With various standards and charging technologies at work, figuring out what the cable does is a lot harder than it should be. There are a few things to know when shopping.
USB standard: The Universal Serial Bus (USB) standard dates back to 1996, but in the years since, many new standards, revisions, and connector types have emerged. Instead of going through all of them here, we try to highlight what’s important.
Connector: While USB-C is becoming a standard connection type, you’ll need a cable with a connector that fits your existing device. Today, that could still mean USB-A, Lightning, or even MicroUSB. Remember that any cable’s capabilities are limited to its oldest connection type.
data: Data transfer speeds are always measured in megabits per second (Mbps) or gigabits per second (Gbps). You’ll get an idea of the standard speeds the cable should have:
- 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
strength: While cable manufacturers always list maximum charging rates, your device will determine how much power it consumes, so it’s important to know what standards it supports and to combine your cable with the correct power adapter. The charging rate of the cable is measured in watts (W). Sometimes manufacturers list the specifications of the cable in small print. If W is not listed, you can calculate it by multiplying voltage (V) and current (A), assuming they are listed.
The USB-A port is limited to 12 watts. USB-C ports can go up to 240 watts (they used to be limited to 100 watts), but it depends on the device. For example, USB-C typically delivers 18 watts of power to a phone. Apple’s Lightning port works with a USB-A or USB-C cable.
Thunderbolt is a proprietary interface developed by Intel and Apple, but is now available royalty-free (still certified by Intel). For Thunderbolt 3, the standard features a USB-C connector 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 video signals (support for two 4K monitors or one 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 in the next few weeks.
Power Delivery (PD) standards are as close as we have to common standards. Some manufacturers, like OnePlus, Oppo and Xiaomi, still have proprietary charging standards. Then there’s Qualcomm’s Quick Charge (QC) standard, the most popular phone in 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 real-time adjustments to maximize efficiency and charge phones like the Samsung Galaxy S22 series at up to 45W instead of the usual 18W.
Cable Certification: There are several different types of cable certifications. When a cable is certified, it usually means that it has been independently tested and meets a specific standard. As a buyer, it gives you the peace of mind that your cable will perform to the manufacturer’s requirements. Certification can be expensive, so many cable manufacturers shy away from it, but that doesn’t necessarily mean their cables are of poor quality. The USB Implementers Forum (USB-IF) is a non-profit organization dedicated to advancing USB technology. It is operated by members such as Apple, Google, HP, Microsoft, and Intel to develop specifications and provide certification. If the cable is USB-IF certified, it has been tested to make sure it meets its standards. Apple has its own Made for iPhone (MFi) certification for Lightning cables.