Both Wi-Fi and Ethernet move IP packets. They behave very differently at the physical layer, and those differences are why your video call freezes when someone else in the house starts streaming, while a wired laptop in the same room sails through.
The fundamental difference
Ethernet is full-duplex: every device has its own pair of wires, and sending + receiving happen on separate pairs simultaneously. Wi-Fi is half-duplex: everyone on the same channel shares one piece of air. At any instant, exactly one device on that channel can be transmitting; everyone else listens.
Worse, devices can't tell if their transmission collided with someone else's — the receiver might pick up garbage, the sender doesn't know. So Wi-Fi uses CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance): listen before talking, random back-off, hope nobody else picked the same slot. Adds latency, even on an idle channel.
What adds latency on Wi-Fi
- Channel contention. Every other device on the network — phones, smartwatches, smart bulbs — competes for the same air. More devices = more back-off waiting before each transmission.
- Interference. Microwaves, Bluetooth, the neighbour's Wi-Fi, even poorly-shielded USB 3.0 cables. Each one corrupts a packet → retransmission → multi-ms delay.
- Distance and signal strength. Lower signal = the radio negotiates a slower modulation. Same packet takes longer to fly through the air.
- Retransmissions. A failed packet must be re-sent, and the retransmit starts at the back of the queue. Tail latency under load is dominated by these.
- Sleep modes. Battery-powered devices wake periodically. Your phone isn't always listening; it negotiates DTIM intervals with the AP. Adds millisecond delays on incoming traffic.
What that looks like in numbers
- Ethernet to your router: 0.1–0.5 ms, ~0 jitter, 0% loss on a healthy link.
- Wi-Fi 5 (802.11ac) idle: 1–3 ms, <1 ms jitter, ~0% loss when there are no other devices.
- Wi-Fi 5 contested (kids streaming, smart-home gossiping): 5–30 ms, 5–10 ms jitter, occasional 1–2% loss.
- Wi-Fi at the edge of range: 50–200 ms, double-digit jitter, painful packet loss.
For most browsing, none of this is noticeable. For gaming, video conferencing, and live-streaming, all of it is.
When Wi-Fi is "good enough"
- Browsing, streaming pre-buffered video, scrolling social media: Wi-Fi is fine.
- VoIP calls: Wi-Fi is fine if the signal is decent and you're not contending hard.
- Cloud-saved gaming or asynchronous multiplayer: Wi-Fi is fine.
When you want Ethernet
- Competitive online gaming (FPS, fighters, MOBAs).
- Hosting a server or game lobby.
- Latency-sensitive remote work (RDP, live-coding pair work).
- 4K streaming on flaky Wi-Fi.
- Big bulk file transfers — sustained throughput is higher and more predictable.
What to do when Ethernet isn't an option
- Modern Wi-Fi standards help. Wi-Fi 6 / 6E / 7 add OFDMA + MU-MIMO, which slice the air more finely so contention hurts less.
- 5 GHz band beats 2.4 GHz for latency and crowd-tolerance — fewer devices, more non-overlapping channels.
- Mesh nodes with a wired backhaul between them keep good signal in every room. Mesh with a wireless backhaul roughly doubles the latency cost.
- QoS / WMM prioritises latency-sensitive traffic (voice, gaming) over bulk downloads.
- Powerline / MoCA use existing electrical / coax wiring as the backhaul. Faster + more predictable than wireless for most home situations.
If you're trying to diagnose latency right now, the home page shows your public IP — but the actual ping you care about lives between your device and the game server. Try a traceroute to the destination and see where the latency jumps. The first hop is almost always Wi-Fi if you're wireless; if that hop is slow, fix Wi-Fi before doing anything else.