With different standards and charging technologies at work, it’s much harder than it should be to figure out what a cable can do. There are a few things that are worth knowing when shopping.
USB standards: The Universal Serial Bus (USB) standard dates from 1996, but has seen many new standards, revisions and plug types in the years since. Instead of going through them all here, we try to highlight what matters.
Connections: Although USB-C is becoming a standard type of connection, you will want cables with connectors that fit your existing devices. Today, it can still mean USB-A, Lightning or even MicroUSB. Remember that the capabilities of any cable are limited to its oldest type of connection.
Data: The data transfer rate is always in megabits per second (Mbps) or gigabits per second (Gbps). You know what speed a cable should be capable of according to the standard:
- USB 2.0 supports 480 Mbps
- USB 3.0 supports 5 Gbps
- USB 3.1 supports 10 Gbps
- USB 3.2 Gen 1 supports 5 Gbps
- USB 3.2 Gen 2 supports 10 Gbps
- USB 3.2 Gen 3 supports 20 Gbps
- USB 4.0 supports 40 Gbps
Power: Although cable manufacturers always specify the maximum charging speed, your device will determine how much power is to be drawn, so it is important to know what standards it supports and combine your cable with the correct power adapter. The charging speed of a cable is measured in watts (W). Sometimes manufacturers will specify specifications on the small print cable. If there is no W in the list, you can calculate it by multiplying the voltage (V) and the current (A), provided they are specified.
USB-A ports are limited to 12 watts. USB-C ports can go up to 240 watts (they used to be limited to 100W), but that depends on the device. For example, USB-C typically delivers 18 watts to a phone. Apple Lightning ports can work with USB-A or USB-C cables.
Thunderbolt was a proprietary interface developed by Intel and Apple, but it is now open for royalty-free use (still certified by Intel). With the Thunderbolt 3, the standard took over the USB-C connector and is capable of data transfer speeds of up to 40 Gbps and can deliver 100 watts of power using the PD standard. Thunderbolt 4 brings various improvements, mainly related to the video signal (support for two 4K monitors or an 8K monitor). It also supports the USB 4 standard and is backward compatible with previous standards. We plan to test Thunderbolt and USB 4 cables over the next few weeks.
The Power Delivery (PD) standard is as close to a common standard as we have. A few manufacturers, such as OnePlus, Oppo and Xiaomi, still have proprietary charging standards. Then there is Qualcomm’s Quick Charge (QC) standard, which was the most popular for phones for many years, although Quick Charge 4+ supports PD. Even PD has a variant called Programmable Power Supply (PPS), which is part of the USB PD 3.0 standard. PPS allows for real-time adjustments to maximize efficiency and charge phones like Samsung’s Galaxy S22 Series by up to 45W instead of the usual 18W.
Cable certification: There are a few different types of cable certification. Once a cable is certified, it usually means that it has been independently tested and conforms to specific standards. It gives you as a buyer peace of mind that your cable performs as the manufacturer claims. Certification can be expensive, so many cable manufacturers avoid it, but that does not necessarily mean that their cables are of poor quality. That USB Implementers Forum (USB-IF) is a non-profit organization dedicated to promoting USB technology. It is run by members such as Apple, Google, HP, Microsoft and Intel, and sets specifications and offers certification. If a cable is certified by USB-IF, it has been tested to ensure that it complies with its standards. Apple has its own Made for iPhone (MFi) certification for Lightning cables.