From Cat3 to Cat8: A History of Ethernet Cable

The Cat6A cable you pull through a wall today is the direct descendant of telephone wire — and the "Cat" number system is really a forty-year story of squeezing more signal out of twisted copper pairs. Here's how each generation earned its place, and what that means for which one you should buy.

Before twisted pair: the coax years

Original Ethernet (1980s) ran on thick, rigid coaxial cable — 10BASE5 "thicknet" that you literally tapped with a vampire clamp, then the thinner 10BASE2. It worked, but wiring an office meant a single fragile bus where one bad connector took down everyone. The fix came from an unglamorous place: the phone system.

~1990: 10BASE-T and Cat3 — Ethernet over phone wire

10BASE-T put 10 Mbps Ethernet onto unshielded twisted pair, the same style of cable phones used, terminated in the same 8-position modular jack we now call RJ45. Buildings were already full of it, and the star topology (every desk home-run to a closet) survived faults gracefully. Category 3 was that phone-grade wire, rated to 16 MHz. Twisting the pairs — a trick going back to early telephone lines — cancels interference, and every generation since is essentially better twisting, better materials, tighter tolerances.

1995–2001: Cat5 and Cat5e make 100 Mbps, then gigabit, normal

Cat5 (rated to 100 MHz) carried Fast Ethernet's 100 Mbps and became the default cable of the dot-com office build-out. Cat5e ("enhanced," 2001) tightened crosstalk specs so all four pairs could transmit simultaneously — the requirement for gigabit Ethernet. Cat5e is still a perfectly rational buy for a gigabit-only home; our Cat5e lineup exists for exactly that.

2002–2008: Cat6 and Cat6A chase 10 gigabit

Cat6 (2002, 250 MHz) added an internal spline separating the pairs, and can carry 10 Gbps over short runs (up to ~55 m in clean conditions). Cat6A (2008, 500 MHz) doubled the tested bandwidth and controls "alien crosstalk" between neighboring cables, delivering 10 Gbps a full 100 meters. That's why Cat6A became the standard advice for new construction — the labor of pulling cable costs more than the cable itself. The full comparison lives in our Cat6 vs Cat6A guide; browse Cat6 and Cat6A cables, including armored Cat6A for rodent-prone and outdoor paths.

Cat7: the standard that skipped America

Cat7 (600 MHz, fully shielded per-pair) is real engineering with an odd biography: it was ratified by ISO but never adopted by the US TIA standards body, and it originally specified exotic connectors (GG45, TERA) almost nobody used. In practice, Cat7 cable sold today terminates in ordinary RJ45 plugs and behaves like very well-shielded Cat6A. It has fans — see our Cat7 selection — but it never became an official rung on the TIA ladder.

2016: Cat8, the data center sprinter

Cat8 (2016) is a different animal: 2000 MHz, always shielded, built for 25 or 40 Gbps — but only to 30 meters. It was designed for one job, short hops between servers and switches in a rack, where it undercuts fiber optics on cost and fuss. For a home run to a bedroom it's overkill by design, though the price gap has narrowed enough that plenty of builders future-proof with it anyway. Details in Cat6 vs Cat7 vs Cat8, hardware in our Cat8 collection.

The takeaway from four decades

Each category was built for the network speed of its moment: Cat3 for 10 Mbps, Cat5e for gigabit, Cat6A for 10 gig everywhere, Cat8 for the rack. Buy for the speed your gear will see in the next decade, not the biggest number on the box — and if you're wiring a whole house, start with our home network plan and bulk cable boxes.