Major ClientsThin moat

SK hynix (SKHY) — moat facet

One customer was 23.9 percent of last year's revenue, SK hynix names nobody, and the concentration that actually matters -- one accelerator maker taking most of the HBM -- appears in no table at all.

SK hynix's customer disclosure contains an arithmetic curiosity worth pausing on.

Customer concentration, as disclosed23.9%Largest, 202514.8%Largest, Q1 202612.4%Second, Q1 2026Located in the United States and China. SK hynix names neither of them.
The visible concentration is high. The profit concentration is higher and undisclosed.

For the 2025 financial year, its largest customer accounted for 23.9% of revenue1. In the first quarter of 2026, the two largest accounted for 14.8% and 12.4%2 — which looks, on the face of it, like concentration falling sharply in a matter of months.

It is not, or at least not necessarily. Revenue in that period was growing at a rate that makes any ratio unreliable: the second quarter of 2026 alone produced ₩79,318.7 billion, up 257% on the same quarter a year earlier3. When a denominator triples, a customer can buy considerably more and still shrink as a percentage. Nothing in the disclosure separates a customer that reduced its purchases from one that merely grew slower than the total.

What the filing does say plainly is where these buyers are: the United States and China4. Two countries, currently conducting a technology dispute with each other, between them accounting for the overwhelming majority of a Korean company's revenue.

And the concentration that matters most does not appear in the revenue table at all. It sits inside the product, where a single accelerator maker takes the large majority of the high-bandwidth memory SK hynix produces — the part of the business that generates almost all of the profit.

The reassuring feature of this customer base is that its members are among the most cash-generative enterprises in the world. The uncomfortable feature is that they are all spending on the same conviction, and will stop on the same one.

Moat trajectory: Narrowing

The two largest customers were 14.8% and 12.4% of revenue in the first quarter of 2026 and the largest was 23.9% for 2025 — and the profit concentration, one accelerator maker taking most of the HBM, is tighter than the revenue table shows.

The number that tests this moat
Reported
Largest customer, share of revenue
23.9% of 2025 revenue

The two largest were 14.8% and 12.4% in the first quarter of 2026, and SK hynix names neither. The concentration that matters most is not in this table at all: one accelerator maker takes the large majority of the high-bandwidth memory, which is where essentially all the incremental profit is.

Source: SK hynix Form 424B4 prospectus (10 July 2026) ↗
Dig deeper
DIG DEEPER 01
The Customer Who Was a Quarter of the Year
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…
DIG DEEPER 02
Concentration That Fell Without Anyone Leaving
The largest customer went from 27.3 percent of revenue to 13.4 percent while buying 62 percent more -- which is what a tripling denominator does, and…
DIG DEEPER 03
The Buyer Who Told Its Own Investors Memory Costs Too Much
Nvidia guided its gross margin down to 74 percent because of memory prices -- a customer conceding in public that its supplier has the upper hand, and…
DIG DEEPER 04
Two Countries, and a Dispute Between Them
A customer base disclosed as the United States and China is not diversification; it is one dispute with two addresses.
References
  1. ReportedThe largest customer accounted for 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. ReportedThe two largest customers were 14.8% and 12.4% of revenue in the first quarter of 2026.
    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 ↗
  3. ReportedSecond-quarter 2026 revenue of ₩79,318.7bn, up 256.8% on the same quarter a year earlier.
    SK hynix Inc., preliminary results of operations for the second quarter of 2026 (SEC Form 6-K, 29 July 2026) — revenue W 79,318,746 million, up 50.9% on Q1 2026's W 52,576,287 million and 256.8% on Q2 2025's W 22,231,952 million; operating profit W 60,542,608 million, up 61.0% sequentially and 557.2% year on year, an operating margin of about 76%; profit before income tax W 122,708,355 million; profit for the period W 93,922,593 million. First-half 2026 revenue W 131,895,033 million, operating profit W 98,152,891 million and profit W 134,268,502 million. Prepared on a consolidated basis under K-IFRS and unaudited. — Q2 2026 (quarter ended 30 June 2026) · publ. 2026-07-29 · source ↗
  4. ReportedThe filing places the largest customers in the United States and China.
    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 ↗
Sources
Generated September 23, 2026