Everything you need to know about USB Standards, Speeds and Port Types

USB or ‘Universal Serial Bus’ is one of the oldest and most popular interfaces today. While it was initially introduced as a computer port, it is now seen on almost every single piece of tech including smartphones, gaming consoles, cameras, etc. in some form or the other. The main objective of making USB was to provide a standardized connection of peripherals to PCs. Today, USB stands true to its name, thanks to the wide acceptance and a broad variety of supported hardware and software. Let’s take a look at the brief history of USB as well as list all the various types of connectors and standards.

How did USB come into existence?

The development of USB began in 1994 with the aim to make a single connector that could basically replace a number of connectors seen on PCs. The purpose of USB was also to bring a more simple software configuration of all devices that could connect through USB, to allow faster data rates for external devices, and to address the usability issues of existing interfaces. USB was not a one-man invention though. It was a group effort that included a total of seven companies namely Compaq, DEC, IBM, Intel, Microsoft, NEC, and Nortel. The team led by Ajay Bhatt worked on the standard at Intel and the first integrated circuits supporting USB were produced in 1995.

USB 1.0

The first specification called USB 1.0 made its debut in January 1996 offering data transfer speeds of 1.5 Mbps (Low Speed) and 12 Mbps (Full Speed). The decision to add two-speed configurations was taken so that it could support both high-speed devices like printers and disk drives as well as low-cost peripherals like keyboards and mice. USB 1.1 was actually the first widely used specification as it made its first appearance on the Apple iMac in September 1998. A variety of manufacturers followed Apple and started producing legacy-free PCs with USB ports.

USB 2.0 and USB 3.0

In April 2000, the USB 2.0 specification was announced after getting consent from the USB Implementers Forum (USB-IF). It was made available in 2001. Hewlett-Packard, Intel, Lucent Technologies (Nokia), NEC, and Philips pushed for higher data transfer rates, where the new standard brought speeds of up 480 Mbps. We then saw USB 3.0 publish on 12 November 2008 to further increase data transfer speeds to up to 5 Gbps, which was also called SuperSpeed. The new standard also focused on decreasing power consumption, increasing power output, and provided backward compatibility with USB 2.0. The first set of devices featuring USB 3.0 came out in January 2010.

USB 3.1 Gen 1 and Gen 2

The USB 3.1 specification was first announced in July 2013 and this is where things started to get a bit confusing. It was launched in two versions, USB 3.1 Gen 1 and USB 3.1 Gen 2. While the first one retained USB 3.0’s 5 Gbps (SuperSpeed) transfer mode, Gen 2 introduced SuperSpeed+ transfer mode with maximum data signaling rate to 10 Gbps. In September 2017, the USB 3.2 specification was published which yet again brought a change in the naming scheme. USB 3.2 Gen 1 was actually the same as USB 3.1 Gen 1, USB 3.2 Gen 2 was the new USB 3.1 Gen 2 and USB 3.2 Gen 2×2 was the newest and fastest offering speeds at up to 20Gbps.


The latest standard is called USB 4 which was announced last year by the USB Promoter Group. The new USB 4 standard will offer 40 Gbps maximum speed similar as well as compatible with Thunderbolt 3, DisplayPort Alt Mode 2.0, and better resource allocation for video. Devices with USB 4 are expected to arrive by next year. Additionally, USB 4 will also be optimized for Thunderbolt 4, which was announced at the beginning of this year.


Unlike the USB standard which prides itself upon universality and acceptance as a “standard”, Thunderbolt is a standard that is developed and licensed by Intel. It doesn’t form part of the history of USB as it does not succeed or precede any USB standard, but it bears mentioning just to clear up any confusion. It is a cross-platform data and power transfer standard, but devices need to be certified for use with this standard. The protocol is often found in laptops and PCs and can be used to connect DisplayPort-compatible devices including external monitors as well as PCI Express (PCIe) peripherals including external graphics cards, hard drives, Wi-Fi or Ethernet connectors, over a USB-C port. The current generation of the protocol – Thunderbolt 3 – supports upstream or downstream bandwidths of up to 40Gbps and serves as the basis for USB 4 specifications. The new Thunderbolt 4 standard is expected to bring additional features over Thunderbolt 3.

USB Connectors and Ports

Before we talk about the various types of USB ports and connectors, let’s talk about the difference between the connector and the port. The port is what you have on your device like a smartphone or PC. It is where you plug in a cable or external device, say a thumb drive. The connector is usually seen on the cable itself that plugs into the port. This means you need a matching port for the connector to plug-in. One also needs to understand that a USB standard relies on the connector and port combination. The newer the port/connector, the newer standard it can usually adopt. Having said that, there are cases where manufacturers implement older USB standards to newer ports/connectors to save costs.

usb ports and standards

Image credits: Wikipedia


The very first flat, rectangular connector is still a common sight on devices like PCs, gaming consoles, TVs, etc. It has served well over the years to transfer data and power efficiently and currently offers the USB 3.2 standard. It has seen upgrades in terms of bus lanes and transfer speeds but overall, the design has remained the same.


USB-B is not that common anymore but you might still see this port on large devices, like scanners or printers as well as on certain audio devices. The port has a squarish look while the other side of the cable would most likely have a USB-A port to connect to a PC.


Now, this was a smaller port but it was based on the USB-B port. It was primarily used for charging and transferring data from devices like cameras and MP3 players, although it isn’t very common anymore. There was a Type-A version as well, but both were soon taken over by a smaller version, the micro-USB.


Micro-USB was one of the most popular USB ports thanks to the adoption in smartphones, tablets, and a variety of other portable gadgets and accessories. While it is being phased out in favor of the USB-C port, you can still find a variety of devices that still rely on the port.


This is the current standard and is finally the first USB port that you can plug correctly in one go as it is reversible. Apart from offering faster data and power delivery speeds, it also offers display connectivity making it the perfect universal port. You can see this port on almost every new-age device from smartphones, laptops, tablets, headphones, and so on. It has the potential to deliver 100w of power, making it suitable for charging a wide range of devices including laptops. This is also the new-age connector for the Thunderbolt standard offering 40 Gbit/s and 4K video output.

Power Delivery

Now apart from transferring data, USB has been used for charging devices as well. Up until USB 3.1, the maximum power one could get was 5V/900mA over USB Type-A. This was followed by USB Fast Charge, a new standard that increased speeds to 5V/1.5A. These charging speeds were suitable for small devices and certain smartphones as well. However, with the improvements in technology and a requirement for much higher battery charging speeds, the USB Implementers Forum introduced USB Power Delivery. It has become an industry-standard open specification that can provide high-speed charging with a variable voltage of up to 20V and 5A at 100W depending on the device. This can be used to charge anything from smartphones to laptops using the USB-C connector on both ends.

The USB port is finally living up to its name. After going through various revisions over the year in terms of hardware and software, we can now say that the USB (thanks to the Type-C) is indeed a universally accepted standard. Not only can it deliver data and power at fast speeds, one can even use it to input or output video. No wonder even Apple is slowly moving away and replacing its Lightning connector with USB Type-C.

The post Everything you need to know about USB Standards, Speeds and Port Types appeared first on xda-developers.

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