This is a single-page browser tool built around a concept borrowed from classic espionage: the newspaper code. The idea is that a secret message is hidden inside a perfectly ordinary piece of public text, and only someone with the right key can extract it. No invisible ink required.
It is a variation on the Vigenère cipher, but with a twist that I found more interesting than the traditional approach. Rather than encrypting nonsense into nonsense, Decodedly is designed so that both the cover text and the hidden message are real, readable, meaningful content. A news article concealing a private note. A public announcement hiding something else entirely. The cover text just has to be longer than the secret.
To hide a message you paste in your cover text and your hidden message, generate a key, and share either the key or the generated link with whoever needs to read it. To decode, you paste the cover text, drop in the key, and the hidden message appears. The whole thing runs in the browser with nothing sent anywhere.
It is a small, self-contained thing. Genuinely useful for anyone who enjoys the idea of communicating privately in plain sight, and probably quite good fun even if you do not.
Copy this text and try this: https://tinyurl.com/4z9e56fw 😉