Base64 Encoder/Decoder

Convert text to and from Base64 using a UTF-8 safe implementation built on top of the browser's native btoa/atob routines. Encoding wraps each non-ASCII character as percent-encoded UTF-8 bytes before base64 conversion, so multilingual text (CJK, emoji, accented letters) survives a full encode-decode round trip.

1. Toggle the Encode or Decode mode tab at the top.\n2. Paste plain text (encode) or a Base64 string (decode) into the input area.\n3. Click the Encode / Decode button to run the conversion.\n4. Copy the result with the Copy button in the output card. An error is shown if the decoded input is not valid Base64.

Output uses standard Base64 with + and / characters plus = padding, not the URL-safe variant. Decode rejects malformed input and surfaces a localized "invalid Base64" error. Switching modes clears the output. All work runs locally in the browser via btoa/atob — no network calls, no length cap beyond available memory.