So far in 2025, we've had not one, but two companies achieve a $4 trillion market capitalization. Both Nvidia (NVDA 3.56%) and Microsoft (MSFT 2.18%) have joined this ultra-exclusive club, with Nvidia remaining over that threshold, and there are a few others that aren't too far behind.

If I were to ask you what the largest companies were during the dot-com boom of the late 1990s, you might assume that the top of the list might have a tech stock or two, just like there is today. And you'd be right.

Image source: Getty Images.

However, there are two big differences. The largest companies today are more than an order of magnitude larger than in 1999, and technology doesn't just appear on the list -- it completely dominates it.

With that in mind, here's how the largest companies of 1999 compare with those of 2025.

The five largest companies of 1999

Data source: CNBC.com. Market caps as of 1/1/1999.

The five largest companies of 2025

Data source: CNBC.com. Market caps as of 8/3/2025.

As a final thought, considering the differences between the two lists, it's interesting to consider what the list of the largest companies might look like in another quarter-century. Will the largest companies increase by yet another order of magnitude? And will the tech industry continue to dominate?