Smartphones have been around long enough that, to the casual observer, their designs seem to have hit a plateau. And on a functional level, that’s more or less true—we’re all essentially holding the same six-inch-ish rectangle, aside from the occasional foldable exception.

But the maturity and ubiquity of smartphones have sparked a new phenomenon: the return of trends in cycles, much like fashion. For example, most phones released in the past few years have flat sides, like the iPhone 4 from 2010. Five years ago, almost all those sides would have been curved. Flat edges aren’t a new invention—they’re just what’s trending again.

But this year brings a surprising twist, something many thought unlikely to return: For the first time in a while, major phone makers are prioritizing thinness.

Samsung kicked off the year by announcing its Galaxy S25 lineup, which includes a slimline model, the Galaxy S25 Edge. Bloomberg’s Mark Gurman has reported that Apple is planning a thinner 2025 iPhone said to feature a single camera. And smaller brands like Tecno showed off unusually thin phones at last month’s Mobile World Congress.

So, why now?

Around a decade ago, it was common for companies to boast about how thin their phones were. “Here’s the real magic,” said Apple’s Phil Schiller when introducing the larger screens in 2014’s 6.9mm-thick iPhone 6. “Thinner than any phones we’ve ever made—that took an incredible amount of engineering.” A few months later, Oppo announced its R5 phone, which came in at a record-breaking 4.85mm.

Back then, it seemed inevitable that phones would just keep getting thinner. But then something curious happened: The iPhone 6S got thicker, bumping up to 7.1mm and switching to a stronger aluminum alloy. It was an unofficial but obvious response to the iPhone 6’s tendency to bend. (It happened to me.)

No one complained much about the iPhone 6S’s structural integrity, but iPhones kept getting thicker, topping out at the 8.3mm we see with the current iPhone 16 Pro. By and large, people haven’t seemed to mind. Battery life is much less of a concern than it used to be, and today’s increasingly large camera hardware simply wouldn’t fit in thinner devices.

The 2025 flurry of deliberately thin phones, then, is a clear break from recent trends. So why are manufacturers converging on the same idea?

The primary answer may be technical. While we don’t yet know what Samsung or Apple are using in their upcoming devices, silicon-carbon batteries have become increasingly common in Chinese Android phones over the past year. Infusing silicon into the battery chemistry can provide a meaningful increase in capacity within the same volume.

Oppo’s latest Find N5 folding phone, for example, is just 4.2mm thick when unfolded—barely thick enough to accommodate a USB-C port. But its 5,600mAh silicon-carbide battery represents a 17% increase in capacity over its predecessor, the Find N3, even though that phone was 38% thicker. Other companies like Xiaomi and Vivo have used the tech to similar ends.

The other reason thinner phones might take off is more subjective. When was the last time a new phone truly wowed you? There will clearly be trade-offs in battery life and performance with a significantly thinner device. But if you finish each day with more than half a charge, or if you rarely use your telephoto lens, it’s plausible you might prefer a slimmer, more attractive handset.

Combine better battery technology with the fact that most people don’t need flagship-level performance, and suddenly a slim phone with few compromises seems pretty reasonable. It makes sense for companies to carve out space for design-forward devices in their lineups. Samsung has always been willing to experiment; and while Apple tends to be more conservative, it’s reportedly unimpressed with sales of its mid-tier Plus-not-Pro iPhones. Why not try something more distinctive between the entry level and the high end?

If anything, the question is whether these designs will go far enough. Samsung has yet to announce the Galaxy S25 Edge’s specs or let anyone in the media handle it, but I saw it suspended in the air at Mobile World Congress and wasn’t particularly blown away by its dimensions. Bloomberg’s Gurman has suggested the upcoming slim iPhone will be “about 2mm thinner than an iPhone 16 Pro,” putting it around 6.3mm—more in line with the iPhone 6 than today’s thicker models.

Maybe that’s the right tradeoff. The goal here should be to create something like the MacBook Air of phones: impressive design with unspectacular specs that are good enough for most use cases. The Pro models can continue to be for people who really need them.

Plenty of people will always want the most performant phone with the biggest battery and best cameras, of course. But when a phone’s selling point is its physical form, it can’t really be judged until you pick it up for yourself—and then find out how long its battery lasts.

FastCompany