ function caml_compare_val_tag(a){
   if (typeof a === "number") return 1000; // int_tag (we use it for all numbers)
   else if (caml_is_ml_bytes(a)) return 252; // string_tag
   else if (caml_is_ml_string(a)) return 1252; // ocaml string (if different from bytes)
-  else if (a instanceof Array && a[0] === (a[0]>>>0) && a[0] <= 255) {
+  else if (Array.isArray(a) && a[0] === (a[0]>>>0) && a[0] <= 255) {
     // Look like an ocaml block
     var tag = a[0] | 0;
     // ignore double_array_tag because we cannot accurately set
diff --git a/runtime/fs_fake.js b/runtime/fs_fake.js
index c4d7006a99..4030f4a1b4 100644
--- a/runtime/fs_fake.js
+++ b/runtime/fs_fake.js
@@ -245,7 +245,7 @@ MlFakeDevice.prototype.register= function (name,content){
     file = new MlFakeFile(content);
   if(caml_is_ml_string(content))
     file = new MlFakeFile(caml_bytes_of_string(content));
-  else if(content instanceof Array)
+  else if(Array.isArray(content))
     file = new MlFakeFile(caml_bytes_of_array(content));
   else if(typeof content === "string")
     file = new MlFakeFile(caml_bytes_of_jsbytes(content));
diff --git a/runtime/hash.js b/runtime/hash.js
index 818feb2e1b..fca874c754 100644
--- a/runtime/hash.js
+++ b/runtime/hash.js
@@ -29,7 +29,7 @@ function caml_hash_univ_param (count, limit, obj) {
   function hash_aux (obj) {
     limit --;
     if (count < 0 || limit < 0) return;
-    if (obj instanceof Array && obj[0] === (obj[0]|0)) {
+    if (Array.isArray(obj) && obj[0] === (obj[0]|0)) {
       switch (obj[0]) {
       case 248:
         // Object
@@ -206,7 +206,7 @@ function caml_hash (count, limit, seed, obj) {
         num --;
       }
     }
-    else if (v instanceof Array && v[0] === (v[0]|0)) {
+    else if (Array.isArray(v) && v[0] === (v[0]|0)) {
       switch (v[0]) {
       case 248:
         // Object
diff --git a/runtime/jslib.js b/runtime/jslib.js
index 23e5a1a994..8212344a55 100644
--- a/runtime/jslib.js
+++ b/runtime/jslib.js
@@ -131,7 +131,7 @@ function caml_jsoo_flags_effects(unit){
 //Requires: caml_global_data,caml_string_of_jsstring,caml_named_value
 function caml_wrap_exception(e) {
   if (FLAG("excwrap")) {
-    if(e instanceof Array) return e;
+    if(Array.isArray(e)) return e;
     var exn;
     //Stack_overflow: chrome, safari
     if(globalThis.RangeError
diff --git a/runtime/marshal.js b/runtime/marshal.js
index cb654f2ff8..5929e3df4e 100644
--- a/runtime/marshal.js
+++ b/runtime/marshal.js
@@ -687,7 +687,7 @@ var caml_output_val = function (){
         writer.size_32 += 2 + ((sz_32_64[0] + 3) >> 2);
         writer.size_64 += 2 + ((sz_32_64[1] + 7) >> 3);
       }
-      else if (v instanceof Array && v[0] === (v[0]|0)) {
+      else if (Array.isArray(v) && v[0] === (v[0]|0)) {
         if (v[0] == 251) {
           caml_failwith("output_value: abstract value (Abstract)");
         }
diff --git a/runtime/obj.js b/runtime/obj.js
index 7d3bfee3c9..db7ed9cbc3 100644
--- a/runtime/obj.js
+++ b/runtime/obj.js
@@ -29,13 +29,13 @@ function caml_alloc_dummy_infix () {
 }
 
 //Provides: caml_obj_is_block const (const)
-function caml_obj_is_block (x) { return +(x instanceof Array); }
+function caml_obj_is_block (x) { return +(Array.isArray(x)); }
 
 
 //Provides: caml_obj_tag
 //Requires: caml_is_ml_bytes, caml_is_ml_string
 function caml_obj_tag (x) {
-  if ((x instanceof Array) && x[0] == (x[0] >>> 0))
+  if ((Array.isArray(x)) && x[0] == (x[0] >>> 0))
     return x[0]
   else if (caml_is_ml_bytes(x))
     return 252
@@ -173,7 +173,7 @@ function caml_obj_update_tag(b,o,n) {
 //Provides: caml_lazy_update_to_forcing
 //Requires: caml_obj_update_tag
 function caml_lazy_update_to_forcing(o) {
-  if ((o instanceof Array) && o[0] == (o[0] >>> 0) &&
+  if ((Array.isArray(o)) && o[0] == (o[0] >>> 0) &&
       caml_obj_update_tag(o, 246, 244)) {
     return 0;
   } else {
diff --git a/runtime/parsing.js b/runtime/parsing.js
index 406f7c8498..9a3808e4f4 100644
--- a/runtime/parsing.js
+++ b/runtime/parsing.js
@@ -98,7 +98,7 @@ function caml_parse_engine(tables, env, cmd, arg)
   function print_token(state, tok)
   {
     var token, kind;
-    if (tok instanceof Array) {
+    if (Array.isArray(tok)) {
       token = token_name(tables[tbl_names_block], tok[0]);
       if (typeof tok[1] == "number")
         kind = "" + tok[1];
@@ -150,7 +150,7 @@ function caml_parse_engine(tables, env, cmd, arg)
       /* The ML code calls the lexer and updates */
       /* symb_start and symb_end */
     case 1://TOKEN_READ:
-      if (arg instanceof Array) {
+      if (Array.isArray(arg)) {
         env[env_curr_char] = tables[tbl_transl_block][arg[0] + 1];
         env[env_lval] = arg[1];
       } else {
diff --git a/runtime/sys.js b/runtime/sys.js
index 92c402bbd7..7107cd6852 100644
--- a/runtime/sys.js
+++ b/runtime/sys.js
@@ -83,7 +83,7 @@ function caml_format_exception(exn){
 //Provides: caml_fatal_uncaught_exception
 //Requires: caml_named_value, caml_format_exception, caml_callback
 function caml_fatal_uncaught_exception(err){
-  if(err instanceof Array && (err[0] == 0 || err[0] == 248)) {
+  if(Array.isArray(err) && (err[0] == 0 || err[0] == 248)) {
     var handler = caml_named_value("Printexc.handle_uncaught_exception");
     if(handler) caml_callback(handler, [err,false]);
     else {
diff --git a/runtime/weak.js b/runtime/weak.js
index 025aefd23b..3da6511000 100644
--- a/runtime/weak.js
+++ b/runtime/weak.js
@@ -106,7 +106,7 @@ function caml_ephe_get_key_copy(x, i) {
   var y = caml_ephe_get_key(x, i);
   if (y === 0) return y;
   var z = y[1];
-  if (z instanceof Array) return [0, caml_obj_dup(z)];
+  if (Array.isArray(z)) return [0, caml_obj_dup(z)];
   return y;
 }