With different standards and charging technologies at play, figuring out what a cable can do is harder than it should be. There are a few things to know when making a purchase.
USB Standard: The Universal Serial Bus (USB) standard dates back to 1996 but has seen many new standards, revisions, and connector types in the years since. Rather than discuss them all here, we try to highlight the ones that matter.
Connectors: While USB-C is mercifully becoming a standard connection type, you'll want cables with connectors that fit your existing devices. Today, that can still mean USB-A, Lightning, or even microUSB. Remember that the capabilities of any cable are limited to its oldest connection type.
data: Data transfer speeds are always in megabits per second (Mbps) or gigabits per second (Gbps). You will know what speed a cable should be capable of according to the standard:
- USB 2.0 supports 480Mbps
- Supports USB 3.0 5 Gbps
- Supports USB 3.1 10 Gbps
- USB 3.2 Gen 1 supports 5 Gbps
- Supports USB 3.2 Gen 2 10 Gbps
- USB 3.2 Gen 3 supports 20 Gbps
- USB 4.0 supports 40 Gbps
Power: While cable manufacturers always list a maximum charging rate, your device will determine how much power to draw, so it's important to know what standards it supports and pair your cable with the right power adapter. The charging rate of a cable is measured in watts (W). Sometimes manufacturers will list specifications in small print on the cable. If there is no W listed, you can calculate it by multiplying the voltage (V) and current (A), assuming they are listed.
Basic USB-C cables are passive and can only handle up to 60 watts. Cables that can carry 100 watts or more, sometimes described as active, must have E-marker chips that identify the cable and its capabilities.
The Power Delivery (PD) standard is as close as we have to a common standard. Some manufacturers like OnePlus, Oppo, and Xiaomi still have proprietary charging standards. Then there's Qualcomm's Quick Charge (QC) standard, which was the most popular for phones for many years, although Quick Charge 4+ supports PD. PD even has a version 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 the phone Samsung's Galaxy S22 range Up to 45 watts instead of the usual 18. The latest addition to the PD is Extended Power Range (EPR), which allows USB-C cables to deliver up to 240 watts (they used to be limited to 100 watts).
Thunderbolt was a proprietary interface developed by Intel and Apple, but is now open for royalty-free use (still certified by Intel). With Thunderbolt 3, the standard adopted the USB-C connector and is capable of data transfer speeds up to 40 Gbps and can provide 100 watts of power using the PD standard. Thunderbolt 4 brings various improvements mostly related to video signals (support for two 4K displays or 8K displays). It also supports the USB 4 standard and is backward compatible with previous standards.
Cable Certification: There are a few types of cable certification. When a cable is certified, it usually means that it has been independently tested and conforms to specific standards. As a buyer this gives you peace of mind that your cable works as claimed by the manufacturer. Certification can be expensive, so many cable manufacturers avoid it, but it doesn't mean their cables are poor quality. USB Implementers Forum (USB-IF) is a non-profit organization dedicated to advancing USB technology. Run by members such as Apple, Google, HP, Microsoft, and Intel, it sets specifications and provides certification. If a cable is USB-IF certified, it has been tested to ensure that it complies with its standards. Apple has its own Made for iPhone (MFi) certification for the Lightning cable. Intel certifies Thunderbolt cables. Certified cables usually have the corresponding logo on the connector. (For example, a Thunderbolt cable contains a Lightning bolt.)