Base64 Decoder
Base64 Decoder
Decode Base64 input back to UTF-8 text with validation.
InputsManual input44 charsAuto run
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ms
Flow
- Normalize whitespace and validate Base64 syntax.
- Decode Base64 characters into byte array.
- Decode bytes as UTF-8 text with strict error handling.
Example
Worked example: decode Base64 payload
- 1 Input = RW5jb2RlIHRoaXM=
- 2 Tool validates allowed Base64 characters and padding.
- 3 Decoded output = Encode this
The Base64 text is converted back to readable UTF-8 output.
How
- Paste Base64 text into the input area.
- Run decode to convert into UTF-8 plain text.
- Review errors if Base64 syntax or UTF-8 decoding fails.
Cases
- Inspect encoded API response snippets.
- Decode copied payload segments from logs.
- Validate whether a token fragment is valid Base64.
Avoid
- Pasting Base64URL strings into standard Base64 decoder without normalization.
- Ignoring required padding when input length is not a multiple of four.
- Expecting binary file payloads to decode into readable UTF-8 text.
FAQ
Why do I get a Base64 length error?
Standard Base64 requires length to be a multiple of four after whitespace is removed.
Can this decode Base64URL strings directly?
Use the Base64URL Decoder tool for URL-safe input variants.
Does the tool validate UTF-8 output?
Yes, invalid UTF-8 byte sequences are reported as decoding errors.
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