“My internet is 300 Mbps and it still buffers” is one of the most common things people say, and it is usually true. The connection into the building and the connection to the device are two different things, and only the second one determines whether your stream plays.
Why fast connections still buffer
Wi-Fi is a shared, contended medium. Every device on the band takes turns, interference from neighbouring networks reduces throughput, and signal strength falls off sharply through walls, floors and — critically — the metal in the back of a television.
A speed test on a laptop beside the router measures the best case. The streaming stick tucked behind the set, two rooms from the router, on a congested 2.4 GHz channel, may be receiving a fraction of that. It is the same internet connection; it is not the same link.
Things to try before buying anything
Move the stick out from behind the television. The single most effective change, and a short HDMI extension cable costs very little. The back of a television is close to the worst place in a room for a radio.
Use the 5 GHz band. Faster and far less congested than 2.4 GHz, though it carries less well through walls. If your router presents both as one network name, it may be worth separating them so you can be certain which the device is on.
Check what else is on the network. A console downloading a game can saturate a line. Scheduling large downloads overnight is free and often sufficient.
Reconsider the router’s position. Routers end up in hallway cupboards next to the master socket, which is the worst place for coverage. Even moving it onto a shelf in the open helps measurably.
When a cable is the answer
If the device has an Ethernet port, or takes a USB adapter, a cable removes every wireless variable at once: no contention, no interference, no drop-off with distance. For a television in a fixed position it is the most reliable upgrade available, and it is usually cheaper than a mesh system.
Many streaming sticks do not have an Ethernet port, but adapters exist for most of the popular ones and cost little. Check what your device supports before assuming a cable is impossible.
Powerline adapters: the middle option
Where running a cable is impractical, powerline adapters send network traffic through the mains wiring. In a modern building on a single circuit they work well and are far more stable than distant Wi-Fi. In older wiring, or across different circuits, results are poor and inconsistent. Buy from somewhere with a returns policy and test before committing.
Mesh systems
A mesh network helps with coverage — getting a usable signal into a room the router cannot reach. It does not help with contention or with a slow line into the building. If your problem is distance, it is a good answer. If your problem is that six devices are competing, it will disappoint you.
How to know whether it worked
Test on the device itself, in its normal position, before and after. A measurable improvement at the device is the only evidence that matters; an improvement measured on a laptop in a different room tells you nothing about the television.