With different standards and charging technologies at work, it’s much harder than it should be to determine what a cable can do. There are a few things worth knowing when shopping.
USB standards: The Universal Serial Bus (USB) standard dates back to 1996, but has seen many new standards, revisions, and connector types in the years since. Instead of going through them all here, we try to highlight what is important.
connectors: Although USB-C is becoming the standard connection type, you want cables with connectors that match your existing devices. Today, that can still mean USB-A, Lightning, or even MicroUSB. Note that the capabilities of each cable are limited to its oldest connection type.
Data: Data transfer speed is always in megabits per second (Mbps) or gigabits per second (Gbps). You will know the speed that the 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 a maximum charge rate, your device will determine how much power it will use, so it’s important to know what standards it supports and match your cable with the correct power adapter. The charging speed of the cable is measured in watts (W). Sometimes manufacturers will list the specifications on the cable in fine print. If W is not listed, you can calculate it by multiplying the voltage (V) and current (A), assuming they are listed.
USB-A ports are limited to 12 watts. USB-C ports can reach up to 240 watts (they used to be limited to 100W), but it depends on the device. For example, USB-C typically delivers 18 watts to a phone. Apple’s Lightning ports can work with USB-A or USB-C cables.
Thunderbolt was a proprietary interface developed by Intel and Apple, but is now open for free use (and still certified by Intel). Along with Thunderbolt 3, the standard has adopted the USB-C connector and is capable of data transfer rates 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 displays or an 8K screen). It also supports the USB 4 standard and is backward compatible. We plan to test the Thunderbolt and USB 4 cables in the next few weeks.
The Power Delivery (PD) standard is as close to a common standard as we get. A few manufacturers, such as OnePlus, Oppo and Xiaomi, still have proprietary charging standards. Then there’s Qualcomm’s Quick Charge (QC) standard, which has been 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 enables real-time adjustments to maximize efficiency and charge phones such as the Samsung Galaxy S22 at up to 45W instead of the usual 18W.
Cable certification: There are several different types of cable certification. When a cable is certified, it usually means that it has been independently tested and conforms to specific standards. This gives you, as the customer, peace of mind that your cable is performing as the manufacturer claims. Certification can be expensive, so many cable manufacturers avoid it, but this does not necessarily mean that their cables are of poor quality. The USB Implementers Forum (USB-IF) is a non-profit organization dedicated to the advancement of USB technology. Led by members such as Apple, Google, HP, Microsoft and Intel, it 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.