Microsoft briefly became the world’s most valuable public company in October 2021.
Microsoft overtook Apple by market capitalization during October 2021 trading. The change followed movements in both companies’ share prices, including concerns about supply constraints affecting Apple’s ability to meet iPhone demand.
The ranking did not mean Microsoft had permanently surpassed Apple. Market capitalization is a live market measure, so leadership can change whenever investors revalue either company. Apple later reclaimed the top position at various points, and other companies subsequently entered the contest.
Microsoft’s diversified business helped support its valuation. Its portfolio includes Windows, Microsoft 365, Azure, Xbox, LinkedIn, and enterprise software. A frequent mistake is to treat the ranking as a measure of annual sales; market cap instead reflects investors’ expectations about future earnings, growth, and risk.