How can I verify the file isn't uploaded?

Open your browser's DevTools (F12) and go to the Network tab. Hash a file while watching for requests. No outbound connections appear because all hashing happens locally in your browser tab using the built-in SubtleCrypto API.

Why hash files without uploading?

The hash itself is a fingerprint, but to compute it the entire file must be processed. Doing that in the browser via the Web Crypto API means the bytes never leave your device just to verify integrity.

What can I use a SHA-256 hash for?

Compare a file's hash against a value published by the software author to confirm you downloaded the correct, unmodified file. You can also verify that a file has not been altered after it was sent to you.

Does this work with large files?

Yes. The File API reads the file directly from disk. Large files may take a few seconds to hash depending on your device, but there is no hard size limit.

SHA-256 File Hash Without Uploading

Generate a SHA-256 checksum for any file entirely in your browser. All processing runs in your browser. Drop your file and the hash is computed locally using the Web Crypto API built into your browser.

Drop a file

Drop any file here

or click to browse. All processing is local

ALGORITHM

DISPLAY

Drop any file to generate its checksum. Compare against a publisher's hash to verify integrity.

Processed locally

How it works

Dropping a file reads its bytes into memory through the File API without involving any upload. Those bytes are then handed to crypto.subtle.digest('SHA-256'), producing a 256-bit digest shown as 64 hex characters. The whole operation happens inside this browser tab with no upload step.

Processing runs in your browser

Your file is read directly by the browser. All hashing happens locally, our servers are not involved at any point. You can verify this yourselfin your browser's DevTools Network tab.

Technical specification

SHA-256 is specified in FIPS PUB 180-4 (NIST, 2015). SHA-256 produces a 256-bit (32-byte) digest encoded as 64 hexadecimal characters. Both are part of the SHA-2 family and remain approved for all security applications including TLS certificates, code signing, and HMAC construction.

Output size: 256 bits (64 hex characters)
Standard: FIPS PUB 180-4 (NIST)
Browser API: SubtleCrypto.digest()
Security status: Approved, recommended for all uses

Related operations

For encoding the result as Base64 for transport, try Base64. To generate strong random secrets to hash, use the password generator. For random unique identifiers without a hash collision risk, see the UUID generator.

Frequently asked questions

How can I verify the file isn't uploaded?: Open your browser's DevTools (F12) and go to the Network tab. Hash a file while watching for requests. No outbound connections appear because all hashing happens locally in your browser tab using the built-in SubtleCrypto API.
Why hash files without uploading?: The hash itself is a fingerprint, but to compute it the entire file must be processed. Doing that in the browser via the Web Crypto API means the bytes never leave your device just to verify integrity.
What can I use a SHA-256 hash for?: Compare a file's hash against a value published by the software author to confirm you downloaded the correct, unmodified file. You can also verify that a file has not been altered after it was sent to you.
Does this work with large files?: Yes. The File API reads the file directly from disk. Large files may take a few seconds to hash depending on your device, but there is no hard size limit.