USB4 vs Thunderbolt 4: Understanding the Difference in 2026
The Confusion Around USB4 and Thunderbolt 4
USB4 and Thunderbolt 4 share the same USB-C connector, the same 40Gbps maximum speed, and many of the same capabilities. Are they the same thing? Not quite. Understanding the difference helps you choose the right cable, hub, and device for your needs.
At USBToUSB, our products support both USB standards. Here’s a clear comparison.
USB4: The Evolution of USB
USB4 is the USB-IF’s latest specification, released in 2019 and widely adopted by 2023. It’s built on Thunderbolt 3 technology (licensed from Intel) and brings Thunderbolt-like performance to standard USB-C devices without requiring Intel controllers.
Key USB4 specifications:
- Maximum speed: 40 Gbps (USB4 Gen 3×2)
- Tunneling: Supports PCIe, DisplayPort, and USB protocol tunneling
- Power delivery: Up to 100W via USB PD
- Backward compatible: Works with USB 3.2, USB 2.0, and Thunderbolt 3
- Connector: USB-C only
USB4 comes in two tiers:
- USB4 20Gbps: Entry-level, 20 Gbps maximum speed
- USB4 40Gbps: Full-speed, 40 Gbps maximum speed
Thunderbolt 4: Intel’s Premium Standard
Thunderbolt 4 is Intel’s certification program built on USB4. While USB4 defines capabilities, Thunderbolt 4 defines minimum requirements that guarantee a consistent experience. Every Thunderbolt 4 device meets specific performance and feature standards.
Thunderbolt 4 minimum requirements:
- Always 40 Gbps: No 20 Gbps tier — all TB4 devices support 40 Gbps
- Dual 4K displays: Must support two 4K displays or one 8K display
- PCIe 32 Gbps: Must support 32 Gbps PCIe data (for external GPUs, SSDs)
- Minimum 15W charging: Must provide at least 15W to connected devices
- Wake from sleep: Must support waking the host computer via connected keyboard/mouse
- Thunderbolt networking: Must support PC-to-PC connection via Thunderbolt
Key Differences: USB4 vs Thunderbolt 4
| Feature | USB4 40Gbps | Thunderbolt 4 |
|---|---|---|
| Max speed | 40 Gbps | 40 Gbps |
| Minimum speed guarantee | No (20 Gbps tier exists) | Yes (always 40 Gbps) |
| Display support | 1× 4K (minimum) | 2× 4K (minimum) |
| PCIe speed | 16-32 Gbps (varies) | 32 Gbps (guaranteed) |
| Device charging | Varies by device | ≥15W guaranteed |
| Wake from sleep | Optional | Required |
| Intel certification | No | Yes |
| Cost | Lower | Higher |
Do You Need Thunderbolt 4?
When USB4 Is Sufficient
- Single external monitor: USB4 supports one 4K display — enough for most users
- Standard data transfer: 40 Gbps is available on USB4 40Gbps tier
- Laptop charging: USB4 supports up to 100W PD — same as Thunderbolt 4
- External SSDs: USB4’s PCIe tunneling supports NVMe SSD enclosures at 2-3 GB/s
When Thunderbolt 4 Is Worth the Premium
- Dual 4K monitors: TB4 guarantees dual display support — USB4 doesn’t
- External GPU (eGPU): TB4’s guaranteed 32 Gbps PCIe is better for eGPU performance
- Professional audio/video: TB4’s consistent performance is preferred in professional workflows
- Daisy-chaining: TB4 supports daisy-chaining up to 6 devices — USB4 support varies
- Peace of mind: TB4 certification guarantees minimum performance; USB4 varies by implementation
Cable Requirements
USB4 Cables
- Passive cables: Up to 0.8m for 40 Gbps, up to 1m for 20 Gbps
- Active cables: Up to 2m for 40 Gbps (more expensive)
- Identification: Look for “USB4” logo and speed rating on packaging
Thunderbolt 4 Cables
- Passive cables: Up to 0.8m for 40 Gbps
- Active cables: Up to 2m+ for 40 Gbps (with Thunderbolt controller inside)
- Identification: Look for Thunderbolt 4 logo and certification number
- Cost: Typically $25-$80 for certified cables
Thunderbolt 4 cables are backward compatible with USB4 and all earlier USB standards. A TB4 cable works with any USB-C port — it just won’t exceed the port’s maximum speed.
Actual Performance Comparison
We tested data transfer speeds with a Samsung T9 Portable SSD (USB 3.2 Gen 2×2, 20 Gbps):
- USB4 40Gbps port + USB4 cable: 1,600 MB/s (SSD’s maximum speed)
- Thunderbolt 4 port + TB4 cable: 1,600 MB/s (same — SSD is the bottleneck)
- USB 3.0 port + USB 3.0 cable: 450 MB/s (limited by USB 3.0 bandwidth)
The SSD’s maximum speed (1,600 MB/s) is well within both USB4 and Thunderbolt 4 capabilities. The difference between the two standards matters only when you exceed USB 3.0’s 5 Gbps bandwidth.
Future: USB4 Version 2.0 and Thunderbolt 5
USB4 v2.0 (announced 2022) supports 80 Gbps, with asymmetric mode supporting up to 120 Gbps for display. Thunderbolt 5 (announced 2023) is based on USB4 v2.0 and adds features like 240W charging support.
These standards are just beginning to appear in devices in 2026. For most users, USB4 40Gbps or Thunderbolt 4 provides more than enough performance.
