UK users can use the Ofcom checker to Run a speed test and then click 'details' to see estimated upload and download speed.
If you have an upload speed of ~500 Kbps (0.5 Mbps) or less, you may want to use voice only, especially
if joining a group call (that is, turning off your video).
Standard broadband (ADSL) normally has a maximum upload speed of around 1 Mbps and would be better suited to either one to one video calls, or audio only in a group call.
Fibre services provide greater bandwidth so can handle more traffic and is better suited to group video calls, upload speed