What is API Port / API-SSL (MikroTik)?
The MikroTik API port is a service on RouterOS (port 8728, or 8729 for the SSL-encrypted version) that lets external software control the router programmatically. Through it, a billing panel or script can do anything Winbox can — create hotspot users, change a subscriber's speed, disable an account, read traffic counters — by sending structured commands instead of clicks.
This port is what connects an ISP's billing system to its network: when a customer's recharge succeeds, the panel calls the API and the router re-enables them within seconds, no technician involved. The SSL variant (8729) encrypts the channel so router credentials do not cross the network in readable form — essential when the panel is cloud-hosted. Standard hardening: use API-SSL only, and firewall the port to the panel's IP.