Every Generation: USB 1.0 To USB-C, How It Evolved & What's Next

As foreign as the idea has become over the years, there once was a time when computers' I/O panels were littered with many different standard connectors for different types of peripherals. Keyboards and mice used PS/2 ports, gamepads had their own port that doubled as the hookup for MIDI musical instruments, and all sorts of other devices leveraged both serial ports and the later parallel ports. Ideally, all of these competing I/O formats would fall to the wayside to make way for a standard that everything could use. The 1996 launch of Universal Serial Bus (commonly USB for short) got the ball rolling on this, but 1998's improved USB 1.1 spec is what really got mass adoption going, thanks in part to Apple phasing out legacy, non-USB ports on new Macs going forward.

In the more than a quarter century since USB started taking over the world, it has evolved, with major revisions up to USB4 and several other sub-revisions in between. Not only have data transfer speeds ballooned over the years, but so has the kind of power that USB can deliver, to the point that USB can now be used to send up to 240 watts to a device. Tweaks to USB have also done wonders for the user experience for owners of devices like smartphones and tablets, as fast charging modes have made it possible to get a device from a dead battery to a decently usable state in minutes. 

USB first hit the market in 1996 with USB 1.0, intending to disrupt a market where the most commonly available I/O solution for anything more robust than a mouse or keyboard was the parallel port at 100 kilobytes per second. The original USB raised the bar by increasing the bandwidth to 12 megabits (1,500 kilobytes) per second while also providing 100 mA of power and adding the ability to attach/detach devices — hot-swapping — without power cycling the computer. Initially, the only connectors supported were USB Type-A — the common full-sized variety wen all thought of as "USB" until Type-C started to take over — and USB Type-B, which was most commonly seen on printers, scanners, external hard drive enclosures, optical drives, and floppy disk drives.

USB 1.0 didn't see much success, but the next revision, 1998's USB 1.1, broke through. It added a low-bandwidth mode of 1.5 megabits (187.5 kilobytes) per second, and this was when device support picked up. In particular, Apple made waves by making the bold choice to remove legacy ports like parallel and serial when it released the iMac G3, instead focusing on USB 1.1. "Apple has publicly declared USB to be the future of all desktop Macs," reads a passage in an October 1998 Macworld article about Apple going all-in on USB, which also noted that PowerBook notebooks were likely to follow suit. "That means bye-bye to the ADB, serial, and SCSI devices we use today–unless you use an adapter, and maybe not even then."

USB leveled up further in 2000 with the launch of USB 2.0, also known as USB High Speed. It promised a transfer rate of 480 megabits (60 megabytes) per second, although bus limitations brought that number down to 280 megabits (35 megabytes) per second; still a significant upgrade over USB 1.1 that increased the top speed by more than 2,300 percent. The power output was also increased to 500 mA. This opened up the possibilities of what USB was capable of a whole lot more. USB flash drives hit the market in 2000 to leverage USB 2.0, for example. USB 2.0 also featured the launch of the USB On-The-Go specification, which allows devices like smartphones — devices that would be considered peripherals if attached to a desktop or notebook computer — to act as a host for the purpose of attaching USB peripherals.

The improvements in USB 2.0 allowed USB to become a legitimate alternative to FireWire, a faster standard that's probably best known for its use in video applications like MiniDV camcorders and being the interface used to sync Apple's original iPod to Macs. Firewire was overall the superior technology at the time, but the gap was closing. In addition, it was during USB 2.0's reign that Micro USB connectors made it to the market in 2007. Until the rise of USB Type-C, Micro USB was commonly used for items like smartphones, supplanting Type-B and Mini USB as the connector on the peripheral side.

Come November 2008, USB evolved into hitting the speeds we've all become used to with the release of USB 3.0. The standard, also known as USBSuperSpeed, is officially capable of transfer speeds up to five gigabits (625 megabytes) per second but generally tops out closer to three gigabits (375 megabytes) per second. The update also increased the power capabilities to 900mA at 5V. For devices with USB Type-A connectors, it's easy to spot if they're USB 3.0 devices, as the inside of the connector is usually colored bright blue. This was followed by additional revisions, as USB 3.1, released in 2013, upped the speed to 10 gigabits per second, with the update also being branded as SuperSpeed+.

The following year, in 2014, the USB Type-C connector was introduced, a reversible connector about the size of Micro USB, which also enhanced the capabilities of USB. 2017's USB 3.2 was only able to increase the transfer speed to 20 gigabits per second because USB Type-C cables allowed transmission of 10 gigabits per second in each direction over two pairs of wire. As the dust settled on the USB 3 revisions, the USB-IF made everything needlessly more complicated, though, with USB 3.0 being renamed USB 3.2 Gen 1 (or SuperSpeed USB 5 Gbps), USB 3.1 being renamed USB 3.2 Gen 2 (or SuperSpeed USB 10 Gbps), and USB 3.2 being renamed USB 3.2 Gen 2x2 (or SuperSpeed USB 20 Gbps). The SuperSpeed branding was dropped by the USB-IF in 2022.

The newest major revision of USB, as of this writing, is the first to break from two-plus decades of a standard naming convention. USB4, which hit the market in 2019, is capable of speeds up to a whopping 40 gigabits per second and, along with updates to the USB Power Delivery standard, raised the maximum wattage that can be transmitted across a USB cable — strictly using USB Type-C now, as USB 4 does — to 240W.  It's based on Intel's Thunderbolt 3 standard, the first Thunderbolt revision to use the USB Type-C connector. Later versions of Thunderbolt (4 and 5) have built on that while being backward compatible. For transparency, USB-IF has split USB4 into both USB4 20 Gbps and USB4 40 Gbps standards, complete with a specific logo for each.

In October 2022, USB-IF announced USB4 Version 2.0, upgrading transfer speeds to 80 Gbps. "For engineers, USB4 is defined by its multi-protocol tunneling that architecturally differentiates it from its predecessors – USB 3.2 and USB 2.0," said Brad Saunders, USB-IF Board Chair and CEO, in the announcement. "This updated technical specification extends USB4 speed and data protocol performance, enabling manufacturers to develop products that can deliver USB 80Gbps in addition to existing USB 40Gbps and USB 20Gbps to end users." In certain use cases, like high-level displays, the standard can also be tweaked to be asymmetrical and allow transfer speeds of 120 Gbps in one direction and 40 Gbps in the other.

Since its launch in 2012, USB Power Delivery has evolved alongside the broader USB spec. It's only leveraged via the USB Type-C connector, and as of this writing, the newest USB PD Revision is 3.1, which was announced in 2021. It was the move to USB-PD 3.1 that allowed USB4 to leverage charging wattage up to 240W via 20V cables rated at 5A. It allows for multiple adjustable voltages, and the power can flow in either direction, including from peripheral to host, when previously, only the opposite was possible.

Revision 3.0 added the sub-spec known as Programmable Power Supply, which allows for communication between devices to adjust voltage and make for more efficient fast charging. PPS is not built into every USB-PD charger, which can greatly confuse consumers. Case in point: If you want to charge your Samsung Galaxy S phone as quickly as possible, as the last several years' worth of flagships use PPS for "Super Fast Charging," you need a charger of the correct wattage with PPS...which Samsung doesn't explain very well at all in its official documentation. You might have a USB Type-C charger with the correct wattage, like a Macbook charger, but because those don't include PPS, you don't get the best possible charging speeds.

The development of USB-PD made it much easier to pick the fastest USB-C charger for your phone. With USB-PD and, to an extent, PPS, the various competing corporate standards like Qualcomm Quick Charge have largely fallen to the wayside.