568A vs 568B: Which Wiring Standard Should You Use
568A and 568B are two wiring standards from TIA/EIA that define how eight wires in an RJ45 connector map to color-coded pairs for Ethernet. Both support Cat5, Cat5e, Cat6, and higher, providing 10/100/1000 Mbps depending on cable quality and use of all four pairs. They differ only in pinout arrangement: 568A sequences wire pairs to green and orange, while 568B sequences them to orange and brown. Functionally, performance is identical when each end follows the same standard; cross-over behavior is handled by devices or cabling rather than by the standard choice itself.
Why Two Standards Exist: History and Origins
568A was originally published as the Telecommunications Industry Association standard for commercial building cabling, emphasizing a standardized color code tied to pair position. 568B gained adoption largely because early vendors and installers favored its orange-based pair ordering, which aligned with some existing patch panel and jack conventions. Neither was designed to improve electrical performance; they exist primarily to ensure interoperability and simplify troubleshooting across diverse installations.
Pinout Comparison at a Glance
| PIN | 568A COLOR | 568B COLOR | USE |
|---|---|---|---|
| 1 | White/Green | White/Orange | Tx+ or Rx+ |
| 2 | Green | Orange | Tx− or Rx− |
| 3 | White/Orange | White/Green | Rx+ or Tx+ |
| 4 | Blue | Blue | NC or Ri |
| 5 | White/Blue | White/Blue | NC or Ri |
| 6 | Orange | Green | Rx− or Tx− |
| 7 | White/Brown | White/Brown | Unused or PoE+ |
| 8 | Brown | Brown | Unused or PoE+ |
How They Work in Real Networks
For straight-through Ethernet, both standards deliver identical signal integrity when each end is terminated consistently. Devices use pairs 1,2 and 3,6 for 10/100/1000BASE-T, while pins 4,5 and 7,8 are typically unused unless supporting Power over Ethernet (PoE) or legacy equipment. Modern network interfaces auto-negotiate and handle any required crossover, making the choice of standard largely a matter of compatibility and documentation rather than performance.
When to Choose 568A vs 568B
- Use 568A when backward compatibility with legacy systems or adherence to original building standards is required.
- Use 568B when aligning with common vendor defaults, existing patch panels, or simplifying matching with preinstalled cables.
- Use crossover cables or auto-MDI/MDIX devices when connecting like devices (e.g., switch to switch) regardless of standard.
- Maintain consistency within a single installation to avoid confusion and simplify troubleshooting.
Practical Best Practices
Document the standard used on every patch panel, outlet, and cable run. Label both ends clearly with the chosen standard and termination date. For new builds, pick one standard organization-wide and train installers to follow it precisely. When expanding or repairing, match the existing standard unless a deliberate migration plan is in place. Use cable testers or certifiers to verify pinout, pair twists, and performance after termination.
FAQs
Can I mix 568A and 568B in one installation?
Yes, but only if each cable run is consistent end-to-end and clearly labeled. Mixing standards without discipline leads to wiring errors and hard-to-diagnose faults.
Does one standard perform better than the other?
No. Electrical performance depends on cable quality, termination quality, and length, not on whether the termination follows 568A or 568B.
Does PoE care which standard I use?
PoE works on either standard because it uses spare pairs (4,5 and 7,8) or, with newer implementations, all pairs simultaneously. Ensure your cabling and connectors support the required PoE mode and current levels.
Are 568A and 568B the only standards?
TIA/EIA-568 defines these primary standards; other regional or proprietary schemes exist but are uncommon in mainstream Ethernet cabling.