"My internet is 500 Mbit/s, so why does my TV buffer?" The speed your ISP sells you is measured to the router. Your TV only gets what reaches it inside your home. Here is a reproducible way to measure that.
What you need
- A computer connected to the router by Ethernet (the "server")
- A second device in the same spot as your TV: a laptop, an Android TV box with Termux, or a phone (the "client")
-
iperf3(free, open source)
1. Install iperf3
# Debian/Ubuntu
sudo apt install iperf3
# macOS (Homebrew)
brew install iperf3
# Windows: download the official build from iperf.fr
2. Start the server on the wired machine
iperf3 -s
3. Run the client from where the TV is
# 30-second test, server -> client (the direction a stream flows)
iperf3 -c <server-ip> -t 30 -R
4. Read the result
Look at the receiver bitrate and the retransmits (Retr). As a rough guide for a single stream:
| Quality | Typical requirement |
|---|---|
| HD (1080p) | ~15–20 Mbit/s |
| 4K | ~25–30 Mbit/s |
Leave headroom – other devices in the home share the same network.
5. Compare Wi-Fi and Ethernet
Run the same test twice: once on Wi-Fi and once with a cable or powerline adapter. If Wi-Fi is far below the cabled result, or shows many retransmits, the bottleneck is your Wi-Fi, not your ISP.
6. Things that usually fix it
- Move the router to a central, elevated spot, away from metal cabinets
- Use the 5 GHz band when the TV is in the same room as the router
- Add a mesh node or a powerline adapter for distant rooms
- Use Ethernet for the TV or streaming box whenever possible
7. Test at peak time
Repeat the test on a Friday evening. If your LAN results are fine but streams still buffer only at peak hours, the bottleneck is upstream (your ISP or the streaming service), not your home network.
Disclosure: I work with IPTV Nordic, a Nordic streaming service. More streaming guides (in Swedish) are at iptvnordic.store.
