Step 1

Step 1: Adjusting comparison settings

Before being able to start a scan, a few settings have to be configured. The first thing we will take a look at are the comparison settings.

The comparison criteria control how DoubleKiller determines if two files are equal. You can specify any combination of the following four criteria on the Comparison Options page by clicking their checkboxes. The advanced... buttons open additional windows offering more detailed settings for each criterion which are summarized in the white text boxes.

file name
Compares the file names. In the advanced comparison options you can specify if the complete name or only a part of it should be compared and if the comparison is case sensitive.
date
Compares the dates at which the files have been modified the last time. You can limit the comparison to certain parts of the date, e.g. year and month, or specify an allowed difference in the advanced comparison options.
size
Compares the file size / length. An allowed difference can be set in the advanced comparison options.
content
Compares the content of the files which is often the most important criterion.The advanced comparison options allow to limit the comparison to certain parts of the files and specify the comparison methods (fingerprint and/or byte-per-byte comparison).

If more than one criterion is selected, the files have to pass all of the selected comparisons to be considered duplicates. The relatively slow process of a content comparison is always done at last, so in general you should try to take advantage of anything you know about the duplicates you are searching for by using this knowledge to reduce the amount of content comparisons needed, i.e. minimize the number of files by choosing the right folders and filters (discussed in the following steps) and select as many comparison criteria as possible in your case.

Comparison criteria examples

The best combination of criteria is always dependant on the task you want to perform. To help you, here are some hints on which combination to choose for which purpose:

If you know you have 1:1-copies of files or even complete folders spread on your computer, you should select name, size and date comparison. This will find files you have copied somewhere e.g. for backup purposes without renaming or modifying them in any way. You can also select a content comparison for additional safety, but this is mostly unnecessary.
If the above applies, but you may have renamed the files, just deselect name comparison to find identical files with different names. A content comparison is recommended in this case to make sure no false positives are detected which have the same size and date just by coincidence.
If you have different versions of the same files stored in different folders, but not renamed, you should select a file name comparison only. In this case it is strongly recommended to only scan the specific folders these files are located in (not your complete hard disk) and to manually check the scan results as there might be files coincidentally sharing the same name. You could also use a size comparison with a tolerance of e.g. 50 kB (this depends on the file type... text files will not differ that much in size as multimedia files) to eliminate most false positives. If your files follow a certain naming scheme, e.g. 'myfile[1].cad', 'myfile[2].dat', you can use the advanced filename comparison options to exclude e.g. your numbering from the comparison.
To just scan for any files having exactly the same content without regarding file names or dates, select size and content. This allows to find any intentional or unintentional duplicates, e.g. in your music archive, image collection or downloaded files folder. If you plan to scan your complete disk, it is strongly recommended that you manually check the results and do not touch any files in the Windows folder or other files you are unsure about!
To create a list of all files in the given directories, using the given filters, deactivate all comparison criteria. This way you can use DoubleKiller as a fast file searcher, which is especially useful when searching inside zip archives or catalog files - or when you want to create a catalog file.