diff --git a/src/browser/js/Snapshot.zig b/src/browser/js/Snapshot.zig
index c7a33ae95..2e344e7b8 100644
--- a/src/browser/js/Snapshot.zig
+++ b/src/browser/js/Snapshot.zig
@@ -275,10 +275,11 @@ fn createSnapshotContext(
             .data = null,
             .flags = v8.kOnlyInterceptStrings | v8.kNonMasking,
         });
+        const window_index = @import("../webapi/Window.zig").JsApi.index;
         v8.v8__ObjectTemplate__SetIndexedHandler(global_template, &.{
-            .getter = @import("../webapi/Window.zig").JsApi.index.getter,
+            .getter = window_index.getter,
             .setter = null,
-            .query = null,
+            .query = window_index.query,
             .deleter = null,
             .enumerator = null,
             .definer = null,
diff --git a/src/browser/js/bridge.zig b/src/browser/js/bridge.zig
index 1098779c7..099e57d02 100644
--- a/src/browser/js/bridge.zig
+++ b/src/browser/js/bridge.zig
@@ -398,20 +398,25 @@ pub const Indexed = struct {
             }.wrap;
         }
 
-        if (@typeInfo(@TypeOf(query)) != .null) {
-            indexed.query = struct {
-                fn wrap(idx: u32, handle: ?*const v8.PropertyCallbackInfo) callconv(.c) u32 {
-                    const v8_isolate = v8.v8__PropertyCallbackInfo__GetIsolate(handle).?;
-                    var caller: Caller = undefined;
-                    if (!caller.init(v8_isolate)) {
-                        return js.Intercepted.no;
-                    }
-                    defer caller.deinit();
+        const query_func = if (@typeInfo(@TypeOf(query)) != .null)
+            query
+        else
+            // Generate a Query handler by wrapping getter. With no setter, this
+            // gets the ReadOnly attribute
+            GetterQuery(getter, if (@typeInfo(@TypeOf(setter)) == .null) v8.ReadOnly else v8.None).query;
 
-                    return caller.getIndexQuery(T, query, idx, handle.?);
+        indexed.query = struct {
+            fn wrap(idx: u32, handle: ?*const v8.PropertyCallbackInfo) callconv(.c) u32 {
+                const v8_isolate = v8.v8__PropertyCallbackInfo__GetIsolate(handle).?;
+                var caller: Caller = undefined;
+                if (!caller.init(v8_isolate)) {
+                    return js.Intercepted.no;
                 }
-            }.wrap;
-        }
+                defer caller.deinit();
+
+                return caller.getIndexQuery(T, query_func, idx, handle.?);
+            }
+        }.wrap;
 
         if (@typeInfo(@TypeOf(definer)) != .null) {
             indexed.definer = struct {
@@ -433,6 +438,35 @@ pub const Indexed = struct {
     }
 };
 
+// Default index query if one isn't provided. Uses the getter to determine the result
+fn GetterQuery(comptime getter: anytype, comptime attrs: u32) type {
+    const params = @typeInfo(@TypeOf(getter)).@"fn".params;
+    const Self = params[0].type.?;
+    const Index = params[1].type.?;
+    return struct {
+        const query = if (params.len == 3) withGlobal else plain;
+
+        fn plain(self: Self, idx: Index) !u32 {
+            return attributes(getter(self, idx));
+        }
+
+        fn withGlobal(self: Self, idx: Index, global: params[2].type.?) !u32 {
+            return attributes(getter(self, idx, global));
+        }
+
+        fn attributes(ret: anytype) !u32 {
+            const value = switch (@typeInfo(@TypeOf(ret))) {
+                .error_union => try ret,
+                else => ret,
+            };
+            if (@typeInfo(@TypeOf(value)) == .optional and value == null) {
+                return error.NotHandled;
+            }
+            return attrs;
+        }
+    };
+}
+
 pub const NamedIndexed = struct {
     getter: *const fn (c_name: ?*const v8.Name, handle: ?*const v8.PropertyCallbackInfo) callconv(.c) u32,
     setter: ?*const fn (c_name: ?*const v8.Name, c_value: ?*const v8.Value, handle: ?*const v8.PropertyCallbackInfo) callconv(.c) u32 = null,
diff --git a/src/browser/tests/collections/indexed_properties.html b/src/browser/tests/collections/indexed_properties.html
new file mode 100644
index 000000000..3bc7a5d04
--- /dev/null
+++ b/src/browser/tests/collections/indexed_properties.html
@@ -0,0 +1,54 @@
+<!DOCTYPE html>
+<script src="../testing.js"></script>
+<form id=f><input name=i1><select id=s><option>a</option><option>b</option></select></form>
+<div id=d class="x y" data-a=1></div>
+<iframe></iframe>
+
+<script id=supported_indices>
+  {
+    // Web IDL: a supported index is enumerable, configurable and, unless
+    // there's an indexed setter (HTMLOptionsCollection), read-only. An
+    // unsupported one isn't there at all.
+    const d = document.getElementById('d');
+    const cases = {
+      HTMLCollection: document.getElementsByTagName('div'),
+      NodeList: document.querySelectorAll('div'),
+      NamedNodeMap: d.attributes,
+      HTMLOptionsCollection: document.getElementById('s').options,
+      HTMLAllCollection: document.all,
+      HTMLFormControlsCollection: document.getElementById('f').elements,
+      DOMTokenList: d.classList,
+      Window: window,
+    };
+    for (const [name, obj] of Object.entries(cases)) {
+      const desc = Object.getOwnPropertyDescriptor(obj, 0);
+      const writable = name === 'HTMLOptionsCollection';
+      testing.expectEqual([name, true, true, writable].join(' '), [name, desc.enumerable, desc.configurable, desc.writable].join(' '));
+      testing.expectEqual(name + ' true', name + ' ' + obj.propertyIsEnumerable(0));
+      testing.expectEqual(name + ' true', name + ' ' + (0 in obj));
+      testing.expectEqual(name + ' false', name + ' ' + (9999 in obj));
+      testing.expectEqual(name + ' true', name + ' ' + (Object.getOwnPropertyDescriptor(obj, 9999) === undefined));
+    }
+  }
+</script>
+
+<script id=enumeration>
+  {
+    // the query must not filter supported indices out of enumeration
+    const list = document.querySelectorAll('div');
+    testing.expectEqual(['0'], Object.keys(list));
+    const seen = [];
+    for (const k in list) seen.push(k);
+    testing.expectEqual('0', seen[0]);
+  }
+</script>
+
+<script id=read_only>
+  (function() {
+    'use strict';
+    const list = document.querySelectorAll('div');
+    const first = list[0];
+    testing.expectError('TypeError', () => { list[0] = 'x'; });
+    testing.expectEqual(first, list[0]);
+  })();
+</script>
diff --git a/src/browser/tests/element/html/select.html b/src/browser/tests/element/html/select.html
index 603d9a259..811a48350 100644
--- a/src/browser/tests/element/html/select.html
+++ b/src/browser/tests/element/html/select.html
@@ -275,6 +275,44 @@
   }
 </script>
 
+<script id="options_indexed_setter">
+  {
+    const sel = document.createElement('select')
+    const opts = sel.options
+    const make = (v) => { const o = document.createElement('option'); o.value = v; return o }
+
+    // past the end pads with blank options, then appends
+    opts[2] = make('c')
+    testing.expectEqual(3, opts.length)
+    testing.expectEqual(['', '', 'c'], Array.from(opts, (o) => o.value))
+
+    // in range replaces in place, including inside an optgroup (Firefox;
+    // Chrome removes it and add()s the new one before the next option)
+    opts[0] = make('a')
+    testing.expectEqual(['a', '', 'c'], Array.from(opts, (o) => o.value))
+    const group = document.createElement('optgroup')
+    group.appendChild(opts[1])
+    sel.appendChild(group)
+    opts[2] = make('b')
+    testing.expectEqual(group, opts[2].parentNode)
+    testing.expectEqual(['a', 'c', 'b'], Array.from(opts, (o) => o.value))
+
+    // null removes; null past the end is a no-op
+    opts[1] = null
+    testing.expectEqual(['a', 'b'], Array.from(opts, (o) => o.value))
+    opts[10] = null
+    testing.expectEqual(2, opts.length)
+
+    // only options (or null) are accepted
+    testing.expectError('TypeError', () => { opts[0] = document.createElement('div') })
+    testing.expectEqual(2, opts.length)
+
+    const desc = Object.getOwnPropertyDescriptor(opts, 0)
+    testing.expectEqual(true, desc.writable)
+    testing.expectEqual(true, desc.enumerable)
+  }
+</script>
+
 <script id="select_add">
   {
     const sel = document.createElement('select')
diff --git a/src/browser/webapi/collections/HTMLCollection.zig b/src/browser/webapi/collections/HTMLCollection.zig
index 19840795f..e6faf9847 100644
--- a/src/browser/webapi/collections/HTMLCollection.zig
+++ b/src/browser/webapi/collections/HTMLCollection.zig
@@ -347,3 +347,8 @@ pub const JsApi = struct {
     pub const namedItem = bridge.function(HTMLCollection.getByName, .{});
     pub const symbol_iterator = bridge.iterator(HTMLCollection.iterator, .{});
 };
+
+const testing = @import("../../../testing.zig");
+test "WebApi: indexed properties" {
+    try testing.htmlRunner("collections/indexed_properties.html", .{});
+}
diff --git a/src/browser/webapi/collections/HTMLOptionsCollection.zig b/src/browser/webapi/collections/HTMLOptionsCollection.zig
index d317be94d..d3c3baaeb 100644
--- a/src/browser/webapi/collections/HTMLOptionsCollection.zig
+++ b/src/browser/webapi/collections/HTMLOptionsCollection.zig
@@ -104,6 +104,41 @@ pub fn remove(self: *HTMLOptionsCollection, index: i32, frame: *Frame) void {
     }
 }
 
+// Chrome's cap (kMaxListItems): padding up to a huge index would otherwise
+// create that many options.
+const max_list_items = 100_000;
+
+// The indexed setter: null removes the option at index; an index past the
+// end pads with blank options and then appends; otherwise the option at
+// index is replaced.
+fn setAtIndex(self: *HTMLOptionsCollection, index: u32, option_: ?*Option, frame: *Frame) !void {
+    const existing = self.getAtIndex(index, frame);
+    const option = (option_ orelse {
+        if (existing) |element| {
+            element.remove(frame);
+        }
+        return;
+    }).asElement().asNode();
+
+    if (existing) |element| {
+        const old = element.asNode();
+        _ = try old.parentNode().?.replaceChild(option, old, frame);
+        return;
+    }
+
+    if (index >= max_list_items) {
+        return;
+    }
+
+    const select_node = self._select.asNode();
+    const doc = select_node.ownerDocument(frame).?;
+    for (self.length(frame)..index) |_| {
+        const blank = try doc.createElementNS("http://www.w3.org/1999/xhtml", "option", frame);
+        _ = try select_node.appendChild(blank.asNode(), frame);
+    }
+    _ = try select_node.appendChild(option, frame);
+}
+
 pub const JsApi = struct {
     pub const bridge = js.Bridge(HTMLOptionsCollection);
 
@@ -117,7 +152,7 @@ pub const JsApi = struct {
     pub const length = bridge.accessor(HTMLOptionsCollection.length, null, .{});
 
     // Indexed access
-    pub const @"[int]" = bridge.indexed(HTMLOptionsCollection.getAtIndex, null, .{ .null_as_undefined = true });
+    pub const @"[int]" = bridge.indexedReadWrite(HTMLOptionsCollection.getAtIndex, setAtIndex, null, null, null, .{ .null_as_undefined = true, .ce_reactions = true });
     pub const @"[str]" = bridge.namedIndexed(HTMLOptionsCollection.getByName, null, null, null, struct {
         fn wrap(self: *HTMLOptionsCollection, name: []const u8, frame: *Frame) !u32 {
             if (self.getByName(name, frame) != null) {