Base64 Decode

Decode Base64 online

Base64 represents arbitrary bytes as printable text by mapping each six-bit value to one character. Standard Base64 and the URL-safe alphabet are specified by RFC 4648. This tool converts encoded text back to bytes and then displays those bytes using the selected output encoding.

How to use the decoder

Paste the encoded value and select Standard for the common +/, URL-safe -_, or IMAP-style +, alphabets. The standard decoder accepts omitted trailing padding and ignores CR/LF line wrapping. Choose Custom only when the source uses a different 64-character alphabet. Select UTF-8 for ordinary text or Hex to inspect exact binary bytes.

Example

The standard Base64 value SGVsbG8= decodes to Hello in UTF-8. The bytes fbff encode as +/8= in standard Base64 and -_8= in Base64URL; both are accepted by this page’s Standard decoder.

Important limitations

Base64 is encoding, not encryption, and provides no secrecy or integrity. This page rejects characters outside its supported alphabets except CR/LF. A valid Base64 string can still represent unsafe or non-text data, and decoding binary bytes as text can display replacement characters.

Frequently asked questions

Why is the decoded text unreadable?

The decoded bytes may use a different character encoding or may represent a file rather than text. Try Hex output to inspect the exact bytes, or use Base64 to File to download them.

Is Base64URL the same as Base64?

It represents the same bytes but replaces + and / with - and _. Padding may be omitted when the surrounding specification permits it. Use Base64 Encode to generate the required form.