As most ASX investors watching the markets today would already know, it's been a tough day to be invested. After the 'Liberation Day' tariff announcements out of the United States this morning, the markets are currently in freefall, with the S&P/ASX 200 Index (ASX: XJO) down a nasty 1.1% at present. But what about the US markets and the 'Magnificent Seven' tech stocks in particular?

Over the past few years, the Magnificent Seven have grown to represent a massive chunk of the entire US market. To demonstrate, right now, Apple Inc (NASDAQ: AAPL), Microsoft Corporation (NASDAQ: MSFT), NVIDIA Corp (NASDAQ: NVDA), Amazon Inc (NASDAQ: AMZN), Alphabet Inc (NASDAQ: GOOG)(NASDAQ: GOOGL), Meta Platforms Inc (NASDAQ: META), and Tesla Inc (NASDAQ: TSLA) represent 30.1% of the S&P 500 Index (SP: .INX). That's seven companies out of 500 that take up nearly a third of the rooms at the S&P 500 hotel.

So, it goes without saying that these companies tend to set the agenda for the entire US stock market.

Trump's Liberation Day announcements were coincidentally made just after the US markets closed this morning (our time). So, we'll have to wait until tonight to see how these announcements go down in regular trading hours. However, the US markets do have after-hours trading, which was in effect for these announcements. Today, let's check out how the Magnificent Seven stocks reacted to Liberation Day in this window.

Liberation Day tariffs wreck Magnificent Seven stock prices

By the time extended trading had closed, Apple stock had dropped 7.14% to US$207.91 a share.

Microsoft stock suffered a 3.05% fall to US$370.50.

Nvidia shares closed 5.68% lower at US$104.15.

The Amazon share price tumbled 6.1% to finish at US$184.06.

Alphabet's Class A stock (GOOGL) was hit with a 3.57% sell-down to US$151.43.

Facebook and Instagram-owner Meta Platforms tanked 4.83% to close extended trading at US$555.70 a share.

And, saving the worst until last, Tesla stock plunged 8.01% to finish at U$260.12.

ASX investors seem to be reading the tea leaves today. The ASX-traded iShares S&P 500 ETF (ASX: IVV) has fallen 1.75% in trading today, down to $58.40 a unit.

The Magnificent Seven-heavy BetaShares Nasdaq 100 ETF (ASX: NDQ) has fared even worse, losing 2.14%. And the Global X FANG+ ETF (ASX: FANG), which has a rough 60% weighting to the 'Mag Seven' (not including Tesla), has shed 2.58%.

It will be very interesting to see how these Magnificent Seven companies react in full trading tonight on the US markets. We could be in for a rough ride.