OpenVPN runs over both TCP and UDP. Knowing when to pick each one can be the difference between a fast connection and a frustrating one.
UDP is fast and lightweight, which makes it the better default for streaming, gaming and general browsing. It does not wait to confirm delivery, so it keeps latency low.
When to switch to TCP
TCP checks that every packet arrives, which adds overhead but improves reliability on lossy or heavily filtered networks. Because it uses port 443 — the same as HTTPS — it also slips through restrictive firewalls that block UDP.
Rule of thumb: start on UDP for speed, and fall back to TCP if a network is unstable or blocking you. The SlickVPN client lets you flip between them in a click.
