Base64 Encoder/Decoder - Encodage et décodage Base64

Base64 is everywhere binary data has to slip through text-only channels: email attachments, data URIs in CSS, JSON fields, auth headers, JWT tokens. And every time you have one of those strings in front of you, all you really want is to know what is inside. That is exactly what this tool is built for: one input, one click, the plain-text result.

It does more than plain Base64. Five encodings are on tap - classic Base64, URL-safe Base64URL (with - and _ instead of + and /), Base32, percent-based URL encoding and hex. In both directions. Paste an encoded string and the auto-detection usually works out the format on its own and flips straight to decode.

Files get their own modes. Drop an image or any file up to 50 MB and you get the Base64 string back - or a ready-made data URI you can embed directly into HTML or CSS. The other way round, the file decoder turns a Base64 blob back into a real downloadable file. If it is an image, you see a preview instantly, whichever mode you are in.

The JWT trick is the quiet favourite for anyone working with APIs. Paste a JSON Web Token and decode it as Base64URL, and the tool automatically pulls out the payload and shows it cleanly formatted as JSON. No copying the middle segment by hand, no separate debugger needed.

Everything runs purely in the browser. TextEncoder and TextDecoder make sure umlauts, emojis and other UTF-8 characters survive the round trip intact - no mangled a-umlaut, no broken euro sign. Your data, your tokens, your files stay on your device. No server round trip, no upload, no log.

The presets keep everyday work quick: encode text, decode a JWT, build a Basic Auth header, URL-encode, image to data URI - one tap sets mode, encoding and direction. Plus stats on characters, bytes and size growth so you can see how much Base64 inflates your data (rule of thumb: about a third bigger).