Tim Cook has stepped down as chief executive officer of Apple after a 15-year tenure, handing over leadership to John Ternus, who officially assumed the role on Tuesday. Cook, 65, will remain with the company as executive chairman, focusing on broader strategic and policy engagement, while Ternus, the 51-year-old head of Apple’s hardware division, steps into a critical period marked by several significant challenges and product launches.

Cook’s time at Apple began shortly before the passing of co-founder Steve Jobs and saw the company transform into one of the world’s most valuable and influential technology firms. Under his leadership, Apple’s shares surged by more than 2,000 percent, returning over $1 trillion to shareholders through buybacks and dividends. The company’s workforce nearly tripled to approximately 166,000 employees, and its retail presence expanded to 535 stores across 27 countries and regions.

Apple shipped around 3.1 billion iPhones during Cook’s tenure, a figure that symbolizes the company’s global reach and deep market penetration. The iPhone remains central to Apple’s business, accounting for about half of the company’s revenue, with over 2.5 billion active Apple devices in use worldwide—a substantial increase from the hundreds of millions in 2011.

Cook’s operational approach focused on refining Apple’s supply chain to maintain high profit margins and exerting tight control over its ecosystem, especially in the area of user privacy. The company made significant strides in developing its own silicon chips, moving away from third-party suppliers, which contributed to increasing gross margins from roughly 40 percent in 2011 to nearly 50 percent today.

Nevertheless, Cook’s leadership has faced criticism and obstacles. His strategy of relying heavily on manufacturing in China made Apple vulnerable to geopolitical tensions, particularly amid trade disputes between Washington and Beijing. Approximately 90 percent of Apple’s suppliers were based, at least in part, in China or Taiwan as of 2024, exposing the company to risks from tariffs and regulatory pressures.

In addition, Apple’s innovation pace under Cook drew mixed reviews. While the company introduced successful new products like the Apple Watch and AirPods, its core lineup of iPhone, Mac, and iPad remained largely unchanged since 2011. Some ventures, such as the Apple Car project, were ultimately discontinued, and products like the HomePod smart speaker and Vision Pro headset achieved only niche success.

A key challenge Cook leaves for Ternus is Apple’s positioning in the evolving artificial intelligence arena. The company has been viewed as cautious in the AI race, opting to incorporate external AI technologies from OpenAI and Google rather than develop large-scale proprietary models or data centers. This cautious approach contributed to a problematic launch of Apple Intelligence in 2024, resulting in investor uncertainty about Apple’s AI roadmap and its potential to drive future service revenue.

Apple’s expanding services business — including offerings like Apple Pay, iCloud, the App Store, and Apple Music — grew from an insignificant contributor in 2011 to generate around $18 billion annually in subscriptions. Yet, regulatory scrutiny has intensified during Cook's era, particularly in Europe. Apple has faced billions in fines related to antitrust investigations, and disputes over compliance with EU legislation, such as the Digital Markets Act, have delayed the launch of key products like the AI-enhanced Siri voice assistant in Europe.

Cook navigated complex relations with governments and policymakers worldwide, building Apple’s presence in China while also fostering connections in Washington, D.C. He was known for his engagement with lawmakers across political lines and managed the company through tumultuous moments such as the imposition of trade tariffs under the Trump administration, which temporarily wiped billions off Apple’s market value.

The leadership transition includes challenges such as managing recent price increases stemming from a global chip shortage and maintaining demand for core products amid evolving market conditions. Ternus is expected to oversee the upcoming rollout of Apple’s first foldable iPhone and the refinement of its Siri AI platform, both seen as pivotal for sustaining Apple’s competitive edge.

Cook was honored with a farewell event at Apple’s Cupertino headquarters, attended by company executives, family, and notable figures including Laurene Powell Jobs, widow of Steve Jobs. Known for his privacy, Cook addressed the gathering and expressed gratitude toward the Apple community as he prepared to shift focus toward his new role and personal pursuits.

As Cook begins his next chapter, Apple faces a future shaped by the foundations he built and the emerging challenges his successor must navigate in an increasingly complex technological and regulatory landscape.