Microsoft was the first company to surpass a $500 billion market capitalization during the 1990s technology boom.
Microsoft crossed the $500 billion valuation level in 1999, when enthusiasm for personal computers, business software, and the rapidly expanding internet pushed technology shares higher. Windows and Office gave Microsoft unusually broad reach across home and corporate computing.
The milestone occurred during the dot-com era, when investors placed very high valuations on companies connected to the internet and digital technology. Microsoft itself was not primarily an internet company; its core businesses were operating systems, productivity software, and developer tools.
Market-cap milestones from the late 1990s should not be compared directly with later ones without considering inflation, share splits, and changes in the number of shares outstanding. The figure measures equity value at market prices, not enterprise value or annual revenue.