Microsoft became the first public company to exceed a $500 billion market capitalization in 1999.
Microsoft passed the $500 billion valuation threshold during the technology boom of 1999. Its market value was powered by the dominance of Windows operating systems and Microsoft Office, which generated substantial software revenue from personal-computer users and businesses.
The company had gone public in 1986, and its stock rose dramatically during the 1990s as personal computers spread worldwide. Microsoft’s valuation milestone came before the dot-com bubble peaked in early 2000 and before the company later shifted toward cloud computing and subscription software.
Market-cap records depend on share prices and share counts, so historical sources may report slightly different dates or intraday values. The 1999 milestone is distinct from Microsoft’s later achievement of joining the trillion-dollar companies.