scriptiii
100% Client-Side

AES-256-GCM · PBKDF2

AES-256 encrypt and decrypt

Encrypt text with a passphrase using AES-256-GCM and PBKDF2 key derivation, or decrypt a payload this tool produced — entirely in your tab.

PBKDF2-SHA-256 · 210,000 iterations · AES-256-GCM

Used only in this tab. There is no recovery if it is lost.

Hashed as UTF-8.

Keys are derived and used inside this tab with WebCrypto. The passphrase and the plaintext are never transmitted, logged or stored — which also means a forgotten passphrase cannot be recovered.

Short answer: choose Encrypt, type a passphrase of at least eight characters and the text, then press the button. You get a self-contained payload starting withsiii1. that carries its own salt, IV and iteration count. To read it back, switch to Decrypt and paste both the payload and the same passphrase.

What the payload contains

Nothing is hidden about the format, and that is fine: AES-GCM is secure even when everything except the key is public. The salt and IV are not secrets; the passphrase is.

Limits worth knowing

A passphrase typed into a web page can be captured by a malicious extension or a compromised device, and this page cannot detect either. It protects the payload in transit and at rest, not the machine it was typed on. For high-value keys, encrypt on a machine you control with a dedicated tool.

Encryption questions

How strong is this encryption?

The construction is AES-256-GCM, the same authenticated cipher TLS uses, with a key derived from your passphrase by PBKDF2-SHA-256 at 210,000 iterations and a fresh 16-byte salt. The weak point is always the passphrase, not the cipher: an eight-character password can still be guessed offline.

Can I decrypt a payload from another tool?

No. The format is specific: siii1.iterations.salt.iv.ciphertext. Other tools derive keys or frame data differently, so a payload from elsewhere fails with a clear message rather than decrypting to garbage. Use the same tool for both directions.

What happens if I forget the passphrase?

The data is gone. There is no recovery key, no account and no server copy — the passphrase is the only key, and it is never stored or transmitted. Keep it in a password manager before you close the tab.

Why does a wrong passphrase give the same error as a modified payload?

Because GCM authenticates the ciphertext. A wrong key produces a tag mismatch, and so does a single flipped bit; the cipher cannot tell you which happened. The tool says both possibilities instead of pretending to know.

Is this a replacement for a password manager or GPG?

No. It is for a one-off: encrypting a note, a token or a config snippet before sending it through a channel you do not fully trust. For files, keys and long-term secrets use a tool designed for it, such as age, GPG or your OS keychain.

Related tools

Hash generatorA digest verifies; it does not hide.Base64 encoder and decoderEncoding is not encryption.Random string generatorA strong passphrase to start from.All developer toolsEvery tool in the developer group.