Ethernet cables are labeled by "category" (Cat), and the number tells you the speeds and distances the cable is certified for. They look the same on the outside, so it is easy to overbuy or, worse, use an old cable that bottlenecks a fast connection. Here is what each one does.

Cat5e

The most common home cable. Cat5e is certified for gigabit (1 Gbps) at up to 100 meters and, in practice, handles 2.5GbE and even 5GbE over typical household runs. For most homes on a gigabit plan, Cat5e is genuinely all you need. (Avoid plain Cat5 - it predates gigabit.)

Cat6

Cat6 supports gigabit comfortably and 10 Gbps over shorter runs (about 55 meters). It has tighter specifications and better noise resistance than Cat5e. It is inexpensive and a sensible default for new in-wall wiring you want to last.

Cat6a

Cat6a ("augmented") extends 10 Gbps to the full 100 meters and adds more shielding against interference. It is the practical choice if you are wiring a home for 10GbE or running long cables in electrically noisy environments. It is thicker and a bit stiffer than Cat6.

Cat8

Cat8 supports 25-40 Gbps but only over very short distances (about 30 meters), and it is built for data centers connecting servers and switches. For a home, it is overkill and a waste of money - the speeds it enables require equipment most homes will never own.

Which should you buy?

  • Gigabit internet, normal home: Cat5e or Cat6 - either is fine.
  • Future-proofing in-wall wiring: Cat6 (short runs) or Cat6a (long runs / 10GbE).
  • Multi-gig (2.5G/5G) without rewiring: your existing Cat5e likely already works - see 2.5GbE and multi-gig networking.
  • Home use of Cat8: almost never necessary.

Remember the whole chain

A fast cable cannot exceed the slowest device it connects. Your router, switch, and the device on the other end all need to support the higher speed. For the older background on copper grades, see transmission speeds: Cat5, Cat5e, Cat6, and if you cannot run a cable at all, compare powerline vs MoCA vs Ethernet.