If you forget the passphrase, I cannot help. That is the product.
Use this when you want to turn a blob of text into ciphertext you can park in email or a gist without the plaintext sitting next to it: a staging token, a recovery phrase you will also write on paper, a note to your future self on another machine. Encryption is AES-GCM via Web Crypto. The passphrase is stretched with PBKDF2 (SHA-256, 100,000 iterations), with a 16-byte salt and a 12-byte IV packed in front of the ciphertext and then Base64’d. There is no account, no reset email, no “forgot password.” Forgotten passphrase means the bytes are gone.
This is not a vault against malware. A keylogger still sees the passphrase. A browser extension can still read the plaintext field. Shared Zoom still sees the screen. AES-GCM protects the file you download after you encrypt, assuming the passphrase never leaked. It does not protect the minute you typed the secret. For real team secrets, use a secrets manager. For a password you will use daily, use a password manager. This page is a notepad with a lock icon, and I would rather you treat it that way than tattoo “AES-256” on an incident report.
Worked example: an 80-character staging token
Plaintext is an 80-character API token. Passphrase is 20 random characters from the password generator, stored in your manager. The UI refuses passphrases under 8 characters; that is a floor, not a recommendation. 8 lowercase letters as a wrapping passphrase around an 80-character token is how you undo the token’s entropy. Encrypt, download encrypted.txt, put the passphrase in the manager next to the environment name. Decrypt later on this page with the same passphrase. If decrypt fails, it is almost always a truncated Base64 copy or the wrong passphrase, not “AES broke.”
Worked example: you forget the passphrase in week two
There is no recovery. I do not have your passphrase. I do not have a backup. PBKDF2 at 100,000 iterations plus AES-GCM means guessing “Summer2026” is plausible and guessing a 20-character random string is not. If the note was a crypto seed phrase and the passphrase lived only in your head, you now have an expensive lesson. Write the passphrase in the same manager that holds the related logins, or do not encrypt something you cannot afford to lose. Paper backup of a seed is still paper; encrypting it and losing the wrapper password is not an upgrade.
Worked example: the machine was already sick
You encrypt a recovery code on a laptop with a stealer. The ciphertext is fine. The plaintext and passphrase were typed into fields the stealer already hooks. AES did not fail. The threat model did. Same class: encrypting in a tab with seven “coupon” extensions, then pasting ciphertext into email as if the metadata (filename encrypted.txt, time, recipient) were free. Ciphertext can travel. The passphrase should not travel in the same message. “AES-256” on a marketing badge does not mean I audited this against a nation-state. Read View source. Use a manager for anything you would call production.
What this will not do
It is text, not a file locker for 2 GB videos. It is not deniable encryption, not a team sharing workflow, not a replacement for 1Password or Bitwarden. Confirm-password mismatches fail closed. If you encrypt twice with two passphrases, you now have two ciphertexts and two ways to forget. Clear the plaintext field when you are done. Close the tab on a shared computer. I still cannot reset your passphrase after that, which remains the feature.
Questions
What algorithm is this?
AES-GCM, 256-bit, via Web Crypto. Passphrase → PBKDF2-SHA-256, 100,000 iterations, 16-byte salt, 12-byte IV. Confirm in View source.
I forgot the passphrase. Can you decrypt it?
No. There is no reset. Forgotten passphrase means the ciphertext is gone. That is the design.
Does AES-GCM stop malware on my PC?
No. A keylogger or a malicious extension still sees what you type. This protects the downloaded ciphertext, not the minute you typed the secret.
Why is 8 characters the minimum?
A UI floor so empty and tiny passphrases bounce. Use a long random passphrase from a manager. 8 lowercase letters is still a bad wrapper.
Can I share the ciphertext with a teammate?
You can send ciphertext. You still need a separate channel for the passphrase. For team secrets, use a secrets manager, not this notepad.
Will this encrypt a 200 MB file?
It is a text box. Large files need a dedicated local tool. Pasting megabytes of Base64 into a textarea is how tabs die.