Mac Migration Assistant Errors — Transfer Failed & Stuck Progress

Fix macOS Migration Assistant errors including stuck transfers, 'could not be copied' errors, network transfer failures, and Time Machine migration issues. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: Migration Assistant transfers data between Macs via direct cable, Wi-Fi, or Time Machine backup. Transfer can take hours for large data sets — appearing stuck at a percentage for extended periods is normal. Wi-Fi transfers are much slower than Thunderbolt cable transfers. Some applications with copy protection may not transfer successfully. User account conflicts can prevent migration if the same username exists on both Macs. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: Network instability during Wi-Fi transfer causing disconnections. Insufficient disk space on the destination Mac. Corrupted files on the source Mac causing copy failures. User account name conflict between source and destination. Antivirus or firewall on either Mac blocking the transfer protocol. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Use Thunderbolt cable instead of Wi-Fi for reliable, fast transfer. Ensure destination Mac has more free space than source Mac's used space. On source Mac: run Disk Utility First Aid to fix any file system errors before migration. Disable firewall on both Macs during transfer: System Settings > Network > Firewall > Off. If transfer fails repeatedly, use Time Machine backup migration: create backup on external drive, then migrate from it. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Mac Error Codes collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.