The Duplicate Finder uses SHA1 checksum for file compare, only files with the same checksum are duplicates. This means:
- the app will not detect two files as duplicates, when they do not have the same bits,
- files with different names but same content are always detected as duplicates,
- if you've resized an image, even if the "content" is duplicate, the app will not detect it as it is not the same file anymore.
“SHA-1 is essentially a secure checksum for a data file. The SHA-1 checksum is based on a cryptographic standard. For a given file, SHA-1 produces a 160 bit encrypted output known as a “message digest.” It is highly improbable that a modified data set would produce the same message digest. If a file is changed during transit, its message digest also changes.” – read more