CrcCheckCopy - compare folders by the CRC hash of each file
CrcCheckCopy is a command-line utility that lets you compare the files of different folders. It generates a CRC32 for each file and stores it in one checksum file. This small file can then be used to either check/compare another folder hierarchy or be used as an integrity check of the same folder hierarchy. The files are compared in binary mode, meaning byte by byte. This way you can be sure that the files are exact, identical copies.
The checksum file enables you to compare folders on two remote computers without needing to transfer the whole folder structure over the internet. Other file/folder comparing utilities need concurrent access to both folder hierarchies and need to read (again) the files of the source directory (in most cases they contain some gigabytes spread in multiple files).
CrcCheckCopy is a console application (command-line tool) that runs on Windows and Apple MacOS.
You can use the comments section below for any other feature requests and suggestions related to disk/folder/file comparison tasks.
Who is it for?
- IT administrators, who must do reliable file copies of large volumes of data.
IT administrators can use CrcCheckCopy to ensure (with proof) reliable data copies to their managed servers in their data centers.
- Professionals in the DVD/CD authoring, mastering or mass-production industry
CrcCheckCopy was originally created for professionals in the multimedia sector. These included DVD/CD manufacturing factories, DVD/CD software authors, DVD/CD preprocessing, mastering studios.
CrcCheckCopy allows you to take a checksum file containing the CRC of each file on an incoming disk and when the processing of any files is completed, to verify the produced final disk. The utility can show which files have (expected) differences. This is something that cannot be done if you create a single CRC for the whole disk.
- Power users who want to ensure the reliability of their data copies.
Not all copies are 100% good. This might sound funny in the era where using the computer and making copies is so easy for anyone. But here are just a few examples of what can go wrong during a copy without the user noticing it:
- Some files do not get copied because of the limitation of the maximum directory length. The message shown by Windows will not explain to you which files were affected.
- USB flash disks worn-out while being used. Some of their files might become "corrupted" (this is not a moral term but a computer term meaning that the files were altered by defects of the medium).
- Copying to different files systems might alter the filename characters, e.g. Chinese or eastern European characters get converted to something that is compatible with the destination file system. These files might then become unreadable by other computers. You will most probably not see a warning about this during your file copy operation. It is a silent error.
- Accidental user mistakes, e.g. you accidentally drag and drop some files in a different folder (the accidental file move operation can every easily go unnoticed).
CrcCheckCopy can generate signatures (CRC32 checksums) of all the source files, and compare them with the destination copy, alerting you for any differences found.
You can even store the CheckCopy utility and the checksum file to the destination disk or folder so that the recipient of the copy can verify them at any time.
- People who want to archive data files and be sure that nothing has altered them, like in the case of long-time preservation.
- Storing the checksum stamps file (and the CrcCheckCopy utility itself) together with the archived files will give you the ability to verify the integrity of your data at any time in the future. Just run the utility in verification mode, using the existing checksum stamps file.
How are you using our file comparison and crc verification utility? Use the comments below to send us your use cases. You can help us fine-tune the software and/or add new uses for it.
How to compare the files between a source and a destination folder/disk/CD/DVD/NAS shared folder/Network share
To scan all files in a folder, e.g. "c:\my-source-folder", type
CrcCheckCopy /scan c:\my-source-folder
./CrcCheckCopy /scan /my-source-folder
The utility will read all files and store their CRCs in a file named "CRCstamps.txt", in the current directory.
You can open this file to observe its contents. The report will also contain a list of files that have zero size and a list of duplicate files.
To verify and compare another folder, e.g. "c:\my-destination-folder", type
CheckCopy /verify c:\my-destination-folder
./CheckCopy /verify /my-destination-folder
The utility will open the file "CRCstamps.txt" from the current directory, and verify that the files inside "c:\my-destination-folder" have the same CRCs.
A new text file "CrcCheckCopy-verification-report.txt" will be created in the current directory, listing any errors found.
For a more detailed description of how to compare the files of two folders see "How it works".