What this tool decrypts
This tool reverses the output of the matching Encrypt Text tool on this site. It does not decrypt arbitrary data. The input must be a Base64 string in the format that tool produces, which is made of three parts joined together: a 16 byte random salt, a 12 byte initialization vector, and the encrypted data.
Decryption uses AES-256-GCM. Your passphrase is stretched into a 256-bit key using PBKDF2 with SHA-256 and 100,000 iterations, using the salt stored at the front of the text. GCM mode also checks integrity, so if the passphrase is wrong or the text has been altered, decryption fails outright rather than returning garbled output.
When you would use it
You use it when you or someone else previously encrypted a note, a snippet, or a short message with this site's encryption tool and now need the original wording back. Typical examples are an encrypted message you stored in a notes app, text you sent to a colleague who shares the passphrase, or a small value you wanted to keep out of plain view.
Text that was produced by other software will usually not work, even if it is also AES, because the layout and key derivation need to match exactly. Likewise, encrypted files are not handled here, only text.
For choosing a passphrase to begin with, the Password Generator can create a long random one, which is far harder to guess than a short phrase.
Use decryption responsibly. Only decrypt text that belongs to you or that you have been given permission to read. This tool cannot break a passphrase you do not know, and it is not designed to.
How to decrypt text with this tool
- Paste the encrypted Base64 text into the Encrypted text (Base64) box. Surrounding spaces and line breaks at the ends are trimmed.
- Type the passphrase into the Passphrase field. It is hidden as you type.
- Click Decrypt.
- If the passphrase and text are correct, the original message appears under Result.
- Click Copy to copy the result to your clipboard.
If you leave the passphrase empty, the tool asks you to enter one. If decryption fails, it shows a message suggesting that you check your passphrase and confirm the text was copied in full.
Troubleshooting and good habits
Most failures come from one of three things. The passphrase has a typo, a different capital letter, or an extra space. The encrypted text was cut short when copied, since even a single missing character at the end breaks it. Or the text was not created by this site's encryption tool in the first place.
There is no recovery option. The passphrase is never stored, and with a wrong one the data stays unreadable. Keep passphrases in a place you trust, such as a password manager.
All of this runs in your browser using the built-in Web Crypto API. Neither the passphrase nor the text is sent to a server. Still, decrypted text appears on your screen and can be copied to the clipboard, so avoid doing this on a shared or untrusted computer.