Download speed is how fast data reaches your device; upload speed is how fast data leaves it. Most home plans give you far more download than upload, which is why calls and backups struggle long before streaming does.
Where download speed matters
Streaming, browsing, downloading games and loading pages all depend on download. This is the big number ISPs advertise.
Where upload speed matters
Video calls, sending files, cloud backup, live-streaming and posting all depend on upload. If Zoom freezes while everything else is fine, upload is your suspect.
How to check yours
Run the speed test and compare the two tiles. A typical home plan might read 200 Mbps down but only 10–20 up — fine for most people, tight for heavy uploaders. See the video-call test for call-specific targets.
