Convert text to Base64, or decode a Base64 string back to text.
Base64 encodes every 3 bytes of input as 4 output characters, so encoded text is roughly 33% larger than the original — this is shown as a positive "Size change" percentage in the result.
Yes — this tool is UTF-8 safe, so emoji, Urdu, or other non-ASCII text is converted to its UTF-8 byte sequence before Base64 encoding, and decoded back the same way, avoiding the mangled output that a naive btoa/atob can produce.
The decoder expects a valid Base64 string (only A–Z, a–z, 0–9, +, /, and = padding). If the text contains other characters or isn't properly padded, it isn't valid Base64 and the calculator shows an error instead of garbled output.