The story of the Universal Serial Bus begins in the mid-1990s, when computers were crowded with different ports and every device had its own cable, driver, and ritual. In 1995 a group of companies—Compaq, Digital Equipment Corporation, International Business Machines, Intel, Microsoft, NEC, and Nortel—teamed up to design one universal way to connect things. At Intel, engineer Ajay Bhatt led the chipset work that turned the idea into working hardware. Bhatt joined Intel in 1990 as a senior staff architect on the chipset architecture team in Folsom. He holds one hundred and thirty-two U.S. and international patents, and several others are in various stages of filing. Ajay V. Bhatt (born on 6 September 1957, at Bangalore, Karnataka, India) is an Indian-born American computer architect who defined and developed several widely used technologies, including USB (Universal Serial Bus), AGP (Accelerated Graphics Port), PCI Express, Platform Power Management architecture and various chipset improvements. The first official release of USB 1.0 (Universal Serial Bus), arrived in January 1996 with two data rates, 1.5 megabits per second for low-speed peripherals and 12 megabits per second for full-speed devices, plus the “plug-and-play” setup that made USB feel like magic compared with what came before.
Right from the start, one Universal Serial Bus host port could serve a whole neighborhood of gadgets through hubs—up to 127 devices on a single logical bus. Early motherboards added the rectangular “Type-A” receptacles and peripherals followed quickly: keyboards, mice, printers, scanners, modems, cameras, and storage. The standard supply voltage was five volts, and the earliest ports provided up to 500 milliamps, which is 0.5 ampere, enough to run a low-power device and trickle-charge small batteries. Ports and plugs even picked up color hints that many of us still rely on today: white was commonly seen with Universal Serial Bus 1.x, black with Universal Serial Bus 2.0 “Hi-Speed” at 480 megabits per second, blue with Universal Serial Bus 3.x “SuperSpeed” at 5 gigabits per second, and later teal or purple on some computers for 10 or 20 gigabits per second. These colors are visual cues rather than strict rules, and manufacturers sometimes use red, yellow, or orange to flag high-power or “always-on” charging ports.
The shapes matter in daily life, so it helps to know the approximate sizes. A Standard Type-A plug is about 12.0 millimeters wide and 4.5 millimeters thick. A Mini-B plug used on many older cameras is roughly 7.5 millimeters wide and about 3 millimeters thick. A Micro-B plug that became common on smartphones is about 6.85 millimeters wide and 1.8 millimeters thick. The modern Type-C plug is compact and reversible at roughly 8.4 millimeters wide and 2.4 millimeters thick. Inside the cable, classic Universal Serial Bus 2.0 wiring uses red for +5 volt power, black for ground, green for the D+ data line, and white for the D− data line, with shielding around the data pair. SuperSpeed cables add extra twisted-pair conductors for higher-rate signaling. Type-C adds two “CC” configuration channels and two “SBU” sideband lines to help with orientation, role detection, and advanced modes.
As connector types evolved, so did where they were used. Type-A became the familiar host-side rectangle on computers, televisions, game consoles, car stereos, and chargers. Type-B, the squarer printer-style plug, lived mostly on printers and some scanners and audio interfaces. Mini-A and Mini-B appeared on earlier portable devices before shrinking to Micro-A and Micro-B on smartphones, GPS units, action cameras, and battery banks. A special Micro-B “SuperSpeed” variant with a double-wide shape was common on portable hard drives. Today, Type-C has become the go-to for phones, tablets, laptops, handheld consoles, docks, and many accessories, because one small, reversible connector can deliver both fast data and serious power.
Data speeds stepped up in clear stages. Universal Serial Bus 1.0 and 1.1 ran at 1.5 and 12 megabits per second. Universal Serial Bus 2.0 lifted that to 480 megabits per second. Universal Serial Bus 3.2 brought 5 and 10 gigabits per second, and in a dual-lane mode 20 gigabits per second. Universal Serial Bus 4 built on Thunderbolt technology to reach 20 and 40 gigabits per second, and the latest version of Universal Serial Bus 4 can reach even higher effective rates in certain asymmetric modes. Behind the scenes, cable quality, conductor gauges, and shielding become increasingly important at these speeds; certified Type-C cables carry markings and, for higher currents, an “e-marker” chip that tells devices the cable’s safe capabilities.
Universal Serial Bus was created for data, but once it started carrying five-volt power it was inevitable that charging would follow. Early chargers and ports delivered a fixed five volts at currents like 500 milliamps or 1 ampere. The math is simple and useful in everyday life: watts = volts x amps. A five-watt adapter = 5 volts x 1 ampere. A ten-watt adapter is 5 volts x 2 amperes. A fifteen-watt adapter can be five volts at three amperes or nine volts at 1.67 amperes depending on the protocol in use. A twenty-watt adapter is often five volts at three amperes or nine volts at 2.22 amperes. As time passed, new models with greater voltage options appeared while keeping the same Universal Serial Bus Type-C connector shape, and packaging began to advertise total watts rather than the exact volts and amps inside.
To understand that shift, it helps to know the power standards. Battery Charging 1.2, which is the Battery Charging specification within USB 2.0, allowed dedicated charging ports and charging downstream ports to provide up to about 1.5 amperes at five volts. Universal Serial Bus Power Delivery (USB PD) introduced controlled negotiation so a device and adapter could “handshake” and agree on safe profiles beyond five volts. With Universal Serial Bus Power Delivery 2.0 and 3.0, common fixed levels include five volts, nine volts, fifteen volts, and twenty volts, typically up to three amperes without a special cable and up to five amperes with a properly marked Type-C cable. Programmable Power Supply adds fine-grained voltage steps so a phone or laptop can request, for example, 3.3 to 21 volts in small increments to reduce heat and improve efficiency. The newest Extended Power Range within Universal Serial Bus Power Delivery 3.1, adds higher fixed voltages such as twenty-eight volts, thirty-six volts, and forty-eight volts, supporting power levels like 140 watts, 180 watts, and up to 240 watts when the right five-ampere Type-C cable is used. In simple terms, the market has moved from the original five-volt world to a range that can reach forty-eight volts under Universal Serial Bus Power Delivery 3.1 Extended Power Range, and the device and adapter decide together what to use.
Charger labels you see in stores now cover a wide spread. Five-watt units are typically five volts at one ampere. 5 watt units are five volts at two amperes. 12 watt units are five volts at 2.4 amperes. 15 watt units may be five volts at three amperes or nine volts at 1.67 amperes. 18 watt units often provide nine volts at two amperes or twelve volts at 1.5 amperes. 20 watt units commonly support five volts at three amperes or nine volts at 2.22 amperes. 25 watt to 30 watt units may offer nine volts at 2.77 to 3 amperes or fifteen volts at two amperes. 33 watt units appear with programmable supplies around 11 volts at three amperes. 45 watts is often fifteen volts at three amperes. 65 watts is often twenty volts at 3.25 amperes. 96 watts to 100 watts is commonly twenty volts at five amperes. 140 watts uses twenty-eight volts at five amperes, 180 watts uses thirty-six volts at five amperes, and 240 watts uses forty-eight volts at five amperes. The exact combinations vary with the protocol and the device request, but these examples show how volts times amps tell the story behind the watts printed on the box.
Not every fast charger speaks the same language. In addition to Universal Serial Bus Power Delivery and Battery Charging, there are proprietary protocols marketed under names that promise “quick,” “smart,” “turbo,” or “super” charging. Some of these raise voltage in steps, for example five, nine, or twelve volts; some raise voltage continuously over a range; others keep voltage low, such as five to eleven volts, but push very high current like four, five, or six amperes; and some combine programmable steps with special cables. These approaches can be excellent when the phone and charger understand each other, but they are outside the Universal Serial Bus Implementers Forum standard. If the handshake fails or a device misinterprets a signal, the adapter could deliver a level the device cannot accept, risking battery damage, tripped fuses, burnt traces, or, in extreme cases, catastrophic failure. The handshake—literally the exchange of capability and request messages between power adapter and device using a defined communication channel—is the safety gate that makes modern charging work.
For everyday data use, Universal Serial Bus remains the universal glue. Human Interface Device covers keyboards, mice, and game controllers. Mass Storage Class covers flash drives and many card readers. Audio Class and Video Class carry microphones, speakers, webcams, and capture devices. Network Control Model allows Ethernet adapters. OTG (On-The-Go) lets a phone or small device act as a host and directly connect to a camera, keyboard, or flash drive with the appropriate adapter. Hubs fan the single host port into many logical ports, and modern Type-C hubs and docks can move data while also negotiating power in both directions.
Small devices like earbuds, fitness bands, smart glasses, and watches tend to sip power. Most of them charge at five volts with currents between about 100 milliamps (mA) and one ampere, which is half a watt to five watts. That modest demand is intentional to preserve tiny batteries and control heat. Universal Serial Bus Power Delivery and Programmable Power Supply help here too, because a well-behaved charger can offer exactly what a delicate device asks for rather than blasting out a fixed high voltage.
As more peripherals needed more energy, hubs evolved from simple splitters into powered distribution centers. A powered Universal Serial Bus hub adds its own external power adapter so the upstream host is not overloaded. Inside, the hub routes high-speed data to each downstream port and, separately, allocates power budgets per port. Some hubs share a total pool across all ports, while others provide per-port current limits, electronic fuses, and thermal protection. Power bricks for hubs range widely, from five volts at a few amperes up through twelve, twenty, or even twenty-four volts at several amperes for larger multi-port desktop hubs and docking stations; the hub’s internal regulators then convert that to the five-volt or negotiated Type-C levels each port needs. When choosing a hub, match its data speed to your devices, check that its total wattage and per-port current cover your worst-case mix, prefer certified SuperSpeed or Universal Serial Bus 4-capable designs for high-bandwidth gear, and look for protections like over-current, over-voltage, and short-circuit safeguards.
Because so much power now flows through what looks like the same little port, a few practical habits will keep your devices safe. When you replace a faulty power adapter or borrow one, think in terms of the protocol first and the wattage second. If your phone and adapter both support Universal Serial Bus Power Delivery with Programmable Power Supply, pairing them is ideal. If you are unsure, falling back to a simple five-volt Universal Serial Bus power source at two and a half to three amperes is broadly safe for most devices; it will be slower, but it avoids unexpected voltage steps.
If a device or adapter relies on a proprietary, non-standard fast-charge method and the other side does not, the handshake may not complete correctly; in the worst case the adapter could attempt a voltage your device cannot handle. Good cables matter as much as good chargers. For anything above three amperes or for Extended Power Range levels, use a properly rated Type-C cable with an e-marker chip and avoid damaged or unmarked cords.
Portable and sustainable options have joined the mix as well. Solar Universal Serial Bus chargers and power banks can store or supply energy at five volts and, in more advanced models, negotiate Universal Serial Bus Power Delivery levels when sunlight or stored energy is sufficient. They are convenient for travel and emergencies, but, as with any adapter, matching capabilities and using quality cables keeps charging predictable and safe.
It is worth circling back to color cues because they help in a hurry. The most common wire colors inside a Universal Serial Bus 2.0 cable are red for +5 volt power, black for ground, green for D+ data, and white for D− data. Port bezel colors you see on computers are guidance, not law: white was often used for Universal Serial Bus 1.x, black for Universal Serial Bus 2.0, blue for Universal Serial Bus 3.x at 5 gigabits per second, teal or a bright blue-green for ten gigabits per second, and red, yellow, or orange to flag sleep-charge or high-power ports. Some vendors use purple or other colors to highlight fast-charge features. Treat colors as helpful hints and confirm the actual capabilities when power or speed is critical.
Because most consumers see only watts on packaging, many assume higher wattage means higher voltage. That’s a misconception. Many chargers still deliver 5 V; the “fast-charging” comes from higher amperage or dynamic voltage negotiation under USB Power Delivery protocols. This nuance often goes unnoticed—but matters greatly.
USB is governed by the USB-Implementers-Forum (USB-IF), which defines the standards for voltages, currents, connector types, data speeds, and power negotiation. Manufacturers sometimes create proprietary fast-charging protocols that break from standards. Without the proper “handshake” between charger and device, mismatched voltages or currents may damage batteries, burn circuits, or even cause explosion. The handshake—in which device and adapter communicate using defined protocols—is essential for safe charging.
When you think of Universal Serial Bus today, think of a universal lane that carries both information and energy, balanced by a conversation between the charger and the device. From a single five-volt rail and 500 milliamps in the 1990s, the ecosystem has grown to five, nine, fifteen, twenty, twenty-eight, thirty-six, and forty-eight volts under Universal Serial Bus Power Delivery 3.1 Extended Power Range, with power levels up to 240 watts when the cable and device allow it, and still fully supports simple five-volt accessories. Knowing that watts = volts x amps, and knowing that a safe charge depends on a proper handshake, turns guesswork into confidence. Carry your own charger when you can, choose quality cables, and if you must borrow, defaulting to a known five-volt source is a cautious path.
Universal Serial Bus began as a universal way to transfer data across supporting devices; it has quietly transformed into a universal system for both data and power. With this understanding of names, voltages, watts, speeds, shapes, and what changed behind the scenes, you can pick hubs, chargers, and cables that serve you well for years.
From its humble beginnings in 1996 as a solution to tangled cables and confusing ports, USB has transformed into an essential thread weaving together our digital lives. Each new version carried forward the same spirit: simplicity, speed, and universality. What started as an Intel-led standard is now the invisible handshake between billions of devices worldwide. The story of USB is not just about connectors and data rates—it’s about how technology, when thoughtfully designed, makes life a little easier for everyone, everywhere.
And with a clearer understanding of USB types, plugs, color codes, and charging protocols, you’re better prepared to navigate today’s devices. The next time you upgrade your phone or gadget, you’ll know exactly what to look for—and avoid confusion. USB has quietly shaped the way we use technology, and now you can make the most of it with confidence.