Decrypt File
AES decryption.
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How decryption works
Decryption reverses encryption using the same key. The encrypted file carries the parameters needed to rebuild that key from your password — the salt, the initialisation vector, and the iteration count — while the password itself is stored nowhere. That is why the file can be decrypted anywhere, by any compatible tool, but only by someone who knows the passphrase.
Authenticated encryption modes such as AES-GCM add an integrity tag, so decryption either succeeds and returns exactly the original bytes, or fails outright. There is no partially correct result. A failure means one of two things: the password is wrong, or the file has been altered or corrupted in transit. It never means the tool is guessing — and no tool can recover the contents without the password, no matter how it is marketed.
Why we built this tool
You decrypt to open something you or a colleague protected earlier: an archived document, a file sent by a client, a backup, or something carried on a USB stick.
Handing an encrypted file plus its password to a web service means giving a stranger everything needed to read your data — the exposure is total, and it is worse than sending the plaintext, because you also reveal the passphrase you may have used elsewhere. Ours decrypts in your browser with the Web Crypto API, so both file and password stay in your tab. No upload, no transmission, no logging, and no size limit beyond your own memory.
Tips and common mistakes
- A failure means a wrong password or a damaged file; there is no partial decryption.
- Check for a trailing space if you pasted the passphrase from somewhere.
- Delete the decrypted copy when you have finished with it — it has no protection at all.
- Files transferred over unreliable channels can corrupt; compare sizes if decryption fails unexpectedly.
Quick start: using Decrypt File
- Load the encrypted file.
- Enter the passphrase used to encrypt it.
- Run the decryption; failure means a wrong password or a damaged file.
- Open the decrypted file to confirm the contents are intact.
- Delete the plaintext copy when you have finished with it.
To protect a file in the first place, use Encrypt File. For PDFs specifically, Unlock PDF handles document passwords.