Vancouver is fairly short. See this guide. It is particularly common in medicine.
In terms of in-text citations, it is short.
- It uses numbers as citations.
- There are variations. But the shortest is to put the numbers as superscripts without parentheses. You can also include ranges like
1-5 for five references.
In terms of the actual references, Vancouver is also quite terse:
- It uses journal abbreviations, so the length of each citation is often shorter
- It doesn't require dois
- End page numbers often omit the leading number e.g., 258-60 would indicate 258 to 260
- It omits full stops after author initials
- It omits comma between author surname and initial
It is worth noting that many of these features will reduce character counts and page counts but not word counts. E.g., using "J" rather than "Journal" in the journal name will not remove a word. Thus, the benefits of these tweaks in terms of giving you space to add additional content will depend on whether your constraints are defined relative to word count or page count.
As an aside, I think the ease with which you can include heaps of references using Vancouver is a major reason why medical journals have higher impact factors.