Need to send a tax return, a contract or a folder of scans and want only the right person to open it? You can encrypt the file with a password right in your browser. Nothing is uploaded and you don't need an account.
The quick way: Potent Cipher's free Encrypt tool
- Open Encrypt a file.
- Drop in the file (or click to choose one). Any type works: PDF, DOCX, JPG, ZIP, video.
- Type a passphrase. Make it long: four or five random words beat a short, clever password. See how to make a strong password you can remember.
- Click Encrypt. Your browser makes an encrypted copy ending in .pcipher and saves it.
- Send or store the .pcipher file. Send the passphrase separately: a different app, a phone call, or a one-time secret link.
To open it, the other person drops the .pcipher file on the same page and types the passphrase. The original file comes back, byte for byte.
Why "in your browser" matters
Many "encrypt file online" sites upload your file, encrypt it on their server and send it back. That means your unencrypted file sat on someone else's computer. Here the encryption runs on your device (WebAssembly in your browser), so the file never leaves it. You can even disconnect from the internet after the page loads.
What protects the file
- Argon2id turns your passphrase into a key. It is deliberately slow and memory-hungry, so trying billions of guesses is impractical.
- XChaCha20-Poly1305 encrypts the contents in chunks and adds a tag to each one, so any change or truncation is detected instead of silently giving you a broken file.
- The .pcipher format is published, so the file isn't tied to us: anyone can build a tool that opens it.
Other ways to password-protect a file
- ZIP or 7-Zip with AES-256. Works well if both people have the tool; avoid the old "ZipCrypto" option, which is weak.
- PDF passwords in Acrobat or similar. Fine for PDFs only; the strength depends on the settings used.
- Office "Encrypt with password" for Word and Excel. Modern versions are strong; older formats are not.
The browser tool's advantage: it works for any file type, on any computer, and the recipient doesn't need special software.
Keep encrypted files in your vault
On the Pro plan you can upload files to your Potent Cipher vault. They are encrypted on your device the same way before upload, and only your devices can open them.