Measure your download, upload, ping and jitter. There is nothing to install, the test runs in this tab.
Download is how much data you receive per second, upload how much you send. Ping is the time a packet needs for the trip there and back, jitter the variation in that time. For calling and gaming those last two often say more than the number of megabits.
The test talks to a nearby Cloudflare edge. On a fixed line with one close by, a ping under 20 ms is normal. Over mobile internet 30 to 60 ms is normal, and above 100 ms you notice it in video calls.
Not getting the speed from your subscription? Look at your Wi-Fi first. An older router, a connection on 2.4 GHz or a couple of walls in between cost you more than you would think. Measure once over a network cable for comparison: that difference is the gain still left at home.
Usually because of the Wi-Fi between your device and your router, or because someone else in the house is streaming at the same time. A test over a network cable shows what really comes in.
Under 20 ms is fine for gaming and video calls, up to 50 ms you barely notice anything. Above 100 ms people start talking over each other.
The variation in your ping. A steady 30 ms is nicer than an average of 20 ms that keeps spiking to 80.
Because cable and DSL connections reserve most of their capacity for download traffic. On fiber, upload and download are usually close together.
Everything in between counts: your device, your Wi-Fi, your router and only then your provider's line. The weakest link decides the result.