Base64 Encoder and Decoder

Base64 turns any text into a string made only of the 64 safe characters A-Z, a-z, 0-9, plus, slash, and equals for padding. It is handy when a system only accepts plain ASCII, for example when embedding data in URLs, JSON, or email headers.

Choose the Encode mode above, paste or type your text, and the Base64 appears instantly in the output box. Click Copy result to put it on your clipboard.

Switch to the Decode mode, paste the Base64 string, and the original text appears below. If the string is not valid Base64 you will see a clear message explaining what to check.

Standard Base64 uses plus and slash, which have special meanings in URLs. The URL-safe variant swaps them for hyphen and underscore and drops the padding. Turn it on when the output is going into a link, a filename, or a token.

Many quick tools call the browser btoa function directly on the text, and btoa only understands single-byte characters. Emoji, Chinese characters, and accented letters get mangled. This tool first converts your text to UTF-8 bytes with TextEncoder, so every character survives the round trip.

The string probably contains a typo or a character outside the Base64 alphabet. This tool ignores line breaks, which are common in pasted output, but anything else outside A-Z, a-z, 0-9, plus, slash, and equals is rejected with an explanation.

This tool is deliberately text-only. Encoding a large file in the browser can use several times the file size in memory and freeze the page, so file conversion is out of scope. For files, use a desktop tool or a short script instead.

No. Everything happens in your browser with JavaScript only. Nothing you type is sent to a server, stored, or logged.