What is a file hash?A short fingerprint of a file’s exact contents; it shows sameness, not time or author

How a hash works

A hash function reads every byte of a file and produces a short string of letters and numbers. SHA-256, the one TimeBinder uses, always gives 64 hexadecimal characters, whether the file is a text note or a feature film. Three properties matter. The same file always gives the same hash. Changing even one byte gives a completely different hash. And the process is one-way, so you cannot rebuild the file from its hash.

That makes a hash useful for checking that a download is intact, that two copies are identical, or that a file has not changed since you last hashed it. You can see this yourself with our bulk SHA-256 hash manifest tool, which hashes files in your browser without uploading them, or compare two files with the file comparison checker.

A hash says nothing about when the file was created, who made it, or whether its contents are accurate. It also only matches the exact bytes: re-saving a photo or exporting a document again usually produces a different hash even if it looks the same. Older algorithms such as MD5 and SHA-1 are no longer considered safe against deliberate collisions; see MD5 and SHA-1.