Thunderbolt 3 vs Thunderbolt 4
Both cap at 40 Gbps. Thunderbolt 4 raises the mandatory floor — dual 4K, 32 Gbps PCIe, charging and wake-from-sleep — that Thunderbolt 3 left optional.
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Both run at 40 gigabits per second, so the headline number did not change. What changed is the minimum. Thunderbolt 3 let manufacturers leave a lot optional, so two ports with the same badge could behave very differently. Thunderbolt 4 requires the things people assumed they were getting: two 4K displays rather than one, more bandwidth reserved for storage, charging on at least one port, and waking the computer from a keyboard on a dock. If a Thunderbolt 3 device works for you, there is no speed reason to replace it.
- Verdict:
- Same top speed — 4 makes the optional parts compulsory
Side by side
| Specification | Thunderbolt 3 | Thunderbolt 4 |
|---|---|---|
| Maximum speed | 40 Gbps | 40 Gbps |
| Minimum displays | One 4K | Two 4K or one 8K |
| Minimum PCIe bandwidth | 16 Gbps | 32 Gbps |
| Charging on a port | Optional | Required on at least one |
| Wake from sleep | Optional | Required |
| Longest passive cable | 0.5 m at full speed | 2 m at full speed |
| DMA protection | Optional | Required |
The floor, not the ceiling
This is a specification about minimums. A good Thunderbolt 3 implementation may already do everything Thunderbolt 4 requires. The badge just means you no longer have to check.
Two-metre passive cables
The most practically useful change. Thunderbolt 3 needed an expensive active cable beyond half a metre; Thunderbolt 4 passive cables hold full speed to two metres, which is the difference between a dock on the desk and one behind the monitor.
Security
Thunderbolt exposes PCIe, which historically allowed a malicious device plugged into a locked laptop to read memory directly. Thunderbolt 4 makes the protection against that mandatory rather than optional.
Cables and their length
Any Thunderbolt 4 cable up to two metres carries the full 40 Gbps passively. Under Thunderbolt 3 that required an active cable with electronics in the plug beyond half a metre, which cost considerably more. For desk layout this is the change people notice.
Hubs became possible
Thunderbolt 3 devices daisy-chained in a line. Thunderbolt 4 requires support for hubs, so one port can fan out to several. That is why Thunderbolt 4 docks with multiple downstream ports exist and Thunderbolt 3 equivalents were rare.
USB4 in the same connector
USB4 borrows heavily from Thunderbolt and uses the same plug, with optional speeds of 20 or 40 Gbps. A USB4 port may behave much like Thunderbolt or noticeably less well, since more of it is optional. Thunderbolt certification remains the stricter promise.
Check before you swap. Batteries with similar dimensions are not always interchangeable. Always verify voltage, chemistry and the requirements printed in your device manual before fitting a replacement.
Thunderbolt 3 vs Thunderbolt 4: common questions
What is the difference between Thunderbolt 3 and Thunderbolt 4?
Both run at 40 gigabits per second, so the headline number did not change. What changed is the minimum. Thunderbolt 3 let manufacturers leave a lot optional, so two ports with the same badge could behave very differently. Thunderbolt 4 requires the things people assumed they were getting: two 4K displays rather than one, more bandwidth reserved for storage, charging on at least one port, and waking the computer from a keyboard on a dock. If a Thunderbolt 3 device works for you, there is no speed reason to replace it.
Which should I choose, Thunderbolt 3 or Thunderbolt 4?
Same top speed — 4 makes the optional parts compulsory. Both cap at 40 Gbps. Thunderbolt 4 raises the mandatory floor — dual 4K, 32 Gbps PCIe, charging and wake-from-sleep — that Thunderbolt 3 left optional.
Maximum speed — how do they compare?
Thunderbolt 3: 40 Gbps. Thunderbolt 4: 40 Gbps.