Base64 Encode / Decode

How it works

1. Choose Encode to turn plain text into Base64, or Decode to turn a Base64 string back into text.
2. Paste the input. For decoding, both the standard alphabet with + and / and the URL-safe one with - and _ are accepted; missing padding is tolerated.
3. Turn on URL-safe if the result will go into a URL, a JWT or a filename, so no characters need percent-encoding.
4. Press Convert and copy the result. Accented characters, CJK text and emoji are encoded as UTF-8 bytes, matching what btoa-based encoders often get wrong.

Frequently asked questions

Is Base64 encryption?

No. Base64 is a reversible encoding that represents bytes using 64 printable characters. Anyone can decode it instantly. Use it for transport and embedding, never for hiding secrets.

How does the tool handle non-ASCII text like accents, Japanese or emoji?

The text is converted to UTF-8 bytes before encoding, and decoded output is interpreted as UTF-8. This matches what most languages and HTTP libraries do. Plain JavaScript btoa() only accepts Latin-1, which is why naive encoders throw on such characters.

What is the difference between standard and URL-safe Base64?

Standard Base64 (RFC 4648 section 4) uses + and / plus = padding. URL-safe Base64 (section 5) replaces them with - and _ and usually drops the padding, so the string can be used in URLs, cookies and JWTs without escaping. The decoder here accepts both.

Why is the encoded output about a third longer than my text?

Base64 packs 3 bytes into 4 characters, so output size is roughly 4/3 of the input plus up to 2 padding characters. That overhead is the price of using only printable characters.

Is my data sent to a server?

No. Encoding and decoding run entirely in the browser. You can convert API keys, connection strings or personal text without anything leaving your device.