Please note that these tests represent existence, not functionality or full conformance. I hope to test conformance sometime in the future.

IE 7 IE 8 IE 9 IE 10 FF 3 FF 3.5, 3.6 FF 4+ SF 3.2 SF 4 SF 5 SF 5.1 SF 6 WebKit CH 5 CH 6 CH 7-12 CH 13-16 CH 19+ OP 10.1 OP 10.50-11.50 OP 12 OP 12.10 Konq 4.3 Konq 4.9 BESEN Rhino 1.7
§Object.create No No Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes No No Yes Yes
§Object.defineProperty No Yes[1] Yes Yes No No Yes No No Yes[2] Yes Yes Yes[2] Yes Yes Yes Yes Yes No No Yes Yes No No Yes Yes
§Object.defineProperties No No Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes No No Yes Yes
§Object.getPrototypeOf No No Yes Yes No Yes Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes No Yes Yes Yes
§Object.keys No No Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes No Yes Yes Yes
§Object.seal No No Yes Yes No No Yes No No No Yes Yes Yes No Yes Yes Yes Yes No No Yes Yes No No Yes Yes
§Object.freeze No No Yes Yes No No Yes No No No Yes Yes Yes No Yes Yes Yes Yes No No Yes Yes No No Yes Yes
§Object.preventExtensions No No Yes Yes No No Yes No No No Yes Yes Yes No Yes Yes Yes Yes No No Yes Yes No No Yes Yes
§Object.isSealed No No Yes Yes No No Yes No No No Yes Yes Yes No Yes Yes Yes Yes No No Yes Yes No No Yes Yes
§Object.isFrozen No No Yes Yes No No Yes No No No Yes Yes Yes No Yes Yes Yes Yes No No Yes Yes No No Yes Yes
§Object.isExtensible No No Yes Yes No No Yes No No No Yes Yes Yes No Yes Yes Yes Yes No No Yes Yes No No Yes Yes
§Object.getOwnPropertyDescriptor No Yes Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes No No Yes Yes
§Object.getOwnPropertyNames No No Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes No Yes Yes Yes
§Date.prototype.toISOString No No Yes Yes No Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes No No Yes Yes
§Date.now No No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes
§Array.isArray No No Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes No Yes Yes Yes
§JSON No Yes Yes Yes No Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes No Yes Yes Yes
§Function.prototype.bind No No Yes Yes No No Yes No No No No[3] Yes Yes No No Yes Yes Yes No No Yes Yes No No Yes Yes
§String.prototype.trim No No Yes Yes No Yes Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes No Yes Yes Yes
§Array.prototype.indexOf No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.lastIndexOf No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.every No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.some No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.forEach No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.map No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.filter No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.reduce No No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes
§Array.prototype.reduceRight No No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes
§Getter in property initializer No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Setter in property initializer No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Property access on strings[4] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
§Reserved words as property names[5] No No Yes Yes Yes Yes Yes No No No Yes Yes Yes No No Yes Yes Yes No No Yes Yes No No Yes No
§Zero-width chars in identifiers No No Yes Yes No No Yes[6] No No No No Yes Yes No No No No Yes No No No Yes No No Yes Yes
§Immutable undefined No No Yes Yes No No Yes No No Yes Yes Yes Yes No No No No Yes No No Yes Yes No Yes Yes Yes
§Strict mode No No No Yes[7] No No Yes No No No Yes Yes Yes No No No Yes Yes No No Yes Yes No No Yes No

[1] In Internet Explorer 8 Object.defineProperty only accepts DOM objects (MSDN reference).

[2] In some versions of WebKit Object.defineProperty does not work with DOM objects.

[3] Function.prototype.bind is now supported in Safari 5.1.4

[4] For example: "foobar"[3] === "b"

[5] For example: ({ if: 1 })

[6] Firefox 4 & 5 fail this test

[7] IE10 PP2 has a bug with strict mode which makes the following expression "fail", even though strict mode is more or less supported: (function(){ "use strict"; return !this })()