Base64 Encoder & Decoder
Edit either side and the other follows. Encoding and decoding run entirely in your browser, so nothing you type ever leaves this page.
How it works
仕組みConvert text to Base64 and back, live in both directions: edit the plain side and the encoded side updates, paste Base64 and the plain side decodes. It all happens in your browser, so secrets and tokens never leave your machine. The tool is UTF-8 safe, meaning Japanese, emoji, and accented characters round-trip correctly where naive converters mangle them. A toggle switches to the URL-safe variant (- and _ instead of + and /, padding stripped) used in JWTs and query strings, and plates show plain byte count, Base64 length, and the size overhead, typically about +33%.
No. It’s only an encoding, a way to represent arbitrary bytes using 64 safe printable characters. Anyone can decode it instantly, as this page proves. Use it to transport data through text-only channels (JSON, URLs, email), never to hide or protect it.
Base64 packs 3 bytes of input into 4 output characters, so the size grows by roughly 33%, plus up to two = padding characters. That’s the price of using only safe printable characters. The overhead plate shows the exact figure for your input; multi-byte characters like kanji cost 3 plain bytes each, so Japanese text grows more than its character count suggests.
Standard Base64 uses + and /, which have special meanings inside URLs, so the URL-safe alphabet swaps them for - and _ and usually drops the = padding. JWTs, OAuth parameters, and many APIs use this form. The decoder here accepts both variants automatically and re-pads for you, so you can paste either.