Base64 Decoder
Decode Base64 encoded strings back to plain text
Input Information
Result
Base64 Decoder converts Base64 encoded strings back to their original plain text. This is useful for decoding API responses, JWT tokens, email content, and other Base64-encoded data.
The decoder handles Unicode/UTF-8 text properly, returning the exact original text that was encoded.
Term Glossary
- Base64
- An encoding scheme that represents binary data using 64 ASCII characters. Decoding restores the original text or binary data.
- 6-bit Encoding
- In Base64 each character represents 6 bits of the original data. Four characters (4×6 bits) represent the original 3 bytes (24 bits).
- 1
Paste the Base64 string
Paste the Base64 string (A-Z, a-z, 0-9, +, /, =) into the input.
- 2
Click decode
Clicking the button converts the Base64 back to bytes and displays them as text.
- 3
Choose a charset
If the text is garbled, select a charset other than UTF-8 to recover the correct original.
- 4
View the decoded text
Verify the decoded original and copy it if needed.
Example 1 — Basic string
aGVsbG8= → "hello"
The 5-byte string 'hello' encodes to aGVsbG8=. The trailing = is padding to complete the 3-byte grouping.
Example 2 — Two words
SGVsbG8gV29ybGQ= → "Hello World"
'Hello World' is 11 bytes including the space, encoding to SGVsbG8gV29ybGQ=. Case and the space are preserved exactly.
Example 3 — UTF-8 text
7ZWY6rWt → "한글"
Korean text is first converted to UTF-8 bytes, then encoded to Base64. Decoding interprets those bytes as UTF-8 to restore the original Korean.
Decoding Process:
- Step 1: Validate the input contains only valid Base64 characters (A-Z, a-z, 0-9, +, /, =).
- Step 2: Convert each Base64 character back to its 6-bit value.
- Step 3: Reassemble the 6-bit groups into 8-bit bytes.
- Step 4: Convert the byte array back to the original text encoding.
"SGVsbG8=" → "Hello"
Tips:
- Valid Base64 strings have a length that is a multiple of 4 (after padding with =).
- If you get garbled output, the original text might have been in a different encoding.
- Common sources of Base64 data: JWT headers, email attachments, HTTP Basic Auth headers.
- The output preserves the original text including any special characters and line breaks.
QWhat is Base64?
Base64 is an encoding scheme that represents binary data using 64 ASCII characters (A-Z, a-z, 0-9, +, /). It lets binary data travel safely over text-only channels like email, JSON, and URLs.
QWhy is the decoded text garbled?
The decoded output appears garbled when the source was binary data (images, files) rather than text, or when the bytes are not valid UTF-8. For text, the bytes may be from a different charset — try another charset.
QWhat is the difference between URL-safe and standard Base64?
Standard Base64 uses + and /, which have special meaning in URLs. URL-safe Base64 replaces + with - and / with _, and omits the trailing = padding so it fits safely in a URL — JWT tokens are a common example.
QWhy is there padding (=) at the end?
Base64 encodes 3 bytes as 4 characters, so when the data length is not a multiple of 3 the final group is incomplete. The = character pads the output to a multiple of 4. This padding is ignored during decoding.
QCan I decode binary data?
Technically yes, but binary data shown as text produces unreadable characters. Binary Base64 (images, files) should be decoded with a dedicated tool and saved to a file. This tool is optimized for decoding text (UTF-8).