The Customer Who Was a Quarter of the YearThin moat

SK hynix (SKHY) — moat facet

A buyer whose memory purchasing is a line inside a capital-expenditure budget can be revised at a board meeting, which is a different dependence from a consumer cycle.

SK hynix's largest customer represented 23.9% of its revenue in 20251. The filing does not say who it is.

Customers above 10% of revenue, first half (%)27.31%H1 2025, A13.35%H1 2026, A13.03%H1 2026, BSK hynix semi-annual business report, H1 2026, segment note
One customer was over a quarter of the half-year; now two sit just above a tenth.

Reasoning about the shape rather than the identity is the honest approach, and the shape is informative. A buyer of that scale, in a year when the growth came almost entirely from high-bandwidth memory, is not a diversified electronics manufacturer working through a product cycle. It is an organisation whose purchasing is set by a capital-expenditure budget, revised annually, and revised in one direction or the other very quickly.

That is a different kind of dependence from the one memory makers historically carried. A smartphone maker buying a quarter of your output is exposed to consumer demand, which moves gradually and is forecastable. A buyer whose memory purchasing is a line inside an AI infrastructure budget is exposed to a conviction about future demand, which can be revised at a board meeting.

There is no contractual mitigation. SK hynix's own report states that volumes and prices are agreed monthly and quarterly and that it holds no order backlog based on long-term supply contracts2 — so what protects the revenue is the buyer's fear of shortage, not a signature.

The number to watch is not the percentage. It is whether the largest customer's own capital-expenditure guidance is still rising, because that is the input to SK hynix's revenue with a two-to-three-quarter lag.

Moat trajectory: Holding steady

The dependence is large and roughly steady in character: a buyer whose purchasing is a line inside a capital-expenditure budget, revised annually.

The number that tests this moat
Reported
Customers above 10% of first-half revenue
2 in H1 2026 (13.35% and 13.03%), from 1 a year earlier

The filing names no customers, only their share and location. Two large customers of similar size is less concentrated than one at over a quarter of revenue; a return to one dominant buyer would reverse that.

Source: SK hynix semi-annual report, H1 2026 ↗
References
  1. ReportedThe largest customer represented 23.9% of revenue in 2025.
    SK hynix Inc., Form 424B4 prospectus — risk factors and the offering (SEC, CIK 2120882). 'A substantial portion of our sales is attributable to a limited number of customers located in the United States and China. Our two largest customers represented 14.8% and 12.4%, respectively, of our total revenue in the first quarter of 2026 and our largest customer represented 23.9% of our total revenue in 2025.' DRAM products were 77.3% of total sales in Q1 2026 and 77.1% in 2025; NAND flash 22.0% and 21.3%. NAND mass production is transitioning from 176-layer technology to 238- and 321-layer technologies. The offering was 177,900,000 ADSs at US$149.00 each, representing 17,790,000 common shares against 712,702,365 outstanding, each ADS one-tenth of a share; Baillie Gifford Overseas, funds managed by Coatue Management and Situational Awareness Partners indicated a non-binding interest of up to US$7 billion. — FY2025 and Q1 2026 · publ. 2026-07-10 · source ↗
  2. ReportedVolumes and prices are agreed monthly and quarterly, with no order backlog based on long-term supply contracts.
    SK hynix Inc., semi-annual business report for the six months to 30 June 2026 (SEC Form 6-K, 18 August 2026) — 'The Company determines supply volumes and prices on a monthly and quarterly basis by mutual agreement with major customers, and there is no order backlog based on long term supply contracts.' Total equity W 262,693,228 million at 30 June 2026 against W 120,666,751 million at 31 December 2025; cash and cash equivalents, short-term financial instruments and short-term investment assets W 87,957,923 million against W 34,942,253 million; total borrowings W 18,586,634 million against W 22,247,905 million; debt-to-equity 32.80%, net borrowing ratio not disclosed because it is negative. For the six months to 30 June 2026, revenues of W 17,608,702 million (13.35%) and W 17,187,421 million (13.03%) were derived from external Customers A and B respectively; for the six months to 30 June 2025, W 10,890,639 million (27.31%) came from Customer A. IDC market share: DRAM 29.9% in 2023, 33.4% in 2024, 34.8% in 2025 and 29.1% in Q1 2026; NAND 19.6%, 21.4%, 20.9% and 18.5%. Gartner's world DRAM market: US$78.7bn in 2022 (-15.4%), US$49.9bn in 2023 (-36.5%), US$91.6bn in 2024 (+82.7%) and US$146.9bn in 2025 (+60.0%). Announced investments include approximately W 15 trillion for M15X in Cheongju, approximately W 19 trillion for the P&T7 advanced packaging plant and W 21,608.1 billion for Yongin, against long-term plans of roughly W 600 trillion for the Yongin cluster and W 100 trillion for Cheongju. The company developed the world's first 321-layer QLC NAND. China's State Administration for Market Regulation cleared the Intel NAND acquisition conditionally, obliging the group to maintain a reasonable pricing policy, increase production and support the entry of third-party competitors into the Chinese eSSD market for five years from December 2021. — six months to 30 June 2026 · publ. 2026-08-18 · source ↗
Sources
Generated September 23, 2026