Magento 2 REST API returns JSON in Chrome, but XML in Firefox

Question

Today I've discovered a strange thing. When I create an XHR request in Chrome to the REST API, it returns JSON data.

However, the same request in Firefox returns XML data. If I open the URL directly in Chrome, it's XML as well.

I couldn't find anything about this in the REST documentation of Magento 2. So how can I set my XHR request the return always JSON?

Answer 1

Aha, it turns out I have to send an additional header in my XHR request in order to force JSON:

xhr.setRequestHeader("Accept", "*/*");
xhr.setRequestHeader("Content-type", "application/json");

Hopefully this saves somebody else a couple of hours...

Answer 2

Just use storage.get() after requiring mage/storage which will set the appropriate headers