Private browser tool

SHA-256 file checksum calculator

Calculate and compare a file’s SHA-256 checksum without uploading the file. Large files are read in small chunks so they do not need to be loaded into memory all at once.

Calculate a checksum

Your file stays on your device
The calculator reads it locally. No file content or checksum is sent to Filekub.
Drop a file here

or select one from your device

Choose a file to begin. SHA-256 is the only algorithm used.

What is a SHA-256 checksum?

SHA-256 turns file contents into a 256-bit digest, normally displayed as 64 hexadecimal characters. Changing even one byte produces a different digest. Software publishers often provide a checksum beside a download so you can compare your copy with the file they intended to distribute.

This tool implements SHA-256 incrementally in a Web Worker. The browser reads one 4 MB slice at a time, allowing practical use with large files while keeping the page responsive. Calculation speed depends on your device and browser.

How to compare checksums safely

Copy the expected SHA-256 checksum from the publisher’s official HTTPS website, release page, or another channel you already trust. Select your downloaded file, then paste the expected value into the comparison field. Compare all 64 characters—not just the beginning or end.

Interpret the result carefully. “Match” means the selected file produced the same SHA-256 value. “No match” can indicate a damaged, incomplete, modified, or simply different version of the file. Delete an unexpected file and obtain a fresh copy from the official source.

Privacy and browser support

Hashing occurs in your browser. Selecting a file gives this page temporary permission to read that file; it does not expose other files. The calculator itself makes no upload request. Closing or refreshing the page clears its current result.

A current browser with JavaScript, Web Workers, Blob.arrayBuffer(), and BigInt is required. The result is deterministic: identical bytes produce the same SHA-256 value on every conforming implementation.

Frequently asked questions

Can I check a very large file?

Yes, subject to your browser and device limits. The tool processes 4 MB chunks instead of reading the entire file into memory. Keep the tab open until calculation completes.

Why is my checksum different?

Confirm you selected the same release and platform as the published checksum. A partial download, repackaged archive, line-ending change, or any other byte difference changes SHA-256.

Does a match mean the file is safe?

No. It confirms only that the file matches the expected checksum. The expected checksum and file could both come from an untrusted or compromised source.

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