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File Content

This file property can be used to find files with the same or similar content.

Comparison Method

The following methods are available for the content comparison:

• Byte by byte
• Checksum MD5 (128-Bit)
• Checksum SHA-1 (160-Bit)
• Checksum SHA-2 (256-Bit)
• Checksum SHA-2 (384-Bit)
• Checksum SHA-2 (512-Bit)

Byte by byte

With this comparison method, the content of the files to be compared is read in chunk by chunk and compared with one another. With a specified percentage match of 100%, the file comparison stops as soon as a difference is found. If the percentage match is less than 100%, the complete file content is always compared so that the percentage match can be calculated.
Example: If a percentage match of 90% is specified, all files that have a match of 90% or higher are classified as duplicates.

Checksum

The checksum method reads the complete file content and creates a checksum of the content for further comparisons. Using a checksum could be much faster than a byte-by-byte comparison when you compare a lot of files. Comparing only the stored checksum will avoid reading the complete content of these files again and again. See Speed Comparison Test.

Ignore ID3 Tags of MP3 files

This option enables you to ignore the following tags inside MP3 files:

• ID3v1
• ID3v2
• Lyrics3 v2
• APE v2

Info: AllDup also ignores ID3v2 tags at the beginning of the MP3 file that exists twice and ID3v1 tags at the end of the file that exists twice.

Ignore metadata of JPEG/CR2 files

With this option, only the compressed image data inside files with the extension "JPEG", "JPG" and "CR2" will be compared.

Ignore metadata of FLAC files

This option enables you to ignore all the metadata inside FLAC files.

First compare a data block at the end of the files

With this option a data block at the end of both files will be compared first. The file comparison will be stopped if the data blocks are not identical. Otherwise, AllDup continues the file comparison at the start of the file.

Block size of the read buffer

This option enables you to change the block size of the read buffer for the content compare.

1. The file comparison starts with a block size specified by the start value.
2. AllDup reads the block size from the two files into the memory and compares them.
3. The file comparison will be stopped if the data blocks are not identical.
4. Otherwise, the block size will be increased by the increment value until it reaches the maximum value and continues comparing the files (2).