On Tuesday, October 28th, during the early hours of trading on the U.S. stock market, Apple's share price experienced a nearly 0.4% uptick at one juncture, briefly catapulting its market capitalization beyond the $4 trillion mark and crowning it as only the third company in history to achieve this monumental feat. Meanwhile, Microsoft's stock price soared by over 4.1% in the initial trading phase, later stabilizing at around a 2% increase, also propelling its market value above the $4 trillion threshold. It had briefly crossed this milestone on July 31st but was unable to sustain the gain until the market closed. On the same day, Microsoft and OpenAI unveiled the signing of a fresh agreement, with Microsoft currently possessing investment stakes valued at roughly $135 billion, translating to a diluted convertible share ratio of approximately 27%.

Apple's stock price ascent was fueled by optimistic forecasts for the new iPhone models and a relaxation of tariff pressures. Since bottoming out in April, Apple's stock price has staged a remarkable comeback, surging by over 56% and augmenting its market value by an estimated $1.4 trillion. Analysts anticipate the imminent arrival of a 'device upgrade boom'. Analysts from Wedbush Securities hailed Apple's entry into the $4 trillion market value club as a pivotal moment. Analysts from Loop Capital elevated Apple's rating and target price. Nevertheless, both Apple and Microsoft's market valuations still trail behind Nvidia's. As of the time of reporting, Nvidia's stock price had climbed by nearly 1.7%, boasting a market value of approximately $4.73 trillion.