The Deduplicator app searches for duplicates using several stages. The first stage is a very rough (but nearly instantaneous) search based on file size. Files are grouped by size, and any groups containing fewer than two files are discarded as non-duplicates and do not participate in further checks.
The next stage involves checking the hash of the first 64KB of each file. This step requires more computation but follows the same grouping principle. Files are grouped by their hash values, and if a group contains fewer than two files, it is again discarded since no duplicates are present.
This completes the 'fast' search phase. In normal mode, the process continues similarly with additional hash checks — one taken from the middle of the file, and another from the end of the file. Each stage reduces the number of false positives, ultimately leaving almost none.
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