Incremental copy is a migration option in your Operation mode settings that will replace an item at the destination only if the date modified field is older than that at the source, and copy new items from the source that don't exist at the destination. This aims to ensure that you are not overwriting newer files at the destination.

This article will take you through the default behavior of Incremental copy, so you can decide if it is the right option for your oncoming migration project.

With Copy if newer (incremental), ShareGate Migrate analyzes your source and destination list or library to determine which items or documents should be copied or updated.

ShareGate Migrate considers a file a match when it has the same file name in the source and destination library. It considers a list item a match when it has the same title and created date in the source and destination list.

If no match is found, the item is copied as a new item at the destination.

If a match is found, ShareGate Migrate looks at the last modified date to determine if the item should be updated or ignored at the destination.

Notes:

If your destination library does not have the same folder hierarchy as your source, ShareGate Migrate will not be able to find documents that are in different folders at the destination. This can result in some files and folders being duplicated at the destination.

Incremental Copy is not designed for large lists or document libraries. In this mode, ShareGate Migrate crawls the source and destination to read your content in batches of 1000 items simultaneously to determine what needs to be copied. So if you have more than a couple of thousand items, ShareGate Migrate will need to make many calls to obtain the data. This can result in your migration job going slowly or not starting altogether due to performance issues or throttling (on Microsoft 365).

If you are migrating an extensive list or document library, we recommend using Copy and replace, setting your Filter options to enable Time range filter, and setting the time frame to limit your migration to elements created or modified in your chosen range.

If versioning is enabled, ShareGate Migrate will add the new versions from the source at the destination. If the versioning is disabled, the destination item will be replaced.

Incremental Copy is not meant as a full synchronization option and will not identify or delete items at the destination that were deleted at the source. This avoids any potential data loss during the migration process. You will need to manually delete those items once your migration is complete.

When you use Incremental copy in a Copy structure and content site migration, ShareGate Migrate will only consider List Items and Documents. Any structural elements are updated based on the source since SharePoint doesn't keep a record of the modifications of your structural elements, such as site settings, columns, list settings, etc.

Incremental Copy does not check for permission changes from the source to the destination. It only validates the last modified date when copying.