> For the complete documentation index, see [llms.txt](https://moverdocs.files.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://moverdocs.files.com/migration-behavior/file-matching-and-data-integrity.md).

# File Matching and Data Integrity

Mover compares source and destination paths without regard to case or accents. At a matching path, it uses the item type and reported file size to decide whether a transfer is needed.

A file transfers when it is missing from the destination or when the source and destination report different sizes. When a file with the same name and size already exists, Mover leaves it in place. Modified time and checksum are not used to decide whether the file needs to transfer.

This comparison depends on both systems reporting file sizes accurately. An incorrect size can cause Mover to skip changed content or repeatedly transfer a file that is already present. When the project requires content-level verification, validate the destination with a separate checksum or inventory process after the migration.

For Amazon S3, Azure Blob Storage, and Google Cloud Storage sources, Mover also detects when a file changes after the run starts. It skips the changing file rather than transferring a partial version. Rerun the migration after the source file is stable.

Rerunning a migration repeats the comparison. It transfers files that are missing or report a different size, but it does not recopy same-size files merely because their modified times or contents changed.

See [File and Folder Compatibility](/migration-behavior/file-and-folder-compatibility.md) for the way case-only duplicates and unsupported names affect path matching.