File SHA-1 Checksum
Calculate the SHA-1 checksum of a file.
A SHA-1 fingerprint
SHA-1 is a hashing algorithm that produces a checksum — a fingerprint of a file's contents used to verify integrity. This calculates a file's SHA-1 checksum in your browser, so the file never leaves your device.
Load a file to calculate its SHA-1 checksum.
Where SHA-1 still fits, and where it doesn't
SHA-1 remains widely used for integrity checking — confirming a file downloaded completely and was not accidentally corrupted, where you compare the computed checksum against a published one. For that everyday purpose it works fine, and many systems and tools still publish SHA-1 checksums. However, there is an important caveat: SHA-1 is no longer considered secure against deliberate tampering, because it has been shown to be possible to craft two different files with the same SHA-1 checksum, which defeats its use as a security guarantee. So for verifying a file has not been maliciously altered, a stronger algorithm like SHA-256 is the right choice, while SHA-1 is reasonable for detecting accidental corruption. Computing it locally in your browser means you can checksum sensitive files without uploading them, keeping the verification entirely private on your own device.
Questions & answers
Is SHA-1 still safe to use?
For detecting accidental corruption, yes — but it is no longer secure against deliberate tampering, since crafted collisions are possible, so use SHA-256 for security.
What is a SHA-1 checksum for?
Verifying a file downloaded completely and unaltered, by comparing the computed checksum against a published one.
Is my file uploaded?
No. The checksum is computed in your browser, so the file never leaves your device.