WinMerge: How to Merge Duplicate Files and Folders

Finding Duplicate Files and Folders on Windows with WinMerge

While browsing through the MakeUseOf Answers archive, a frequently asked question surfaced: how can duplicate files or folders be merged on a Windows PC? Linux users benefit from straightforward tools for file comparison, such as the 'diff' command.

MakeUseOf has previously highlighted various file merging applications, including guides on merging PDF files and video files. However, a need often arises for simply merging documents or folders containing lists of seemingly identical files.

The process isn't as streamlined in Windows as it is in Linux, but the situation is not uncommon. Perhaps two directories have been used for a long time, and despite synchronization attempts, they no longer perfectly align. Alternatively, multiple copies of a document may exist, leaving uncertainty about the most recent version, with a desire to avoid data loss.

WinMerge, a free and open-source application, provides "diff" functionality for Windows users. It accepts three inputs: the file or folder to display on the left, the file or folder to display on the right, and an optional filter for advanced users to refine the comparison and merging process.

Comparing Two Folders for Duplication

A common use case for this application is comparing two folders presumed to be synchronized, but where doubts have arisen about their true duplication. WinMerge can not only confirm whether the folders are duplicates, but also pinpoint the exact differences, enabling informed decisions about achieving true duplication.

To demonstrate this functionality, two test folders were created with identical text and image files, differing only by the inclusion of an extra text file and an extra image file in the second folder. Selecting these folders for comparison initiated the process, with results appearing within seconds.

WinMerge immediately identified the discrepancies: MyImage5.bmp and TextDocument4.txt were found exclusively in Folder 2. The application also displays file modification dates, revealing potential differences in update times. This is useful when files share a name but have varying modification dates.

Comparing Two Files for Duplication

To test file comparison, TextDocument1.txt and TextDocument2.txt in Folder2 were modified to contain identical text – the first three pages of Moby Dick. Then, three unique sentences were added to the first file, and one unique sentence to the second. The goal was to determine if WinMerge could accurately isolate and identify all differences.

Document1 was set on the left and Document2 on the right, with no filters applied for a line-by-line, word-by-word comparison.

The application successfully identified every alteration. The lines containing changes were highlighted, with the alterations themselves further emphasized for quick review. Importantly, the interface allows direct editing of either document within the comparison view, similar to a standard text editor.

A unique line from Document1 was highlighted and pasted into the corresponding line in Document2. This process can be applied to individual lines or entire paragraphs, allowing flexible editing within the comparison window.

Performing a Merge Operation

While manual copying of differences is possible, WinMerge offers automated merging capabilities. The "Merge" menu provides options for streamlining the process.

The first nine options are "semi-automatic," allowing users to step through each difference and copy content to either the left or right document. The final two options provide fully automated merging.

After reviewing the differences and confirming the desired content, selecting the target file and choosing "Copy All to Right" or "Copy All to Left" automatically merges the unique content, resulting in identical files or folders.

Have you encountered the need to compare or merge duplicate files or folders? Have you utilized the WinMerge duplicate files utility? Share your experiences and insights in the comments below.