What encoding is this?
Paste any string. It is identified and decoded as you type, layer by layer: Base64, hex, binary, URL, HTML entities, JWT, ROT13, hashes and mojibake.
The answer appears here as soon as you paste. Nothing leaves your browser unless you press Explain.
An AI model names where the string likely came from and walks through the evidence. Shortcut: Ctrl/⌘ + Enter. Don't paste live passwords or keys.
Reading the clues yourself
- Alphabet. Only 0/1 is binary; 0–9 a–f is hex; A–Z a–z 0–9 + / = is Base64.
- Length. Base64 comes in multiples of 4. Hex in pairs. Binary in groups of 8. Fixed lengths of 32, 40 or 64 hex characters are hashes: check them with the hash identifier.
- Markers.
%means URL encoding;&…;means HTML entities;\umeans string escapes;Ãandâ€mean mojibake. - Prefixes.
eyJis Base64 for{", so it starts almost every JWT.data:is a data URI.0xis hex.
Questions people ask
How can I tell what encoding a string uses?
Look at the alphabet and length. Only 0 and 1: binary. 0–9 and a–f in pairs: hex. Letters, digits, + and / with length a multiple of 4, maybe ending in =: Base64. %XX sequences: URL encoding. &name; patterns: HTML entities. Starts with eyJ and has two dots: a JWT. This page checks all of these at once.
Can it decode a hash like MD5 or SHA-256?
No tool can. Hashes are one-way: a 32-character hex string is usually MD5, 40 is SHA-1, 64 is SHA-256. You can only hash a candidate and compare, which the hash identifier does in your browser.
What if the string is encoded more than once?
Strings are often wrapped in layers, for example Base64 inside URL-encoding, or hex of Base64. The decode chain at the top keeps peeling the most confident layer until plain text comes out, and shows each step.
Does it identify ciphers like Caesar or ROT13?
It spots ROT13 and other Caesar shifts in English text by trying all 25 shifts and checking for common words. It does not break keyed ciphers such as Vigenère or real encryption such as AES: encrypted data looks like random bytes, and the page will say nothing readable came out.
What does “eyJ” at the start of a string mean?
eyJ is what {" becomes in Base64, so the string is Base64-encoded JSON. Three such parts joined by dots make a JSON Web Token (JWT).
What does the AI explanation add?
The instant checks tell you which decoders succeed. The explanation (sent only when you press the button) looks at the whole string, names likely sources such as a cookie, JWT or data URI, spots nested layers and flags strings that look like secrets.
Is my string stored?
The instant checks run only in your browser. If you ask for an explanation, the string (up to 2,000 characters) is sent to our server and an AI model through Vercel AI Gateway to generate the answer; we do not store it. Don’t paste live passwords or API keys.