Seoul — July 31, 2026. Published after the market close; prices are official closing values.
The 30-second version
- The KOSPI jumped 17.91% to 6,595.45 — a gain of 1,001.89 points and, per local reporting, the largest one-day rise in the index’s history in both point and percentage terms. The KOSDAQ climbed 11.63% to 719.76.
- The trigger: strong results from US big tech, led by Microsoft, calmed fears about AI investment returns. The Philadelphia Semiconductor Index surged 8.19% overnight, and Korean chipmakers followed — SK hynix rose 29.95%, hitting its daily price limit, and Samsung Electronics gained 26.81%.
- Foreign investors bought roughly KRW 5.78 trillion (about $4.1 billion) of KOSPI shares today, while retail investors sold about KRW 8.33 trillion (about $5.8 billion) into the bounce.
- Buy-side “sidecars” — brief automatic pauses on program trading — fired on both markets right after the open, a mirror image of the sell-side halts that marked this week’s crash.
- The won strengthened too: USD/KRW closed the Seoul session at 1,424.0, down 13.4 won.
A record rebound after a record rout
To understand today, you need the two weeks before it. The KOSPI stood at 7,284.41 on July 15. It then fell in a series of violent legs — down 6.37% on July 16, down 10.84% on July 28, down another 5.98% on July 29 — bottoming at 5,593.56 on July 30, a drop of roughly 23% in eleven sessions. July 28 and 29 saw circuit breakers triggered on both the KOSPI and KOSDAQ on two consecutive days, something that had never happened before. A circuit breaker halts trading across the entire market when the index falls past a set threshold — think of it as pulling the fire alarm so everyone can catch their breath.
Today the fire alarm rang in the opposite direction. Minutes after the open, buy-side sidecars activated on both markets — the first simultaneous activation in eleven trading days. A sidecar is a milder cousin of the circuit breaker: when index futures move too sharply, program (algorithmic) orders are paused for five minutes, like a speed bump for automated trading. This one triggered because futures were surging, not collapsing.
Why it happened: AI earnings relief from New York
The spark came from the previous US session. Microsoft’s strong earnings eased a worry that had been weighing on the entire AI trade — that massive AI spending might not pay off. The Nasdaq rose 2.78%, and chip stocks went vertical: Micron gained 18.4%, SanDisk 26.0%, and the Philadelphia Semiconductor Index closed up 8.19%.
Korea, whose market is dominated by memory-chip makers, is arguably the most leveraged major market to that story. SK hynix soared 29.95% to 1,718,000 won, pinning the 30% daily price limit that Korean exchanges impose on individual stocks (a stock simply cannot trade beyond plus or minus 30% in one session). Samsung Electronics jumped 26.81% to 262,500 won, and chip-equipment maker Hanmi Semiconductor added 27.98%. In a scene local media called unprecedented, Samsung Electro-Mechanics (+29.92%) and SK Square (+29.91%) also finished at or near their limits — meaning the market’s second-, third-, and fourth-largest companies all hit the ceiling on the same day.
The rally was broad, not just chips. All seven KODEX sector-ETF proxies we track advanced (these are ETFs used as stand-ins for sector indices, so figures may deviate slightly from official readings): securities firms +11.51%, construction +9.10%, autos +7.36%, bio +6.94%, steel +6.26%, secondary batteries +6.06%. Banks lagged at +1.06%. Hyundai Motor gained 10.54% and Kia 9.19%. The overnight tone had been telegraphed by US-listed Korea proxies: the iShares MSCI South Korea ETF (EWY) rose 11.79% in the prior US session.
Who bought, who sold — and what’s still on the sidelines
Today’s KOSPI flow data showed foreign investors as net buyers of about KRW 5.78 trillion (roughly $4.1 billion at today’s rate; some tallies put the figure even higher), with institutions adding KRW 2.61 trillion (about $1.8 billion). Retail investors went the other way, selling a striking KRW 8.33 trillion (about $5.8 billion) — large-scale profit-taking and relief-selling after the crash.
Some context from the prior session: on July 30, across KOSPI and KOSDAQ combined, foreigners were already net buyers of KRW 1.33 trillion while individuals sold KRW 1.43 trillion — an early sign the tide was turning. But the bigger picture is still cautious: foreigners’ five-day cumulative flow remains a net sale of KRW 10.57 trillion (about $7.4 billion). One strong day has not undone the exodus.
There is plenty of dry powder, though. Investor deposits — cash sitting in brokerage accounts, ready to deploy — stood at KRW 109.6 trillion (about $77 billion) as of July 29, while margin-loan balances (retail leverage) were KRW 33.0 trillion (about $23 billion). The won helped sentiment as well, with USD/KRW closing the Seoul session at 1,424.0, down 13.4 won; note that global 24-hour FX feeds showed a slightly different 1,429.80.
Amid the fireworks, earnings season rolled on quietly: HD Hyundai, GC Biopharma, and F&F all filed preliminary results with the DART disclosure system today.
Key closing numbers
| Instrument | Close | Change |
|---|---|---|
| KOSPI | 6,595.45 | +17.91% |
| KOSDAQ | 719.76 | +11.63% |
| Samsung Electronics | KRW 262,500 | +26.81% |
| SK hynix | KRW 1,718,000 | +29.95% (limit up) |
| USD/KRW (Seoul close) | 1,424.0 | -13.4 won |
| Philadelphia SOX (US, Jul 30) | 11,302.99 | +8.19% |
| VIX | 16.82 | -1.58% |
| WTI crude | $82.47 | -1.34% |
What to watch next
- August 1: Korea customs 10-day trade data. The exports flash is the first hard read on whether the real economy matches the market’s newfound optimism.
- Foreign flows. The five-day cumulative figure is still deeply negative (KRW -10.57 trillion). Watch whether today’s buying is the start of a sustained return or a one-day squeeze.
- Volatility itself. After two consecutive circuit-breaker days followed by a record rally, whipsaw risk cuts both ways. More sidecar activations in either direction would signal the market has not yet found its footing.
- Earnings season. More Q2 preliminary results are queued up on DART, including CJ CGV’s scheduled disclosure.
FAQ
Why did the KOSPI rise almost 18% in one day?
Two forces compounded: relief from US big-tech earnings (Microsoft’s results eased fears that AI spending would not pay off, sending US chip stocks sharply higher) and aggressive bargain hunting after the KOSPI had fallen roughly 23% from its July 15 level, including back-to-back circuit-breaker days on July 28-29.
What is a sidecar in the Korean stock market?
A sidecar is an automatic five-minute pause on program (algorithmic) trading, triggered when index futures move too sharply. It is a speed bump, not a full stop — unlike a circuit breaker, which halts the entire market. Today’s sidecars were buy-side, triggered by surging futures.
Did SK hynix hit its daily price limit?
Yes. Korean stocks cannot move more than 30% in either direction in one session, and SK hynix closed up 29.95% at that ceiling. SK Square (+29.91%) and Samsung Electro-Mechanics (+29.92%) finished at or near the limit as well — three of the market’s four largest companies on the same day.
Was this the biggest one-day gain in KOSPI history?
Yes, according to local reporting — the 1,001.89-point, 17.91% advance was the largest on record in both point and percentage terms, coming just one session after the index had closed at 5,593.56.
Disclaimer: This is an information and analysis publication, not investment advice. See our Methodology for data sources, standards, and our corrections policy.