Microsoft became the world’s most valuable company by market capitalization during the dot-com boom in 1999.
Microsoft’s valuation surged as investors expected personal computers, Windows, and internet-related software to drive continuing growth. Its dominant desktop operating system and Office productivity suite gave it powerful positions in both consumer and business computing.
The company’s shares reached a peak market capitalization of roughly $600 billion during the technology boom. That figure was enormous for its era, although it is not directly comparable with modern market caps without adjusting for inflation and changes in the size of global equity markets.
Microsoft’s market value later fell sharply after the dot-com bubble burst. The episode illustrates that market capitalization reflects investor expectations as well as current earnings.