Base64 Decoder

Convert Base64-encoded strings back into their original plain text or binary representation.

Base64 Decoder

Convert Base64 encoded text back to plain text.

Base64 Input

Decoded Text

About Base64 Decoding

Base64 decoding converts Base64-encoded text back to its original form.

Input requirements:

Only valid Base64 characters: A-Z, a-z, 0-9, +, /
Optional padding with = or == at the end
Whitespace is automatically removed

What is Base64 Decoding?

Base64 decoding is the reverse of encoding — it transforms a Base64 string back into the original binary or text data. The decoder reads groups of four Base64 characters and reconstructs three bytes of original data, stripping any trailing = padding characters in the process.

Valid Base64 input uses only the characters A–Z, a–z, 0–9, +, and /, with optional = padding at the end. Providing invalid characters will result in a decoding error.

Common Use Cases

Inspecting JWT Tokens: Decode the header and payload segments of a JSON Web Token to read the claims without a library. Extracting Embedded Images: Retrieve the raw binary of an image that was inlined as a data URI in HTML or CSS. Debugging API Responses: Decode Base64-encoded fields returned by APIs to inspect the underlying binary content or credentials. Email Forensics: Decode MIME-encoded email attachments or body parts to recover the original file content.

Tips

Ensure the input has correct padding; some implementations omit trailing = characters, which may need to be re-added before decoding. If the encoded string came from a URL, replace - with + and _ with / before decoding with the standard Base64 alphabet. Decoding produces raw bytes — if the original data was text, confirm the character encoding (typically UTF-8) to interpret it correctly.