Error messages

“A server with the specified hostname could not be found.” on Mac

This is the macOS text for error -1003. The Mac could not turn the server's name into an address. DNS failed, or the name does not exist.

Applies to: All current macOS versions. The text was checked on macOS 27.2.Checked: 29 October 2026

Symptoms

  • An app shows “A server with the specified hostname could not be found.”
  • The app may show NSURLErrorDomain and -1003.
  • Safari shows “Safari Can’t Find the Server” for the same name.

Likely causes

  • No internet connection. Without a connection, no name resolves.
  • A DNS problem. The DNS server does not answer, or it has no answer for the name.
  • A VPN with its own DNS. Names inside a company network resolve only through the company's DNS. See Internal names do not resolve on a VPN.
  • A name that does not exist. A typing error, or a server that was removed.
  • A DNS filter. Some DNS services and filters answer that blocked names do not exist.

How to check

  1. Look up the name through the macOS resolver. No address lines means that the lookup failed.

    dscacheutil -q host -a name example.com

  2. Ask a public DNS server directly. An answer here, but not above, points to your DNS settings.

    dig +short example.com @1.1.1.1

  3. Show the DNS servers that the Mac uses now.

    scutil --dns

  4. Ping an address on the internet. This test does not use DNS.

    ping -c 5 1.1.1.1

How to fix it

  1. If ping works but lookups fail, fix DNS. See DNS not resolving on a Mac.

  2. Flush the DNS cache, then try again. See Flush the DNS cache on a Mac.

  3. For a company name, connect the VPN first.

  4. If a DNS filter blocks the name, allow it in the filter.

With Kilobat

  1. Kilobat's connection doctor tests the name layer by layer: network, proxy, DNS, rules, IPv4, IPv6, TLS and the server. It names the layer that failed.

    kilobat why example.com

  2. Read the DNS servers, or set a public DNS service for a test. Changes need an administrator password.

    kilobat dns

  3. These Kilobat checks are free. AI agents run them through MCP with diagnose_connection and diagnose_network. See Find why one site or API won't connect.

Questions

What is NSURLErrorDomain -1003?

It is the cannotFindHost error of Apple's URL Loading System. Apple describes it as a host name that could not be resolved.

Sources

Sources checked on 29 October 2026. Man pages are the ones installed with macOS; open one with man <name> in Terminal.