From concept to reality, Honor's ambition to create the world's slimmest book-style foldable phone took around two years. That may seem like an eternity in a world as fast-paced as the technology industry.  

But according to Honor, there's a good reason it took a long time to develop the razor-thin Magic V3, the company's fourth-generation foldable phone. Even prior to the official start of development, the company said it invests in research and development of "certain parts" or new materials before formally integrating them into a foldable phone project. By comparison, the development period for a regular Honor smartphone typically lasts 12 to 18 months. The result: A book-style foldable phone that looks strikingly similar to a regular phone when closed.

Winning the foldables race is an important goal for Honor. The worldwide foldable market is forecast to reach 25 million devices by the end of 2024, up 37.6% from the 18.1 million units shipped in 2023, according to research firm the International Data Corporation. By 2028, total foldable phone shipments worldwide are expected to rise to 45.7 million units, IDC predicts, representing a compounded annual growth rate of 20.3% for 2023-2028.

With two of the largest phone makers -- Samsung and Xiaomi -- churning out vastly improved foldables year after year, Honor has a lot of competition. As of this year, virtually every major smartphone producer has launched either a book-style phone, a flip phone or both types of devices. 

Samsung slimmed down the width of the Galaxy Z Fold 6, which it just launched in July, by more than a millimeter. Earlier this month, Google also unveiled its Pixel 9 Pro Fold, which is more compact than its book-style predecessor. Xiaomi, the third-largest phone maker by shipment volume, is nipping at Honor's heels with its equally light and almost equally ultra-thin Mix 4 Fold. Apple, which is characteristically behind in jumping on emerging tech, is rumored to launch a clamshell-style iPhone in 2026.

Honor, once a subsidiary of Chinese tech giant Huawei, clearly sees making its foldables as sleek as possible as being essential to accomplishing that mission. 

Honor said a "stronger and slimmer" design mantra underpinned its journey of developing a foldable phone. And the Magic V3 seems to deliver on that promise, measuring just 9.2 millimeters thick when folded shut. It's slimmer than the Galaxy Z Fold 6, the newly announced Google Pixel 9 Pro Fold and even the Xiaomi Mix Fold 4. 

"With foldables being so slim these days, every millimeter shaved off is a monumental endeavor," Hope Cao, Honor's Magic V3 product expert, told CNET in an exclusive interview ahead of the Magic V3's international launch in September. As product expert, Cao leads the product development of the Magic V3 from start to finish.

The Magic V3 and how Honor designed it

Last year's Magic V2 represented a big leap in Honor's foldable phone progress. The V2 made waves internationally as it raised the bar for portability in book-style foldable phones. For the first time, Honor showed the world that a phone with two displays can have similar proportions to a regular bar phone, which has just one screen of course. 

The Magic V3 builds upon that trajectory. It has a 6.43-inch cover screen that flips over like a book to reveal a 7.92-inch inner screen. It boasts five cameras in total, complete with a periscope-style telephoto lens capable of 3.5x optical zoom. Under the hood, the Magic V3 is equipped with a 5,150-mAh silicon carbon battery, a newer type of battery for smartphones that can be replenished with the 66-watt wired charger that comes inside the box or via a wireless charger with support for 45 watts. 

Those flagship features, among others, are packed into an uber-slim chassis. When folded, the Magic V3 measures just 9.2 millimeters (0.36 inches) and weighs 226 grams -- a design that boasts similar proportions to regular bar phones such as the Samsung Galaxy S24 Ultra and the iPhone 15 Pro Max. In fact, the Magic V3 is actually lighter than the 24 Ultra by several grams. 

"Developing a foldable phone that is as slim and portable in its folded state as a flagship bar phone, while being as powerful and user-friendly in its unfolded state as a mini-pad, will encourage broader adoption of foldable phones in everyday life," Cao told CNET.

But Xiaomi isn't far behind. At 4.59 millimeters when unfolded, it's just a hair thicker than the 4.35mm thick Magic V3. Honor was the world's third largest foldable phone maker as of the first quarter of 2024, tying with Lenovo, which owns Motorola, and trailing after Huawei, according to IDC data provided to CNET. But as the third-biggest player in the broader smartphone market, Xiaomi undoubtedly has a larger overall footprint. 

Like its rivals, Honor said there were several key design considerations to achieving a slimmer build. These include a redesigned hinge that utilizes a lightweight steel, the implementation of new materials such as aerospace special fiber for the back cover of the black-colored model and a stronger aluminum for the frame. Honor also said investing into R&D of batteries ultimately helped the Magic V3 fit a large battery into a thinner frame. 

"In contrast to industry-standard solutions with only one set of swing arms, the Honor Magic V3 adds an extra set of swing arms to the Honor super steel hinge," Cao said. This design enhances the hinge's resilience by 1,250% compared with the Honor Magic V2, Cao claims.

Apart from the hinge, the Magic V3 has 19 new materials across the smartphone's body, display, battery and vapor chamber, which the company claims results in more powerful screens, longer battery performance, increased durability, and more efficient heat dissipation.

"New materials is a major direction that Honor is pursuing," Cao told CNET. "Honor is investing massively into the hinge, or specifically the steel materials as part of the hinge." 

How Honor works around foldable phone compromises

But Honor isn't alone. Foldable phone makers have made significant strides since the first foldable phone debuted in 2019, but durability remains a top concern for consumers. Considering some foldables can set you back as much as $2,000, shoppers expect a phone that lasts for the price. With reports surfacing on Reddit about Magic V2 owners experiencing screen issues, durability is still a top concern. 

In an effort at transparency, Honor offered us an inside look at how it tests its phones for durability. A video filmed exclusively for CNET showed several Magic V3 phones being folded repeatedly with a machine at Honor's Reliability Lab in Shenzhen, China -- sort of like a folding phone boot camp. The lab is equipped with testing devices for spraying, immersion, wear resistance, scratch resistance and corrosion resistance, the company told CNET. Samsung tests their foldable phones in a similar way, at least where folding tests and drop tests are concerned. 

The Honor Magic V3 is tested to withstand 500,000 folds, a notable improvement over its predecessor, the Magic V2, which managed 400,000 folds. However, there's a catch: the Magic V3, along with many rival foldables, lacks a complete IP rating for water and dust resistance. The Magic V3 has an IPX8 rating, which means it can withstand submersion under 1.5 meters of water for up to 20 minutes, the same as Google's new Pixel 9 Pro Fold.

During its China launch, Honor stuck the V3 in a washing machine, and it came out working just fine, although that was a controlled demonstration that may not reflect everyday use. However, the Magic V3 isn't rated for protection against dust ingress, which means taking it to a beach or a desert could be dangerous for your foldable phone. 

No other folding phone is rated to fully keep out dust particles -- aside from the 2023 Motorola Razr Plus, which is protected against dust with an IP54 rating. The Galaxy Z Fold 6, which has an IP48 rating, is protected against solid objects larger than 1mm, but remains susceptible to sand and smaller particles. But dust resistance is a common feature among nonfoldable phones, highlighting another area where foldables like the Magic V3 clearly still have some catching up to do. 

When pressed on its plans for dust resistance, Cao declined to comment, instead saying Honor would make an announcement in "due course". 

Aside from durability, the Magic V3 has another physical compromise: a protruding camera bump that will likely affect its ability to lie flat on hard surfaces. 

To be fair, the Magic V3 isn't alone in bearing this design issue. It appears across numerous foldable phones, including the Pixel Fold, One Plus Open, Galaxy Z Fold 6 and Xiaomi Mix Fold 4. Large camera bumps can also be a feature of regular bar phones with ambitious camera modules. However, it begs the question: How truly portable is a book-style foldable phone if it has this massive bump protruding from its backside?

Analysts say it's a necessary trade-off that likely isn't going away anytime soon. 

"Manufacturers are slimming down the displays, batteries and circuit boards, and they could slim down the camera modules too, but image quality would suffer," Avi Greengart, analyst at Techsponential, told CNET. "They're making the bet that consumers would prefer better pictures and the ability to easily hold the phone while folded over an unsightly camera bump."

With its large camera bump, the Magic V3 boasts a periscope-style telephoto lens that is capable of 100x digital zoom, as part of its rear camera module. In addition, it has four other cameras consisting of a 50-megapixel main camera, a 40-megapixel ultrawide and two front-facing cameras. The main camera has a 1/1.56-inch sensor, which is a small compared with regular bar phones but competitive when stacked up against its foldable phone rivals. 

While it's impossible to fairly assess the Magic V3's camera module without testing it ourselves, foldable phone cameras tend to be a step down in terms of performance and image quality compared with similarly priced nonfolding phones because there's physically less space for larger image sensors and lens elements. Consumers' dollars mainly go toward paying for the phone's flexible display rather than for the kind of top-of-the-line cameras found on flagships such as the Galaxy S24 Ultra, Pixel 8 Pro or iPhone 15 Pro Max.

Honor also said it sought to improve the Magic V3's overall camera performance, just like its rivals. Samsung, Xiaomi and Google all improved their foldable phone cameras in their latest book-style phones.

"Compared with our flagship bar phone [Magic 6 Pro], in terms of the photography, we do have some room to improve, especially the total photography performance and as well as the thickness of the module," Cao told CNET in an exclusive interview.

Magic V3's battery and AI

Keeping foldable phones thin continues to pose a challenge for device makers because components such as batteries and processors need to fit into slimmer frames. But those exact features -- battery life and computing power -- matter more now than ever since AI is becoming a larger part of the smartphone experience. 

"In the age of AI, devices require greater computational power and battery performance, all within a slimmer and lighter package," Honor shared with CNET exclusively in an emailed note. "Understand that traditional battery solutions are no longer sufficient to meet these evolving needs."

The silicon carbon batteries packed into Honor's newer phones are a source of pride for the company, which credited Tesla's Model 3 as its inspiration back in 2016. Honor says it spent three years developing the battery of the Magic V3.

Despite slimming down the device, Honor managed to fit a 5,150-mAh silicon carbon battery into the Magic V3, compared with 5,000 mAh in the slightly thicker Magic V2. Honor said it achieved this, at least partially, by increasing the energy density of its battery by 5.74%, while maintaining an average thickness of 2.6 millimeters. 

The Magic V3's 5,510-mAh battery surpasses the latest graphite-based batteries in capacity, the company says, partly driven by higher silicon content of 10.3%. The Magic V3 also comes with what Honor calls an E1 chip that improves battery performance and power management, the company says.

While it's impossible to make a conclusive statement on the Magic V3's battery life without testing it, I reviewed the Magic V2, which uses an older-gen silicon carbon battery. When I performed CNET's streaming video battery drain test, I found that the Magic V2 performed better than the Pixel Fold but worse than the Galaxy Z Fold 5. 

The use of silicon-carbon batteries in mobile phones is an emerging trend that's drawn attention due to its potential advantages over lithium-ion batteries. Those benefits include a lower environmental impact and reduced risk of overheating. However, the long-term reliability of silicon carbon batteries is still being researched.

To that, Honor says it's "confident in the long-term viability of silicon carbon batteries" – even more so since it says it has high internal testing standards, which must be met before the company decides to invest in mass production.

Honor's foldable future

The Magic V3 is the latest addition to Honor's book-style foldable lineup, representing a fine-tuning from its predecessor. The Magic V3 is expected to launch globally at Berlin's IFA tech conference in September, where the Chinese company says it'll highlight the device's new AI capabilities such as those weaved into the user experience and in the camera. 

In terms of Honor's global foldable phones market share, Honor is ranked fifth worldwide in the second quarter of this year, with a 14% market share globally, according to IDC's Will Wong. He points out that despite its technological achievements, Honor still has an uphill climb ahead of it.

"Honor's focus on enhancing both the hardware and software of its foldable products is its key strength and driver," Wong told CNET. "For the brand to go to the next level, more brand awareness and social buzz are needed so that the value of the products could be better known by the consumers."