If you’re synchronizing directories or backing up data, it’s a good idea to double-check that the copy you’ve made is actually identical to the original. It is possible for issues to occur where data doesn’t copy across perfectly, or some data doesn’t copy across at all.
If this sort of copy failure happens to an important document, and you don’t notice, you could end up with data loss. WinMerge is a tool that allows you to compare the contents of two directories. You can see if there are any missing files or if any of the backed-up files are different from the originals. This guide will walk you through installing and using WinMerge to compare the files in two folders.
You can install WinMerge for free from their website here. Just click the green “Download Now!” button in the top right corner to download it from SourceForge. Once the installer is downloaded, double-click it to start the installation wizard.
The first page of the installer is the licence agreement, click “Next” to agree and continue. The second page allows you to configure which features to install. By default, all extensions are enabled and there’s no real reason to turn them off – leave these options as they are. If you want to install an extra language pack, you can select one or more of the many options in the language list at the bottom.
Once you’ve selected the features you want, click “Next” to continue. The next page covers additional tasks. Here, there are checkboxes to enable File Explorer context menu integration, which allows you to launch WinMerge from the right-click menu File Explorer. Other options include creating a desktop shortcut and adding WinMerge to your system path, which you can leave disabled. Once you’ve selected which features you want to enable, click “Next” to continue.
The final page just shows what options you’ve selected, so double-check them, then hit “Install” to begin the installation process. Once the installation has completed, you’ll see a short message from the developers, click “Next” to skip it, then click “Finish” to close the installer and launch WinMerge.
Once WinMerge is open, press the Control+O hotkey combo to open a new comparison. To select a folder, click “Browse…” on the far right just under the “1st File or Folder” bar. Use the browse feature to select a folder that you want to compare.
Within the browse window, you need to enter the folder you want to compare, then click “Open”. If you only select but don’t enter the folder you want to compare, the browse window will enter the folder for you. When you’ve selected the first folder, repeat the process for the second folder below it. Once you’ve selected both folders that you want to compare, ensure that both “Read-only” checkboxes are ticked. You also need to make sure that the “Folder Filter” is set to the default “*.*”, to compare all files. Once you’ve completed setting up the comparison, click “Compare”.
With large folders containing a lot of files and subdirectories, the comparison process may take a while to complete. Once it has completed, you’ll see a list of all the files in the folders. By default, the results table lists: the filename, the path of a subdirectory, the result of the comparison, the edit dates of the file in both folders and the file extension for each file in the compared folders.
Tip: You can change which columns appear by right-clicking a column header and clicking “Customize Columns…”
The possible comparison results show if files or folders are identical or different. If the comparison says a file is “Right only” it means the file or folder was only in the second folder being compared and not the first. Conversely, “Left only” means the file or folder was only in the first folder being compared.
Different results are colour-coded to make spotting them easier. A white background means the files are identical, a yellow background means the files are different and a grey background means the files are only in one of the two folders being compared.
If you double-click on a folder, it will expand to reveal its contents. If you double-click on a file it will open a side by side comparison and will highlight the differences, if any, between the two files.
If you have a large number of files it may be convenient to hide all of the files that are identical, to make it easier to identify differences. To do so, click “View” in the top bar, and then untick “Show identical items” by clicking on it.
Each comparison you run opens in a new tab. To start a new comparison, click on the “Select Files or Folders” tab in the far left, change the targets and click “Compare” again. If you only want to update the existing comparison, you can click the refresh icon on the far right or press the F5 key.
Patrick Burwell says
We need a tool that will compare and copy unique data between folders and ONLY overwrite from Source to destination if the source is newer. Apparently robocopy will DELETE unique files in the destination using the ‘/MIR’ command. Mirroring should do just that, mirror the contents between the TWO, not delete unique files; Will WinMerge solve this issue?
Anahid Avakian says
I found this very helpful, but like Javier Reinoso, I wish I could save the results. I had no problem with external files, and if you attach your phone to a laptop via cable you can easily compare phone & computer.
Javier Reinoso says
A pity that WinMerge does not save the results, it only saves the directories to compare, not all the results…
And if the directories to be compared are very large – I have 2 directories with almost 350,000 files each – it sucks that I do the comparison again…
Except for that, WinMerge seems to me the best, it compares excellent, it shows where the differences are, it’s very good, it’s a shame that it has a bug, it would be very easy to do, it would save the different files and I wouldn’t have to recalculate. .
Works very well, even if it takes time with large drives …. ;)
External drives, no problems.
I can see a number of problems if you tries to compare files on a “phone”. :)
Sid Lo says
I did everything according to the instructions. After I hit compare I got the results table, just like the instruction says. All the folders are white except some that are grey. Here’s the problem: When I double click on a grey folder nothing happened. It didn’t review its contents. The results screen remained unchanged.. Please advise.
same prob as others. won’t let you compare from external drives !! only on your computer’s hard drive – pretty useless in the days on 5+ tb drives.
is there nowhere in the software to allow it to include external drive???
Dean Mathias says
Extremely helpful, i needed to compare a Network drive with and external SSD before moving the contents to a SharePoint site, the network drive was several hundred Gb in size and the software showed up several issues between both drives. Which were easily resolved.
without going into detail I’ll just say that this is what I needed, It will help a great deal to sort out thousands of music files over 3 hard drives which are backups but not all are exact so finding what is missing on each one to make them completely the same. Good job to the people that that developed the software and thankyou for making it free.
I’ve the same issue as Matt does.
need to comp[are two directories on phone and pc.
Not particularly useful for my purpose; wouldn’t recognize directories on my phone as valid comparison folders
Thanks for this quick and concise tutorial…just what I was looking for!
Not particularly useful for my purpose; wouldn’t recognize directories on my phone as valid comparison folders. Had two almost identical folders containing my music library (one on my phone, one on my PC. My music library on my PC is a whole drive partition, while the library on my phone is a folder on the internal storage. No matter what I tried, when I went to open the directory on my phone, it griped that it could not open the file or location because it could not be found or was an invalid location. Was trying to find out what the difference was between the two was; The library on my PC takes up 115 folders, whereas the library on my phone takes up 114 folders, and I couldn’t figure out what folder was the odd one out. Ended up having to just re-copy the entire 76GB again because it doesn’t work.
This .. is … good! I wanted to compare two folders (original and old backup folders). As anticipating, it found the files where I said “Yep, I remember doing that now”.
It might be too manual for many, but this manual simplicity brings fast and simple comparisons (if configured so) that bring peace of mind !
Very helpful, Thanks!
Very helpful, clear and concise. Thank you !
Julie McLaughlin says
how do I delete one of the two that are identical?
george comm says
Have you ever looked at another open source app called FreeFileSync? If so how do they compare?
Extremely helpful – well written, clear and easy to follow.
Frans Van der Walt says
Can the function include Sub-sub folders?
After the comparison, is there then an option to move the latest file / folder ??
Robert R Richard says