You have a file on your computer and you are not sure if it is safe. The fastest, free, and legal way to check it without creating an account or entering a card is to submit the file to VirusTotal or MetaDefender Cloud, then verify the file's checksum against the publisher's official hash using your operating system's built-in tools. These two steps together give you a reliable answer before you double-click anything.
What to Use and Who Each Suits
VirusTotal
VirusTotal scans a file or a checksum against many antivirus engines at once. You upload the file or paste a hash, and it returns results from dozens of scanners. The public service is free and does not require a credit card. The documentation mentions a user registration key, but the page does not state that a card is required for the free tier. It works for anyone who wants a second opinion from multiple engines without installing software. If you are on a slow connection or have a small file (under 650 MB for the web upload), this is your first stop.
MetaDefender Cloud
MetaDefender Cloud also accepts file uploads, URLs, IP addresses, and hashes for scanning and malware analysis. A free file-scan service is advertised on the page. The retrieved page does not document whether an account or card is required, so you can try it without signing up first. This suits users who want an alternative to VirusTotal or who need to scan a URL or IP address alongside the file.
Checksum Verification (Built-in OS Tools)
Checksum verification compares the SHA-256 or SHA-512 hash of your downloaded file against the official checksum published by the software creator. If the two hashes match exactly, the file has not been altered or corrupted. This is a local operating-system feature on Windows, macOS, and Linux, so it costs nothing, requires no account, and works in every country. It suits anyone who downloads software from a trusted source that provides a checksum on its download page. You do not need to upload your file anywhere, which is useful for large files or sensitive data.
The Thing Most Readers Get Wrong About Browser Warnings
A browser warning, "This file may be harmful" or "Windows protected your PC", is a signal to stop and inspect the file, not a verdict. The warning only tells you that the browser or the operating system detected something suspicious, such as an unknown publisher, a low download count, or a heuristic match. It does not prove the file is malware, and a clean scan alone does not prove it is trustworthy if the source or signature cannot be verified. Many legitimate open-source programs trigger warnings because they are not signed with a code-signing certificate that costs money. You must still check the hash and run a multi-engine scan before you decide to open it.
What to Check Before Committing to One Method
File Size and Upload Limits
VirusTotal's web upload has a file size limit. If your file is larger than that, you can compute the SHA-256 hash locally and paste the hash into VirusTotal's search bar instead of uploading the whole file. MetaDefender Cloud's free tier may also have a size limit; the retrieved page does not document the exact cap. For very large files, checksum verification is the only option that does not require uploading.
Privacy
Uploading a file to a multi-engine scanner sends a copy of that file to a third-party server. If the file contains personal data, proprietary code, or something you do not want shared, use checksum verification instead. The hash alone does not reveal the file's contents, and the scan is done entirely on your own machine.
Source Trust
A checksum match only proves the file you downloaded is identical to the file the publisher uploaded. It does not prove the publisher is trustworthy. If you downloaded from a mirror site or an unofficial link, verify the checksum against the hash published on the official website, not the mirror. For example, if you download LibreOffice, get the checksum from libreoffice.org, not from the site you downloaded from.
Multiple Engines vs. One
A single antivirus engine can miss a threat. VirusTotal and MetaDefender Cloud run many engines simultaneously, which increases the chance of detection. If only one engine flags a file, it may be a false positive. If ten engines flag it, you should delete the file. No single engine is perfect, and no multi-engine result is a guarantee of safety, but it is far better than relying on one scanner or a browser warning.
Frequently Asked Questions
Do I need to create an account to use VirusTotal?
The documentation mentions a user registration key, but the public web interface allows file uploads and hash lookups without an account. You can use it immediately without signing up or providing a card.
What if the publisher does not provide a checksum?
Then you cannot verify the file's integrity that way. In that case, submit the file to VirusTotal or MetaDefender Cloud and check the scan results. Also consider whether the source is reputable, a missing checksum on an official site is unusual for major open-source projects like Blender or VLC.
How do I compute a checksum on Windows without installing anything?
Open PowerShell, type Get-FileHash -Path "C:\path\to\your\file.exe" -Algorithm SHA256, and press Enter. The output is the SHA-256 hash. No account, card, or internet connection is required.
Can a checksum tell me if a file has a virus?
No. A checksum only confirms the file has not been modified since the hash was published. If the original file on the publisher's server was infected, the checksum will match the infected file. That is why you combine checksum verification with a multi-engine scan.
What does "Windows protected your PC" actually mean?
It means SmartScreen or Windows Defender detected an unknown or low-reputation file. It does not mean the file is definitely malware. You should still check the publisher signature, the hash, and the VirusTotal results before choosing to run it anyway.
Where this fits
This is one guide from Where to Download Software Safely.
