How does the duplicate file scanner work in RJL System Cleaner?

The scanner uses a fast two-pass approach to find duplicates efficiently:

Pass 1 -- Size grouping: Files are grouped by file size. If a file has a unique size (no other file is the same number of bytes), it cannot be a duplicate and is immediately skipped. This eliminates most files very quickly without reading their contents.

Pass 2 -- Hash verification: For files that share the same size, the scanner reads a small portion of each file (the first 64 KB) and generates a hash fingerprint. Only if these partial hashes match does it compute a full file hash to confirm the files are truly identical byte-for-byte.

This two-pass approach means the scanner only reads the full contents of files that are very likely to be duplicates. It can check thousands of files in seconds without significant slowdown to the overall scan.

Duplicate groups are displayed in the results: each group shows the file hash, file size, number of copies, and every file path with its last-modified date. The oldest file is marked as the "original" and the rest are marked as "duplicates."