How long should a CV actually be?
Two pages is the working default for most people, and one page is better early in a career. The reasoning is not a rule handed down from anywhere; it reflects how the document is actually read.
Initial screening is fast. Studies of recruiter behaviour repeatedly find first-pass reading measured in seconds, spent establishing whether the candidate is plausibly relevant. Length beyond that point does not add information, it dilutes it, because the strongest evidence competes with weaker material.
The practical rule that produces the right length without counting pages is to include what is relevant to the specific role and cut what is not. A twenty-year career does not require twenty years of detail: recent roles deserve substance, older ones a line each, and anything unrelated can go entirely.
There are legitimate exceptions. Academic and research roles expect a longer document including publications and funding. Some public sector and international applications have their own conventions. Senior technical roles may warrant a third page. These are exceptions with reasons, not licence in general.
What consumes space without earning it: a lengthy personal statement of generic adjectives, full addresses, dates of birth, photographs in markets where they are not conventional, school-level qualifications once you have a degree and experience, and lists of responsibilities rather than achievements.
The most valuable edit is converting duties into outcomes. What you were responsible for describes a job; what changed because you held it describes you. The second is shorter and far more persuasive, which is why good CVs tend to get shorter as they get better.