Base64 encoder and decoder

No. Base64 is an encoding, not a cipher — anyone can decode it in seconds. It exists to carry binary data safely through text-only channels such as email or JSON, not to keep anything secret.

The browser’s built-in btoa() only accepts characters below U+0100, so many tools mangle anything else. This tool encodes to UTF-8 bytes first, which round-trips any character correctly.

A variant that replaces + with - and / with _ so the result can sit in a URL or filename without escaping. It is the encoding used by JSON Web Tokens.

Because the decoded bytes are not valid UTF-8, which usually means the string is an image, a zip or an encrypted blob rather than text. Showing it as text would replace every unreadable byte with a question-mark character and hand you corrupted data, so the tool says so and offers the exact bytes as a download instead.

Yes, and that is the most common reason two tools disagree. A newline is a byte like any other, so it is encoded. This tool encodes exactly what you paste, warns you when the input starts or ends with whitespace, and lets you trim it deliberately.

One mebibyte per conversion. The work happens in your browser tab, and a much larger paste would make the page stall on a modest laptop or phone, so the limit is enforced with a clear message rather than a frozen page.