Compute cryptographic hash digests for files of any size using streaming WebCrypto operations with progress tracking.
Pick a file from disk, choose a digest algorithm, and this tool streams the file through the browser's WebCrypto engine, showing progress as it goes, then returns the hash as a hexadecimal string. Because it reads the file in chunks rather than loading it whole, files of many gigabytes hash without exhausting memory, and the file never leaves your machine. The thing most people get wrong: the digest covers the exact bytes only. Renaming the file changes nothing, but a single added newline - which your text editor may insert silently - changes the entire digest.
A concrete input and expected output from the current implementation.
Input
A text file whose contents are exactly the five ASCII bytes "hello" with no trailing newline (for example, created with printf 'hello' > example.txt).
Expected output
SHA-256 = 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824 (5 bytes hashed, progress 100%)
SHA-256 output is always 64 hex characters (256 bits) regardless of input size, and this value is the digest of the five bytes h-e-l-l-o. Add a single newline and the entire digest changes - which is exactly why download pages publish hashes.
The file is read from disk in pieces, and each piece is fed into the hash state as it arrives, so the whole file is never held in memory at once; a 10 GB file costs about the same memory as a 1 KB one. The progress figure is bytes read divided by the file's total size, updated per chunk, and the digest is finalized only when the last byte has been processed.
The digest's length is set by the algorithm, not the file: SHA-256 always produces 64 hex characters (32 bytes), SHA-384 produces 96, SHA-512 produces 128. Only the file's content bytes enter the calculation - name, folder, timestamps, and permissions are ignored - so two files that differ in name but not content produce identical digests.
Almost always a byte mismatch rather than a tool error: the published digest may be for a different version of the file, or the two sides differ in line endings, encoding, or a trailing newline - common after saving on Windows, where editors often convert line endings to CRLF. Re-download the file and confirm both sides used the same algorithm.
No. The file is read within your browser and hashed locally using the Web Crypto API; nothing is transmitted, so the calculation works offline too. If you want to confirm, disconnect the network after the page loads and hash a file - it completes exactly the same.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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