This is a digital version of the official authoritative stroke order standard used in China. It is sorted by stroke and is not searchable, so it's a bit hard to use. Thus, other resources will often be faster, but if you have dispute with someone about correct stroke order, this document will give you the officially sanctioned answer, published by the Ministry of Education.
To look something up here, first count the number of strokes, then find the page that starts listing characters with this number of strokes, then look at the first stroke in the character you want to look up and find where that stroke is listed. The order of the different strokes is listed in the introduction, but you get the hang of it pretty quickly. the number each stroke is associated with is also listed below each stroke throughout the document, so you can use that for reference.