What Does an Ethernet Cable Actually Do

An Ethernet cable carries data between two networked devices using electrical signals over copper wire. It's the wired equivalent of WiFi: same internet, lower latency, more consistent speed, immune to interference. The standard plug is RJ45, the connector that snaps into your router and computer. Inside the cable are eight wires twisted in four pairs, and the way they're arranged determines how fast the cable can carry data.

The way I think about Ethernet is that it's the dependable but unfashionable cousin of WiFi. WiFi is convenient. Ethernet is reliable. Anyone serious about latency (gamers, video editors uploading huge files, traders, anyone running a home server) eventually runs Ethernet to the device that matters and stops fighting WiFi.

What's Actually Inside

Cut open an Ethernet cable and you'll find:

• Eight conductors. Eight color-coded copper wires.
• Twisted in four pairs. Each pair is twisted around itself at a specific rate (different rates per pair to prevent crosstalk).
• Sometimes a shield. Foil or braided shielding around the pairs (shielded twisted pair, STP) or around the whole bundle (foiled twisted pair, FTP). Unshielded (UTP) is more common and cheaper.
• Outer jacket. PVC or LSZH (low-smoke zero-halogen) plastic for protection.

The twisting is genuinely clever engineering. When two wires carry opposing signals (differential signaling) and they're twisted together, electromagnetic interference affects both wires roughly equally and cancels out at the receiver. Without twisting, you'd get electrical noise from every appliance in the house bleeding into the data stream.

The Categories

Cat5

Up to 100 Mbps over 100 meters. Effectively obsolete. If your home has Cat5 in the walls, it's old. New installations don't use it.

Cat5e

Up to 1 Gbps (gigabit). The minimum modern standard. Cheap, widely available, sufficient for most home use cases (streaming, gaming, web browsing) where the bottleneck is your internet plan, not the cable.

Cat6

Up to 1 Gbps over 100 meters, or 10 Gbps over 55 meters. Better shielding and tighter twists than Cat5e. Modest premium over Cat5e. Generally the right default for a new home wire job.

Cat6a (“augmented”)

10 Gbps over the full 100 meters. Real improvement for short to medium runs in offices or homes that actually want 10 GbE. Most enterprise installations now use Cat6a as the default.

Cat7 and Cat7a

10 Gbps over 100 meters with full shielding. Uses GG45 or TERA connectors that aren't fully compatible with the standard RJ45 ecosystem, which limited adoption. Mostly skipped by the industry in favor of Cat6a or Cat8.

Cat8

25 or 40 Gbps over 30 meters. Designed for data center short-run applications. Massive overkill for home use. The shorter distance limit makes it impractical for whole-house wiring.

Speed vs Bandwidth vs Frequency

These three numbers get conflated:

• Speed: Data transfer rate, measured in Mbps or Gbps. What you actually care about.
• Frequency rating: The cable's rated bandwidth in MHz. Cat5e is 100 MHz, Cat6 is 250 MHz, Cat6a is 500 MHz. Higher frequency lets the cable carry more data per pair.
• Length: Affects effective speed. A Cat6 cable that supports 10 Gbps over 55 meters drops to 1 Gbps if you go farther.

For most home networks, your internet speed (300 Mbps to 1 Gbps for typical fiber) is the limiting factor. A Cat5e cable handles 1 Gbps fine. Cat6 gives you headroom. Cat6a is overkill unless you're actually running 10 GbE between devices in your house.

What Ethernet Wins Against WiFi

Three real advantages:

• Latency. Wired typical latency is 1ms or less. WiFi is 5-15ms typical, with occasional 50-200ms spikes. For gaming, video calls, or anything real-time, the difference is felt.
• Consistent speed. WiFi varies with distance, walls, and other devices on the network. Ethernet runs at line speed regardless.
• Interference. WiFi shares spectrum with Bluetooth, microwaves, and your neighbor's WiFi. Ethernet is on copper that nothing else touches.

The disadvantages are obvious. You have to run a physical cable. Phones and tablets don't take Ethernet without an adapter. Aesthetically, cables are uglier than WiFi.

How to Buy Ethernet Cable

For most home use:

• Pre-made cables under 25 feet: Cat6 from any reputable brand. Don't pay extra for premium branding; the spec is the spec.
• In-wall installation: Cat6 or Cat6a, plenum-rated if running through air handling spaces (a code requirement, not optional).
• 10 GbE setups: Cat6a. Don't pay for Cat7 or Cat8 unless you have a specific reason.

Avoid CCA (copper-clad aluminum) cables. They're cheaper but have higher resistance, lower max distance, and don't handle Power-over-Ethernet well. Look for “solid copper” or “100% copper” in the spec.

The Take

For everyone working from home in 2025, running Ethernet to the desk where you actually do video calls and real work is one of the highest-leverage hour-long projects you can do. The latency improvement is meaningful. The consistency is dramatically better. WiFi is great for phones and casual browsing, but for the device that runs your professional life, hardwired beats it on every metric that matters. Cat6 from your router to your desk, fifty bucks at most, half an hour to install.