I know it means roughly "for your reference", but I can't really grasp why it means that based on my understanding of までに (which I consider roughly as 'before' or 'by'). I can't really come to any kind of reasonable literal translation, could someone elaborate what exactly it's doing in this phrase?
My only guess is something like "before [you] consult [other materials] (look at this)".
Thanks.
This まで corresponds to the following definition of まで of デジタル大辞泉:
３ 動作・事柄がもうそれ以上には及ばず、それに限られる意を表す。…だけ。「気に入らなければ断る―さ」「念のために聞いてみた―だ」
So まで can mean only or just. ご参考までに is "just for your reference", implying that information is not critically important.
Other examples:
- まずはご挨拶まで。
(Used at the end of a formal business letter, and means something like "For now I can only greet, but please allow me to contact you again later")- 取り急ぎ、ご報告まで(申し上げます)。
"This is (only) a quick report. (details will follow)"
まで actually has quite a number of different (but fundamentally related) meanings. Here, IMO, it's related to the "no more than" meaning (a bit like にすぎない) and serves to make this expression more humble: "May this at most serve as a reference for you" aka I feel (or at least make it seem as such to be polite) that it may not be worthy of being used as anything more than a mere reference.
As a related bit, it's actually an abbreviated version of one of a number of possible longer phrases: ご参考までに（～お目【め】通【とお】しください, etc.）
