isResolvable()

True if the host name resolves in DNS. Performs a blocking DNS lookup.

isResolvable(host)  →  boolean

Every call is a DNS query on the proxy-resolution path. Using it as “am I on the internal network?” check makes every request wait for DNS and fails badly when DNS is slow or split.

Example

// prefer explicit domain lists; if you must, guard it:
if (isPlainHostName(host) && isResolvable(host)) {
  return "DIRECT";
}

Engine notes

Availability

Related rules

• DNS lookup on every request PAC-P001