Browser!! The browser reads it as Number. If your rest api returns {"id": 1324535222364012585} for example, javascript will try and parse that as number from the response!!!

You can of course, change the api such that it does {"id": "1324535222364012585"} instead and voila, it will no longer try parsing it as number. Or the many other workarounds people have recommended above (like appending a prefix, or using a different encoding), but why is it trying to parse a number thats too big and instead of throwing it just rounds down without telling you????!