fivem-player-list

Simple website that will dipslay you all players connected to selected sever. It is available here: https://igorovh.github.io/fivem-player-list/

It is using FiveM endpoint, which is used in their UI:

https://servers-frontend.fivem.net/api/servers/single/serverId

How to get Server ID?

Server Browser

Visit FiveM Server Browser and click on chosen server.
After that look into the URL and copy last fragment, which is Server ID. Example:
https://servers.fivem.net/servers/detail/vp4rxq -> vp4rxq

Client

Find server in FiveM client and click on it.
In the right side you will have "join URL", in which last fragment is Server ID. Example: cfx.re/join/vp4rxq -> vp4rxq