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. Here that happens in your browser via the Web Crypto API. Our servers are not involved at any point.

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?

Files up to 10 MB are supported. Larger files are rejected with a message. The File API reads the file directly from disk, and hashing a large file may take a few seconds depending on your device.

SHA-256 File Hash Without Uploading

Generate a SHA-256 checksum for any file up to 10 MB without uploading it. Drop the file and the Web Crypto API hashes its bytes in this tab, then paste a published checksum under the result to see whether the two values match.

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. 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.

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 yourself in 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 digital signatures, TLS certificates, and HMAC. Stored passwords need a slow, salted function such as bcrypt, scrypt, or Argon2 rather than a single SHA-2 hash.

Output size: 256 bits (64 hex characters)
Standard: FIPS PUB 180-4 (NIST)
Browser API: SubtleCrypto.digest()
Security status: Approved for integrity, signatures, and HMAC

Related operations

To turn text into a reversible encoding rather than a one-way fingerprint, use the Base64 encoder. To generate strong random secrets to hash, use the password generator. For random unique identifiers, 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. Here that happens in your browser via the Web Crypto API. Our servers are not involved at any point.
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?: Files up to 10 MB are supported. Larger files are rejected with a message. The File API reads the file directly from disk, and hashing a large file may take a few seconds depending on your device.

Last reviewed September 30, 2026

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