Encrypt files in your browser with AES-256
Lock a file behind a password using authenticated AES-256-GCM encryption that runs entirely on your device. The file never leaves your browser — there is no server to upload to.
Open this tool in FileX →How it works
- Open the Encrypt tool and drop in the file you want to protect.
- Choose a strong password. FileX derives a 256-bit key from it with Argon2id (memory-hard, 64 MiB) and a random salt.
- Download the encrypted
.filexcontainer (the quantum-safeFXQ1format, single file or multi-file archive). - Share the container over any channel; send the password separately. Only someone with the password can open it.
Why encrypt files locally instead of in the cloud
Most "secure" file services encrypt after your file reaches their servers, which means the plaintext still travels the internet and sits on someone else's disk. FileX encrypts before anything leaves your machine using the browser's built-in Web Crypto API. No upload, no account, nothing to breach.
What is a .filex file
A modern .filex container uses the FXQ1 format: an authenticated header plus the file encrypted in 4 MiB AES-256-GCM chunks, so even multi-gigabyte files encrypt without exhausting memory. Any tampering — a flipped bit, a reordered or truncated chunk, or a wrong password — is rejected on decrypt rather than silently returning garbage. Files made by older FileX versions (FLX1/FLX2) still open.
Is AES-256 safe against quantum computers
Yes. AES-256 is already quantum-resistant — Grover's algorithm only halves its effective strength, leaving ~128-bit post-quantum security. The quantum threat is to asymmetric key exchange, which is why FileX's recipient mode adds ML-KEM-768. Password encryption needs no such change.
Frequently asked questions
Is my file uploaded anywhere?
No. All encryption happens in your browser via the Web Crypto API and audited pure-JS libraries. The live monitor at the bottom of the page shows 0 bytes uploaded, and the strict Content-Security-Policy blocks any third-party request.
What encryption does FileX use?
AES-256-GCM (authenticated encryption) with a key derived from your password using Argon2id (m=64 MiB, t=3, p=1) and a random per-file salt. Argon2id is memory-hard, which makes password-guessing far more expensive than older KDFs. All standard, audited primitives — no hand-rolled crypto.
What happens if I forget the password?
The file cannot be recovered. There is no backdoor, no reset, and no copy of your key anywhere — that is the point. Store the password in a password manager.