Developer Tools
Base64 Decoder
Decode Base64 back into text or binary, in your browser. Data URLs (data:image/png;base64,...) are recognised automatically and offered as a downloadable file. Standard and URL-safe alphabets are both supported.
Your input is processed locally in your browser. It is not uploaded to Dueneo.
Loading Base64 Decoder…
How to use
- 1
Paste your Base64 string
Drop a standard or URL-safe Base64 string. A data: URL prefix is detected automatically.
- 2
Click Decode
The decoder first tries UTF-8 text. If the bytes are not valid UTF-8 it falls back to binary.
- 3
Read or download
Text appears in the output box with a Copy button. Binary content shows a Download button so you can save the original file.
- 4
Reset to try again
Click Reset to clear everything and paste a new value.
Common use cases
- Read the contents of a data URL embedded in HTML or CSS.
- Recover a binary file from a Base64-encoded API payload.
- Decode a JWT payload (the middle segment is Base64URL).
- Inspect what a Base64 string actually contains.
Limitations
- Inputs larger than 1 MB are rejected to keep memory usage safe.
- The decoder does not verify signatures on JWTs — it only reveals the plaintext payload.
- Whitespace inside the Base64 string is stripped before decoding.