"Above the fold" comes from newspapers — the top half of the front page, visible on newsstands. On the web, it's whatever is visible when the page first loads, before anyone scrolls.
It matters more than any other section of your page. Research from the Nielsen Norman Group shows users spend 57% of their viewing time above the fold and 74% within the first two screenfuls. In our analysis data, First Impression (which is almost entirely above-the-fold content) accounts for 20% of the total conversion score.
What belongs above the fold
Three things, in order of priority: (1) A clear headline that communicates your value proposition, (2) A visible primary CTA, and (3) Enough context to understand what you offer. Everything else — features, testimonials, pricing — can go below. The hero's job is to earn the scroll, not close the sale.
The biggest mistake we see: cramming too much above the fold. Navigation with 12 items, a headline, a subheadline, three CTAs, a video, a logo bar, and a chat widget — all fighting for attention in 800 pixels of vertical space. When everything screams for attention, nothing gets it.
Practical test: Screenshot your page at 1280x800 viewport. Squint at it. Can you identify the headline and the CTA within 2 seconds? If not, simplify.