Thunderbolt symbol

How to read it

Thunderbolt is Intel’s connection standard. Intel says it uses the same oval connector as USB-C, but Thunderbolt certification sets higher minimum performance for cables, computers and accessories, so a USB-C port is not necessarily a Thunderbolt port. Intel’s answer to how to tell is the Thunderbolt icon next to the USB-C port. BGR describes it as a lightning bolt with an arrowhead tip, printed by the port or on the end of the cable. HP says a USB-C port without the icon probably does not support Thunderbolt.

Also searched as: lightning bolt port, Thunderbolt logo.

Generations

The first Thunderbolt port came out in 2011; HP describes it as the product of a partnership between Intel and Apple. Apple’s support guide to Mac ports (September 2026) lists Thunderbolt and Thunderbolt 2 ports on Macs from 2011 to 2017, the same shape as Mini DisplayPort. Thunderbolt 3 moved to the USB-C connector, with a 40 Gbps channel in both directions according to HP; Apple lists Thunderbolt 3 ports on Intel-based MacBook Pros from 2016 to 2020. Intel says Thunderbolt 4 ports also run at 40 Gbps and fit standard USB-C connectors. Intel announced Thunderbolt 5 on 12 September 2023: 80 Gbps in both directions, and up to 120 Gbps for displays with what Intel calls Bandwidth Boost.

The number under the bolt

Intel says every Thunderbolt 4 connector is marked with the Thunderbolt symbol and the number 4. BGR adds that a number printed below the bolt on a cable gives the Thunderbolt generation, and that a bolt with no number generally means a Thunderbolt 3 cable. On the iMac from 2021, Apple prints the Thunderbolt symbol above each of its Thunderbolt / USB 4 ports.

Look-alikes

On Macs from 2011 to 2017, Mini DisplayPort is the one to tell apart. Apple says Thunderbolt and Thunderbolt 2 ports have the same shape as Mini DisplayPort but use different symbols on the cable and port, and Seagate’s support page says the two are easily confused. A lightning bolt without an arrowhead by a USB-A port marks a fast-charging port, BGR says, and the charging bolt is on a battery icon on a screen, not beside a port. The high voltage symbol also ends in an arrowhead, but it is a warning sign, in a yellow triangle. A USB-C port with only speed or power logos is covered under USB-C symbols and logos.