---
title: "A server with the specified hostname could not be found (-1003) · Kilobat Guides"
url: "https://kilobat.app/guides/server-hostname-not-found.html"
description: "An app on your Mac says A server with the specified hostname could not be found. Check the name, DNS, VPN and proxy, and fix the failing lookup."
---

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](https://kilobat.app/guides/vpn-split-dns-internal-names.html).
- **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](https://kilobat.app/guides/dns-server-not-found.html).
2. Flush the DNS cache, then try again. See [Flush the DNS cache on a Mac](https://kilobat.app/guides/flush-dns-cache-mac.html).
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](https://kilobat.app/guides/recipes/why-cant-it-connect.html).

## 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

- Error text in CFNetwork.framework, macOS 27.2 (Localizable.loctable)
- [Apple Developer: URLError.Code cannotFindHost (-1003)](https://developer.apple.com/documentation/foundation/urlerror/code/cannotfindhost)
- [Apple Support: Change DNS settings on Mac](https://support.apple.com/guide/mac-help/change-dns-settings-on-mac-mh14127/mac)
- dscacheutil(1), dig(1) and scutil(8), man page installed with macOS 27.2

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

## Related guides

- [DNS not resolving on a Mac](https://kilobat.app/guides/dns-server-not-found.html): When DNS fails, the Mac cannot change a name such as apple.com into an IP address.
- [Safari can’t find the server on a Mac](https://kilobat.app/guides/safari-cant-find-server.html): “Safari can’t find the server” usually means that the Mac could not get an address for the site name.
- [Flush the DNS cache on a Mac](https://kilobat.app/guides/flush-dns-cache-mac.html): macOS keeps DNS answers for some time.
- [Internal names do not resolve on a VPN](https://kilobat.app/guides/vpn-split-dns-internal-names.html): macOS can send queries for one domain to one DNS server and other queries to another.
- [ERR_NAME_NOT_RESOLVED in Chrome on Mac](https://kilobat.app/guides/err-name-not-resolved.html): Chromium describes this error as: “The host name could not be resolved.” Chrome could not get an address for the site's name.