Put a Password on Any File
You want a file that asks for a password before it opens — a contract, a spreadsheet, a folder of photos. The honest way to deliver that is encryption: this tool locks any file with a password using AES-256, right in your browser, with nothing uploaded. You do not need to understand cryptography to use it; you just need a good password.
The actual tool runs in our ad-free secure workspace — nothing on this page processes your file.
Open Encrypt a File →What this tool does
- Locks any file type — PDF, Word, Excel, photos, videos, anything — behind a password of your choosing.
- Uses real encryption (AES-256-GCM) rather than a removable 'protection' flag, so the lock cannot simply be stripped off.
- Stretches your password with PBKDF2-HMAC-SHA-256 (600,000 iterations) so guessing attacks are slow and expensive.
- Detects tampering: if anyone modifies the locked file, unlocking fails with a clear error instead of opening altered content.
- Optionally issues a one-time recovery key — a spare key in case you forget the password.
- Never uploads anything: the file, the password, and the result all stay on your device.
Your privacy on this tool
Stays on your device
- Your file is locked (encrypted) entirely within your browser.
- The password you type is used on-device only and is never transmitted or logged.
- The protected file saves directly to your computer — we never receive a copy.
Reaches our server: nothing
This tool makes no upload. Your content is processed entirely in your browser.
How to use it
- Head to the tool at /app/encrypt-file.
- Drop in the file you want to password-protect.
- Type a password — longer is better, and the strength meter will warn you if it is guessable.
- Optionally save the offered recovery key somewhere safe, in case you forget the password later.
- Click to protect the file and download the locked .svault version.
- Share the password with the recipient by a separate channel — a phone call or a different app, never the same email as the file.
Common uses
- Emailing a lease, offer letter, or contract that should not be readable if the email is forwarded or breached.
- Handing your accountant tax documents on a USB drive that could be lost or misplaced.
- Protecting a folder of family photos before putting them on a shared computer.
- Sending payroll or HR files to a colleague over a chat tool you do not fully trust.
- Storing a copy of your ID documents in a cloud drive without trusting the drive's own security.
Supported formats
- Any file type as input
- Output: SecretPNG vault (.svault)
Works in every up-to-date mainstream browser — Chrome, Edge, Firefox, and Safari — on desktop and mobile.
Limitations & security notes
Limitations
- Forget the password and lose the recovery key, and the file is gone for good — real protection cuts both ways, and no one can reset it.
- The recipient opens the file with the free decryption tool on this site (or any .svault-compatible software); it does not prompt for a password all by itself like some PDF files do.
- A weak password undermines everything — 'password123' falls in seconds regardless of the encryption behind it.
- This is a beta product and has not yet been independently audited.
Security notes
- Many 'password protect' features (old Office formats, ZipCrypto ZIPs) are weak locks that tools can strip in minutes — genuine encryption like AES-256 is what actually delivers the protection people assume they are getting.
- The password is the whole game: a six-word passphrase from our passphrase generator is both memorable and very hard to crack.
- Send the file and its password by different routes. If both travel in one email, anyone who reads the email gets both.
- Tamper detection is built in — a locked file that has been altered in transit will refuse to open rather than open incorrectly.
- For a folder full of files, consider the encrypted vault tool, which also hides filenames.
Frequently asked questions
- How is this different from password-protecting a PDF or Word file directly?
- Office and PDF password features vary wildly: modern versions can be solid, but older formats and 'restrict editing' modes are notoriously easy to strip. This tool applies uniform AES-256-GCM encryption to any file type, with key stretching and tamper detection, so you get one predictable level of protection instead of format-by-format roulette.
- Will the person I send it to need special software?
- They open it with the free decryption tool on this site — it runs in their browser, no install or account needed. You send them the .svault file and, separately, the password. The format is openly documented, so other compatible tools can open it too.
- Can someone just remove the password?
- No. There is no password 'flag' to remove — the file's contents are mathematically transformed with AES-256, and without the key derived from your password the data is indistinguishable from random noise. The only attack is guessing the password, which is why choosing a strong one matters.
- What if I forget the password?
- If you saved the optional recovery key when protecting the file, use it to unlock. Otherwise the file is permanently unrecoverable — we cannot reset it because we never had the password or the file. Take the recovery key option seriously for anything important.
- Is it really free? What is the catch?
- The tool is free and the protection runs on your own device, which costs us almost nothing per use. SecretPNG is in beta; the honest caveats are that it has not been independently audited yet, and you carry the responsibility of remembering your password.
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Last reviewed: 2026-07-14Open Encrypt a File
SecretPNG is in beta and has not been independently audited. Security status.