How to Verify File Integrity in Windows With FCIV
Follow the easy steps below to verify a file’s integrity with FCIV, a free checksum calculator:
Do the Checksums Match?
Now that you’ve generated a checksum value, you need to see if it equals the checksum value the download source provided for comparison. FCIV is a command-line tool but don’t let that scare you away. It’s very easy to use, especially if you follow the tutorial outlined below. For example, if the file is in Tim’s Downloads folder, the prompt in the Command Prompt window would read C:\Users\Tim\Downloads> after following this step from the Downloads folder. The easiest way to do this is to execute the dir command and then write down the full file name. Type the following in Command Prompt: That will generate a list of files in that folder. In this example, we want to create the checksum for a file called AA_v3.exe, so we’ll write that down exactly. Let’s say that the website we downloaded the file from decided to publish an SHA-1 hash to compare to. This means that we also want to create an SHA-1 checksum on our copy of the file. To do this, execute FCIV as follows: Be sure you type the entire file name—don’t forget the file extension! If you need to create an MD5 checksum, end the command with -md5 instead. The number/letter sequence before the file name in the Command Prompt window is your checksum. If they match, then great! You can now be completely certain that the file on your computer is an exact copy of the one being provided. It means that there were no errors during the download process and, as long as you’re using a checksum provided by the original author or a very trusted source, you can also be sure that the file hasn’t been altered for malicious purposes. If the checksums don’t match, download the file again. If you’re not downloading the file from the original source, do that instead. In no way should you install or use any file that didn’t perfectly match the checksum provided.
What Is a Checksum?
Fortunately, many websites offer a piece of data called a checksum that can be used to help verify that the file you end up with on your computer is exactly the same as the file they’re providing. A checksum, also called a hash or hash value, is produced by running a cryptographic hash function, usually MD5 or SHA-1, on a file. Comparing the checksum produced by running a hash function on your version of the file, with the one published by the download provider, can prove with near certainty that both files are identical.
