Base64 is not encryption
It turns bytes into 64 printable characters so they survive channels that only carry text. Anyone can reverse it in a second. Never use it to hide anything.
Why it grows by a third
Every three bytes become four characters, so encoded data is about 33% larger than the original. That is the cost of squeezing arbitrary bytes through a text-only pipe.
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Frequently asked questions
Q. Does it handle non-Latin text?
Yes. The text is converted to UTF-8 bytes first, so Japanese, Arabic, emoji and anything else round-trip correctly.
Q. What is URL-safe Base64?
A variant that uses - and _ instead of + and /, so the result can sit in a URL without escaping. JWTs use it. This tool handles the standard alphabet.
Q. Why does decoding fail?
Usually a truncated string or one that picked up whitespace or a stray character. Base64 length must be a multiple of four, padded with = if needed.