Does it handle URL-safe Base64?

Yes. The decoder accepts both the standard + / alphabet and the URL-safe - _ alphabet, and adds any missing padding automatically.

Why do I get an invalid input error?

The string contains characters that are not valid Base64, or its length is malformed. Check for stray spaces or truncation. Invalid UTF-8 byte sequences are also flagged.

No. Decoding runs entirely in your browser with built-in APIs — nothing is transmitted anywhere.

Base64 Decoder

Decode Base64 back to text — standard and URL-safe — in your browser.

Base64 decoder

Turn a Base64 string back into readable text. The decoder accepts both standard and URL-safe Base64, fixes missing padding for you, and decodes the bytes as UTF-8 — all in your browser, with nothing uploaded.

To encode in the first place, use the Base64 encoder.