Most free online virus scanners cap uploads at a few hundred megabytes, and Google Drive warns that big downloads are "too large for Google to scan for viruses". If you need to check a 4 GB ISO, a game folder or a long video, you need a different approach.
Why online scanners have size limits
Upload-based scanners must receive your entire file and then run it through their engines. Bandwidth and processing costs grow with size, so they set limits — VirusTotal's website, for example, accepts files up to 650 MB. Uploading several gigabytes over a home connection would also take a long time.
Option 1: Hash check in your browser (no size limit)
The iMalware scanner never uploads the file. Your browser reads it in 4 MB chunks, computes the MD5 hash locally and checks it against 1,045,564 known malware hashes. Because only the fingerprint is used, a 6 GB file works the same way as a 6 KB one; it simply takes longer to read from disk. On a typical modern computer expect roughly a few seconds per gigabyte, depending on the disk and browser.
As with any hash check, this detects known malware files, not brand-new variants.
Option 2: Scan locally with your antivirus
Installed antivirus software has no upload limit. On Windows, right-click the file or folder and choose Scan with Microsoft Defender. On Linux or macOS, ClamAV's clamscan works; note that ClamAV skips files above its configured maximum size by default, which you can raise with options such as --max-filesize and --max-scansize.
Option 3: Verify the checksum
Large downloads such as Linux ISOs, firmware and official game or software installers usually come with a published SHA-256 or MD5 checksum. Compute the hash of your copy (see the commands here) and compare. If it matches the value on the official site, you have the exact file the publisher released, untampered.
The Google Drive "too large to scan" warning
Google Drive only virus-scans files below a size threshold, so for larger files it shows a warning such as "file.mp4 is too large for Google to scan for viruses. Would you still like to download this file?" This doesn't mean the file is infected; it means Google didn't check it. If it is your own file, or a media file from someone you trust, the risk is low. If it's an executable or archive from a stranger, download it but don't open it, then check it with iMalware or your antivirus first.
Are big video, image or audio files dangerous?
Plain media files are data, not programs, so a large MP4 or MKV is rarely a threat in itself. The risk comes from disguised executables (movie.mp4.exe), files that make you "download a codec", and rare media-player vulnerabilities. Keep your player updated and see which file types can contain malware.
Frequently Asked Questions
Is there a virus scanner with no file size limit?
Yes. iMalware has no hard size limit because the file is hashed in your browser in chunks and never uploaded. Installed antivirus software such as Microsoft Defender also has no upload limit.
How long does it take to check a 5 GB file?
With iMalware the time is mostly spent reading the file from disk. On a modern computer with an SSD it usually takes well under a minute; slower disks and older devices take longer.
Why does Google Drive say a file is too large to scan for viruses?
Google Drive only scans files below a size threshold. Above it, Drive shows a warning and lets you download anyway. The warning means the file wasn't checked, not that it is infected.
Can a large file be checked online without uploading it?
Yes, with a hash lookup. Only the file's fingerprint is compared against a malware database, so file size doesn't matter.