macOS Update Error 403 — Software Update Failed Fix

What Does This Error Mean?

macOS Update Error 403 means your Mac was denied access to Apple's update servers. It often appears as 'An error occurred while preparing the installation' or a simple 403 message in the update log. This is usually caused by network restrictions, a VPN blocking Apple, or a corrupted software update download on your Mac.

Affected Models

MacBook Air
MacBook Pro
iMac
Mac Mini
Mac Studio

Common Causes

A VPN or proxy server is blocking your Mac from reaching Apple's update servers
The partially downloaded update file is corrupted and needs to be cleared
Your Mac's date and time are incorrect, causing the connection to be rejected
A firewall on your router or network is blocking Apple's update servers
Your Apple ID session has expired and needs to be refreshed

How to Fix It

Turn off your VPN. If you use a VPN, disable it completely. Then go to System Settings > General > Software Update and try again.

VPNs route your traffic through different servers, which can trigger Apple's servers to reject the connection.
Clear the cached update download. Open Terminal (Applications > Utilities > Terminal) and type: sudo rm -rf /Library/Updates/* then press Enter. Enter your password when prompted, then try updating again.

This deletes any partially downloaded update files. macOS will re-download the update fresh on the next attempt.
Check your date and time settings. Go to System Settings > General > Date and Time. Make sure 'Set time and time zone automatically' is turned on.

An incorrect date causes Apple's servers to reject the connection due to certificate validation errors.
Download and install the update manually. Go to support.apple.com/downloads and search for your macOS version. Download the full installer and run it directly.

A manual install bypasses the Software Update system entirely, which avoids the 403 error.
Restart your Mac and router. A fresh network connection sometimes resolves the 403 error. Restart both your Mac and your router, then try Software Update again.

Restarting your router clears its temporary memory and can fix cases where the network itself is causing the block.

When to Call a Professional

This error is almost always fixable at home. If none of these steps work, Apple Support can walk you through a manual update using a downloaded installer from Apple's website. You can reach Apple Support at support.apple.com.

Frequently Asked Questions

Will waiting fix the error on its own?

Sometimes yes — if Apple's servers are temporarily overloaded (common after a new macOS release), waiting a few hours and trying again can fix it. But if the error is caused by your VPN or a corrupted download, waiting will not help.

Is it safe to delete the cached update files?

Yes — deleting the contents of /Library/Updates only removes partially downloaded update files. Your personal files, apps, and macOS itself are not affected. macOS will re-download the update files fresh on the next attempt.

Can I stay on my current macOS version if I keep getting this error?

Yes — you can keep using your Mac without updating. However, Apple releases security updates through Software Update, so staying behind on updates means your Mac may be exposed to security vulnerabilities. At minimum, install the latest security patches.