A sell-off that began on Wall Street on Thursday swept through Asian markets on Friday morning and then hit European openings, as investors weighed fears that the AI boom may be slowing.

Wall Street's worst day for the Nasdaq in 19 months

The tech-heavy Nasdaq index had its worst day in 19 months on Thursday, slumping 5.5% in a broad retreat from technology shares.

• •Chip stocks led the slump, with memory maker SanDisk tumbling by 22% and hard drive maker Western Digital falling by 17%.
• •The Vix fear index jumped by 61% to its highest levels since the early weeks of the Iran war.

Asian markets sink in early Friday trading

The slide carried straight into Friday's Asian session, where Japan's Nikkei 225 index sank 6% and South Korea's Kospi tumbled more than 8% in early trading.

That is how Susannah Streeter, chief investment strategist at Wealth Club, described the mood. She said big worries are colliding, because the build-out of datacentres looks set to slow, which risks shredding the spending spree underpinning the boom just as investors are nervous about returns.

European openings and the FTSE 100 fall

European markets opened lower as sentiment stayed fragile. Germany's Dax opened down 1.5%, France's Cac 40 dropped 1.2% and Spain's Ibex was down 1.1%.

The FTSE 100 fell 1.5%, or 166 points, at the start of trading to 10,615. The FTSE 100 fall was broad, with:

• •AstraZeneca down 2.8%, the biggest faller on the index
• •IAG, the owner of British Airways and Iberia, down 1.5% after it missed profit forecasts in a trading update
• •The miners Antofagasta and Anglo American also among the big fallers

Where indices stand for the year

Despite the losses, most indices are still up for the year. The Nasdaq Composite is still up 4.6% since the start of January, even though it is more than 10% below its peak. The FTSE 100 has gained almost 6.9% in 2026, but it is now more than 300 points below the record high set in July.