The visitor IP address shows in the first of the list in the request header
This may be less useful for tracking than you’d expect because
- VPN may assign different IP on each visit
- ISP may assign different IP on each visit
- CGNAT (ISP) may assign same IP across many visitors
- bots on shared hosting may be assigned the same IP across many bots
If you mean Glitch’s container limit, I don’t think this is possible, as Glitch’s limit is imposed before the app receives the request. You could keep count and warn them when the server is close to limits, or impose your own smaller limit per visitor.
Note, there are regulatory requirements in place where you have to tell your visitor if you are tracking them.