Slow copies and throttling (429 / 503)

SharePoint Online limits how fast one account can work. The app slows down and retries automatically.

What happens

When SharePoint Online is busy, it answers 429 Too many requests or 503 Server too busy. SharePoint Migrator waits as long as SharePoint asks and retries automatically. Nothing is lost, but the copy takes longer.

Make large migrations faster

• Run big copies outside business hours, or schedule them with Schedule.
• Limit Version history to the latest versions you need.
• Split very large sites into several copies, for example one per library.
• Use Copy if newer (incremental) for later runs, so unchanged items are skipped.

Updated 2026-10-17