RJ45 Ethernet Pinout Reference
Mobile-friendly RJ45 connector pinout guide for T568A, T568B, straight-through cables, crossover cables and PoE wiring notes.
๐ Quick Rule: For a normal straight-through Ethernet cable, use the same wiring standard on both ends โ usually T568B to T568B or T568A to T568A. Mixing A and B creates a crossover cable.
๐งญ RJ45 plug front view โ contacts facing you, clip away/back
| Pin | T568B Color | Pair | 10/100 Use | Gigabit Use |
|---|
| Pin | T568A Color | Pair | 10/100 Use | Gigabit Use |
|---|
Straight-through cable
End 1T568B
End 2T568B
Also validA to A
Crossover cable
End 1T568A
End 2T568B
Use todayRare
PoE note
Mode AData pairs
Mode BSpare pairs
Modern PoEAuto detect
Search Pin / Color / Function
Filter Group
Quick filters:
| Standard | Pin | Color | Pair | Note |
|---|
๐ RJ45 Quick Reference
Most common wiring
Patch cableT568B-B
AlternativeT568A-A
CrossoverA-B
10/100 Ethernet
TX/RX pairs1-2, 3-6
Spare pairs4-5, 7-8
PoE possibleYes
Gigabit Ethernet
Pairs usedAll 4 pairs
CableCat5e+
Pair twistImportant
๐ Wiring Notes
T568A vs T568B Both are valid. T568B is common in many patch cables, while T568A is also widely accepted. Use one standard consistently.
Keep pair twist close Untwist each pair as little as possible before termination. Too much untwisting can cause crosstalk and failed cable tests.
Do not guess PoE wiring Standard PoE negotiates before power is applied. Passive PoE can damage devices if voltage and pinout are wrong.
Use correct connector type Stranded patch cable and solid installation cable often need different RJ45 plug styles.
RJ45 Ethernet Pinout Reference
This RJ45 pinout reference shows T568A and T568B Ethernet wiring, cable color codes, straight-through cable rules, crossover wiring and PoE pair notes for Cat5e, Cat6 and similar twisted-pair Ethernet cables.
T568A vs T568B color code
The main difference is that the orange and green pairs are swapped. A straight-through cable uses the same standard on both ends. A crossover cable uses T568A on one end and T568B on the other end.
โ Frequently Asked Questions
Both standards work. T568B is very common for patch cables, while T568A is also an official wiring standard. The most important thing is consistency on both ends.
That makes a crossover cable. Modern network devices often support auto MDI-X, but most normal patch cables should still be wired straight-through.
10/100 Ethernet uses pins 1, 2, 3 and 6. Gigabit Ethernet uses all four twisted pairs: pins 1-2, 3-6, 4-5 and 7-8.
With the plug contacts facing you and the clip/latch away from you, pin 1 is on the left and pin 8 is on the right.
Yes. T568A and T568B color codes are used for Cat5e, Cat6 and similar balanced twisted-pair Ethernet cables.
Standard PoE can use data pairs or spare pairs depending on the mode and device. Do not manually inject power unless the device is designed for that PoE type.