File Integrity Checker

File integrity checking confirms that a file is exactly what it should be — byte for byte — and hasn't been corrupted, tampered with, or swapped since you last trusted it. This tool does three jobs in one place. Verify a file compares a download or received file against a checksum the publisher gave you, so you know it arrived intact. Generate checksums produces SHA-256 (and other SHA) hashes for any file you select, ready to share or archive. Compare snapshots hashes every file in a folder and diffs it against an earlier snapshot, flagging anything added, removed, or modified.

Everything runs locally through the Web Crypto and File APIs. Your files are read directly in the browser and never uploaded, so even large or sensitive files stay on your device. Use it to validate software downloads, catch silent bit-rot in backups, or watch a directory of important documents for unexpected change.

Confirm a file matches an expected checksum (e.g. one published on a download page). The file is hashed entirely in your browser and never uploaded.

Frequently asked questions

What is a checksum and why does it matter?
A checksum is a hash (such as SHA-256) that acts as a fingerprint for a file. If even one byte changes, the checksum changes completely, so comparing checksums tells you whether a file is identical to the original.
Are my files uploaded anywhere?
No. Files are read and hashed entirely in your browser with the Web Crypto API. Nothing is sent to a server, so private and large files never leave your device.
Which hash algorithms are supported?
SHA-256 is the default, with SHA-1, SHA-384, and SHA-512 also available. SHA-256 is recommended for verifying downloads and detecting tampering.
How do snapshots detect changes?
The tool records a hash for every file in the folder you select. Re-running it later and comparing the two snapshots reveals which files were added, removed, or modified.
Can I verify very large files?
Yes. Because hashing happens locally, you can check large ISOs, archives, and backups without any upload size limit.