Quickly Compare Two Windows Folders And Their Contents


WinMergeLast week I wrote about a problem I was having with my PC backup regime. Some files were not being backed up, and it turned out that there was a problem with their dates. I found a great freeware tool to tweak their dates, and you can read about my experience at http://www.techsupportalert.com/content/best-tool-tweaking-files-dates-a... if you're interested.

I'm based in the UK, where today is a public holiday. So I took the time to do some more general maintenance on my computer, including my backups. And the first thing I did was to compare the size of the most important folder on my PC with the size of the folder on my backup drive. Needless to say, I was expecting them to be identical. But they weren't. There are around 32,000 files in total, and a couple of hundred of them were missing.

An investigation was clearly called for. And because my backup drive is just that, ie a standard drive, it was easy. After a little searching for a program to do the job, I settled on WinMerge. It's a 6 MB download from http://winmerge.org/?lang=en and runs just fine on Windows 10. It's reputable according to Web of Trust, and malware-free according to VirusTotal.

WinMerge can do lots of things (so be careful which options you choose!). When you start it up, and supply it with the names and locations of 2 folders, it performs the job that I wanted. Namely, to compare the contents of those 2 folders (and all their subfolders, if you want), to tell you whether the contents are identical or not. By default, the program checks every byte of every file. I changed this to check only the name, date and size, which speeded up the process and was sufficient for my needs.

In just a couple of minutes I had the answer to my query. The folder I'm backing up is actually my Dropbox folder, which seems to contain a number of hidden cache folders that Dropbox uses for its own purposes. These weren't getting backed up, which accounts for the discrepancy.

I can stop worrying now. And WinMerge is definitely staying on my PC because it's a very useful tool.

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Thanks for this suggestion
I havent found a freeware program that is able to compare folders with a lot of data quickly
I tried WinMerge with my current hard drive (1.5TB drive), it just cannot compare the original drive and the backup drive in a reasonable time frame

I therefore still rely on commercial software to do this valuable task
I will be delighted when I find freeware that can compare large data folders in less than 2 minutes, the way some shareware programs can

I've used FreeFileSync (FFS) for years because it is open source and keeps the correct folder and file timestamps - normally compare on file time and size for that reason. Other programs have worked for me but FFS is my preference.

I ran a quick test to confirm that the create and modify dates were correct on a synchronised folder using the latest version of FFS.

There's a Comparison of file synchronization software at Wikipedia.



Remah, the comparison data is brilliant. I learned of features I wouldn't have imagined. Than you for the resource, and the education!

A comment on both your requirements--efficient backup and folder comparison.

I was using Microsoft SyncToy for years to perform my backups, and thought it was really good. Then I moved to FreeFileSync a couple of years ago because I found it was significantly faster and also presented more flexible ways of filtering the sync operations. One of those filters will very quickly give you the files that are missing in the other folder. You can just run the Compare mode without actually performing the Sync action.

I've been using it for years and it has saved my bacon on many occasions when setting up back-up and recovery for client companies.