Our XHR implementation is hugely out of date when compared to modern web browsers.

The standard that our XHR implementation adheres the closest too is the XHR Level 1 standard (by W3C back in 2007): https://www.w3.org/TR/2007/WD-XMLHttpRequest-20071026

But there are still discrepancies between our implementation and the specification above.

Our implementation has the response and responseType members, which were added in XHR Level 2 (2011): https://www.w3.org/TR/2011/WD-XMLHttpRequest2-20110816/

Note that the W3C standard has been discontinued in favor of the WHATWG standard: https://www.w3.org/TR/XMLHttpRequest/

Our XHR implementation should ideally adhere to this standard as well, but if that is too big of a goal, then we could start by dealing with the discrepancies between the qt implementation and the final PRE-WHATWG W3C standard.