File Checksum Calculator — MD5, SHA-1 & SHA-256
Generate MD5, SHA-1 and SHA-256 checksums for any file — entirely in your browser. Drag a file in (or paste text) and this tool computes all three digests instantly, with nothing uploaded and nothing stored.
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Drop a file here, or to compute its checksums.
Hashing happens in your browser — nothing is uploaded or stored.
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Why checksums matter
A checksum is a short, fixed-length fingerprint computed from a file's contents. Change a single byte in the file and the checksum changes completely. That makes a checksum a fast way to confirm a transfer worked: your source publishes a checksum, you download the file, compute it again with the same algorithm, and if the two match you know the file arrived byte-for-byte complete. This is the same idea behind the hashes nearly every download page uses today — it is how you catch a truncated transfer, a corrupted package, or a deteriorating drive before the bad file causes real problems.
How this checksum calculator works
This tool uses the browser's own file-reading and cryptography capabilities — the File and FileReader APIs to open the file you choose, and crypto.subtle.digest to compute the SHA-1 and SHA-256 checksums with your browser's built-in, hardware-accelerated crypto. Because the Web Crypto standard does not expose MD5, that digest is computed by a small self-contained JavaScript implementation of RFC 1321. The file is read into memory once and all three checksums are derived from that single read, so hashing is fast and consistent. The result is displayed as lowercase hex, ready to compare, and each hash has its own copy button.
Honest note: your file never leaves your device
Everything on this page happens in your browser. There is no server call, no upload, and no background storage: the file you select is read locally, hashed locally, and then discarded when you leave or refresh. No credentials are involved, nothing is logged, and we collect no data from this tool. The only result you see is the checksum on the screen.
Limits to keep in mind
Hashing is CPU-bound, so very large files (or huge amounts of pasted text) may take a moment — the tool shows a short "hashing…" state and the elapsed time so you know it is working. MD5 and SHA-1 are still widely used for integrity checks, but they are no longer considered secure for cryptographic security. For security-sensitive uses, prefer the SHA-256 checksum. And because everything runs locally, this tool is unaffected by your connection speed; only your device's processor matters.
Frequently asked questions
Is my file uploaded to compute its checksum?
No — hashing runs entirely in your browser. SHA-1 and SHA-256 use the browser's built-in Web Crypto API, and MD5 is computed by a small local script, so your file never leaves your device and is never uploaded or stored anywhere.
Which checksum algorithms are supported?
MD5, SHA-1 and SHA-256. All three are computed in a single pass from the same file and shown at once, so you can compare against whichever checksum your source publishes.
Why would I need a checksum?
A checksum is a short fingerprint of a file's contents. Comparing the checksum of the file you downloaded to the checksum your source publishes confirms the file arrived complete and uncorrupted — or warns you if it did not.
Start using the free checksum calculator
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Want to know exactly how the app handles your data? Read the security page and the privacy policy.