On the eve of iPhone 6s, we're updating and expanding our history of iPhone series—continuing with the iPhone 4 that changed everything—again!

Steve Jobs returned to the WWDC keynote stage on June 7, 2010. He'd introduced the iPad earlier in the year, and kicked things off with an update on how it, and the App Store had been doing (spoiler: Well!). Then he turned his attention to iPhone, and after recapping everything Apple had done to date, he began on what would come next. It had over 100 new features. It has an all-new design, an all-new camera, and an all new screen resolution. It was hot. It was the iPhone 4

iPhone 4 is the biggest leap since the original iPhone. FaceTime video calling sets a new standard for mobile communication, and our new Retina display is the highest resolution display ever in a phone, with text looking like it does on a fine printed page. We have been dreaming about both of these breakthroughs for decades.

4 times the pixels, 2 times the face

The iPhone 4, codenamed N90/N92 and model iPhone3,1, for the first time, offered significant improvements to the display. Apple went with optical lamination and an in-plane switching (ISP) panel with light-emitting diode (LED) backlighting. It made images look as if they were painted just beneath the glass, and greatly improved the viewing angle. Moreover, instead of matching competing display sizes of the time, they leap-frogged over them. To boost pixel count yet maintain compatibility with existing apps, Apple doubled them both horizontally and vertically, but kept the physical size constant at 3.5-inches. That took them from a resolution of 480x320 to 960x640, and the density from 163ppi to 326ppi. Apple made the argument that, at that point, the pixels disappeared. They called it a Retina display.

It was part of a completely new design, although one that had not been kept a complete surprise (see below). Steve Jobs called it beautiful and it was, something akin to Braun and Leica. Those were aesthetics Apple's senior vice president of design, Jony Ive, held in the highest of esteem. It was flat, chemically-hardened glass (aluminosilicate) front and back, with a stainless steel band running around the sides, and it was 24% thinner than the iPhone 3GS. It would come in black and white, though the former far sooner than the latter.

The cellular radio stayed pretty much the same, at least at first, though Apple did switch from mini to microSIM for the carrier card. Bluetooth stayed the same as well. The Wi-Fi radio went to 802.11 g/b/n, though only on the 2.4Mhz band. The kicker was this — the stainless steel band around the iPhone was the antenna for all these radios. The top left contained Bluetooth, Wi-Fi, and aGPS, and the rest contained UMTS/HSPA. Steve Jobs said it had never been done before. Unfortunately, it hadn't been perfected yet either (see below). Dual mics were also added for noise cancelation and better noise quality.

Again, we had a full model number increase, which meant a full processor increase. In the case it was the custom-designed system-on-a-chip — the Apple A4. It was still an ARM Cortex A8 processor, though clocked higher at 800Mhz, and the same PowerVR SGX535 graphics chip, but it would set the stage for some truly impressive work over the next few years. Storage options stayed the same at 16GB and 32GB, but RAM was increased to 512MB. Like every first generation Retina device, however, it was barely enough to support all those additional pixels. The battery was the sole exception. It jumped to 1420mAh, which meant that, even with Retina, Apple actually managed to increase useful battery life as well.

In addition to the previous accelerometer and compass, Apple added a 3-axis gyroscope to the iPhone 4, with pitch, roll, and yaw, as well as rotation around gravity. Working together they provided 6-axis motion detection. It was a huge leap forward when it came to precision control, especially for gaming.

Apple took the iPhone 4's rear camera to 5 megapixels and 720p video, but at the same 1.75 micro pixel size, and added a backside illuminated sensor (BSI) and LED flash. There was, however, one more thing.

For the first time, Apple also added a front camera, VGA resolution. While it was a boon to the profile pics and "selfies" that were growing in popularity, it also allowed Apple to launch FaceTime video calling.

Price once again stayed the same, $199 and $299 on contract.

The best iPhone ever. Again.

The iPhone 4 launched on June 15, 2010. It would hit 88 countries and 185 carriers by the end of the year. Apple also launched iOS 4 along with it. Despite an initial rollout of only 5 countries, and considerable supply constraint, Apple still sold 1.7 million that first weekend.

Steve Jobs said, via Apple:

This is the most successful product launch in Apple's history. Even so, we apologize to those customers who were turned away because we did not have enough supply.

AT&T let anyone within 6 months of their upgrade window qualify for full subsidy pricing — likely because they had an inkling what was coming — and even though the iPhone 4 provided far more hardware features than the iPhone 3GS, it was again aimed primarily at iPhone 3G owners and new customers, not the smaller niche of year-over-year upgrades. Sascha Segan for PC Mag

The iPhone 4 is the best iPhone ever. That's for certain. It's the best media playing phone on the market, a terrific camera phone, and a truly awesome game-playing phone. It easily makes the cut for our list of The 10 Best Touch-Screen Phones. It's not the best phone-calling phone, but we've gone well beyond the era when everyone bought handheld, networked computers primarily for making long voice calls.

Joshua Topolsky for Engadget:

We're not going to beat around the bush -- in our approximation, the iPhone 4 is the best smartphone on the market right now. The combination of gorgeous new hardware, that amazing display, upgraded cameras, and major improvements to the operating system make this an extremely formidable package. Yes, there are still pain points that we want to see Apple fix, and yes, there are some amazing alternatives to the iPhone 4 out there. But when it comes to the total package -- fit and finish in both software and hardware, performance, app selection, and all of the little details that make a device like this what it is -- we think it's the cream of the current crop.

Yours truly for iMore:

An impressive new design, amazing new display, key features like multitasking, and an attempt to mainstream video calls, along with hundreds of other little improvements combine together to make this a substantial upgrade and clearly the best iPhone ever. (Given the success of previous iPhones, that's no faint praise).

With the iPhone 4, Apple for the first time began pushing the hardware well past the software.

Leaps... and stumbles

As innovative and exciting as the iPhone 4 was, it was also a painful year in many ways for Apple and for the product line, starting well before the launch. On April 19, 2010, it was revealed that an iPhone 4 prototype had been separated from an Apple engineer at a Redwood City bar. That prototype eventually made its way online, resulting in Apple's biggest product leak ever. While other sites got photos, the site that got the phone was Gizmodo.

The fallout wouldn't just result in less of a surprise and cranky comments from Steve Jobs at WWDC and AllThingsD, it would result in a police investigation, and considerable changes at and repercussions for both Apple and Gizmodo.

The color white also provided Apple with considerable challenges. They had to prevent UV rays from yellowing it over time, and they had to prevent the opacity of the paint from interfering with the internal sensors. That took longer than they anticipated. Short term it meant the white iPhone 4 would not ship on time. On June 23, the following statement was released by Apple:

White models of Apple's new iPhone® 4 have proven more challenging to manufacture than expected, and as a result they will not be available until the second half of July. The availability of the more popular iPhone 4 black models is not affected.

It would take until April 28, 2011 to hit the shelves. Phil Schiller, senior vice president of worldwide product marketing, Apple:

The white iPhone 4 has finally arrived and it's beautiful. We appreciate everyone who has waited patiently while we've worked to get every detail right.

Apple's new, external antenna design, for all it's benefits when a strong signal area, turned out to very literally have a weak spot when the signal was weak. If you put your finger on the band at the bottom left, you could detune it and kill the network connection dead. This might have been a great data pause/play button if you were ever downloading NSFW content and the boss walked in, but it caused a very real problem for people living in regions with poor reception. And with AT&T in the U.S., that wasn't insignificant.

Apple at first tried to show that any mobile phone, if enough surface area was covered, could suffer from signal strength attenuation. That was true but also beside the point. Apple also claimed they discovered an error in how iOS was reporting signal strength in general. On July 2, an open letter was published by Apple:

Upon investigation, we were stunned to find that the formula we use to calculate how many bars of signal strength to display is totally wrong. Our formula, in many instances, mistakenly displays 2 more bars than it should for a given signal strength. For example, we sometimes display 4 bars when we should be displaying as few as 2 bars. Users observing a drop of several bars when they grip their iPhone in a certain way are most likely in an area with very weak signal strength, but they don't know it because we are erroneously displaying 4 or 5 bars. Their big drop in bars is because their high bars were never real in the first place.

To fix this, we are adopting AT&T's recently recommended formula for calculating how many bars to display for a given signal strength. The real signal strength remains the same, but the iPhone's bars will report it far more accurately, providing users a much better indication of the reception they will get in a given area. We are also making bars 1, 2 and 3 a bit taller so they will be easier to see.

It wasn't enough. On July 16, Apple held a press conference to address the ongoing issue and, in addition to again conflating detuning with attenuation, offered free bumpers to anyone suffering from the problem. Apple also granted an unprecedented look inside their multimillion dollar antenna design and testing center. They'd later redesign the antenna and reduce, and then eliminate the problem.

We wouldn't have to wait a full year for a completely new iPhone generation to get the redesigned antenna, however. We only had to wait some six months, at least for the announcement.

On January 10, 2011 Apple's then-COO Tim Cook took the stage at another, separate event and announced the iPhone would, at long last, come to Verizon. It launched on February 10, and included a new antenna array that not only minimized detuning but supported CDMA and EVDO Rev A networking. EVDO Rev A was nowhere nearly as fast as GSM HSPA, nor could it handle simultaneous voice and data, but thanks to Verizon's network, it greatly increased the reach and customer experience in the U.S.

Combined with the white iPhone 4 shipping, it let Apple leave that year on a considerable high.

How to make a competing phone

Four Years Later

The competitive market saw BlackBerry and Microsoft continue to struggle in the dark, Palm continue to struggle in the light, and Google's Android continue to come on like a freight train. The iPhone 3G was gone, the iPhone 3GS remained, and the iPhone 4 once again took Apple to greater numbers than ever before. Nothing, however, could prepare the world for what would happen next...

More on the history of the iPhone