|Linux / BSD|
PeaZip can be used as duplicate files finder, searching binary identical files in order to de-duplicate data for saving disk space occupation, or improving compression through elimination of redundancy of input information, using various detection methods:
Identify duplicate files
When browsing a filesystem (not inside a compressed archive) the file browser can show file checksum / hash value on demand in last column, allowing to identify binary identical files which have same checksum/hash value.
Clicking the name of the function (in context menu, "File tools" group) will display hash or checksum value for all (or selected) files.
Clicking "Find duplicates" will display size and hash or checksum value only for duplicate files - same binary identical content featured in two or more distinct files - and report the number of non-unique files identified.
In both cases, sorting for CRC column allows to group all files (in same folder, or same search filter) with identical hash or checksum.
The verification function can be set in main application's menu: Organize, Browser, Checksum/hash), a wide selection of algorithms can be selected, ranging from simple checksum functions as Adler32, CRC family (CRC16/24/32, and CRC64) to hash functions like eDonkey/eMule, MD4, MD5, and cryptographically strong hash as Ripemd160, SHA-1 and SHA-2 (SHA224/256/384, and SHA512), and Whirlpool512.
When browsing an archive this on demand verification is not available, but (if supported by the archive format) the CRC column will display data integrity information, i.e. CRC32 in ZIP archives, allowing to sort archive content by CRC column to group identical files and find out duplicates.
Find similar images
When browsing a filesystem, PeaZip can display thumbnails of graphic files: context menu, organize, check show picture thumbnails, or select a file browser's preset style showing thumbnails.
While checksum/hash based inspection allows to find exactly identical files (and images), thumbnails allows the user to find similar images (i.e. same picture or graphic saved in different formats, or with different color depth or compression settings, or scaled to different sizes), to help in deciding if the (pseudo)duplication is acceptable, and what copy to keep.
Verify multiple checksum and hash values at once
Check files utility in "File tools" submenu (context menu) allows to compare multiple hash and checksum algorithms of multiple files at once. Employing multiple functions, and relying on cryptographically strong hash algorithms as Ripemd, SHA-2, Whirlpool, can identify even malicious attempt of forging identical-looking files.
Alternative method: byte-to-byte comparison
Compare files utility in "File tools" submenu performs byte to byte comparison between two files; unlike checksum/hash method it is not subject of collisions under any circumstance, and can report what the different bytes are - so it not only tells if two files are not identical, but also what changes were made between the two versions.
Topics: how to find duplicate files on Microsoft Windows and
Linux systems, compare and deduplicate content,
detect redundant data, remove identical files wiki, calculate checksum
algorithm, compute hash
FIPS, identify similar images, seemingly identical files.
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