Base64 Encode/Decode

Paste plain text, get Base64. Paste Base64, get plain text back. The tool auto-detects which direction you probably want, but you can force it either way. Handles UTF-8 properly, so emojis, accented characters, and CJK text won't turn into garbage on the other end.

Common use cases

Decoding data URIs. Those data:image/png;base64,... strings in CSS and HTML. Paste the encoded part, see what's in it.

Working with auth headers. HTTP Basic auth base64-encodes your username and password. Encoding is not encryption, a distinction that matters. This tool lets you encode credentials for testing or decode them when debugging.

Handling API payloads. Plenty of APIs return binary data as Base64 strings in JSON responses because JSON has no native binary type. JWTs are Base64url-encoded in each of their three segments.

Things to know

The UTF-8 handling is where most Base64 tools quietly break. The browser's built-in btoa() only handles Latin-1 characters. Throw an emoji at it and it throws an error. This tool runs text through TextEncoder first to get proper UTF-8 bytes, then encodes those. On decode, it reverses the process with TextDecoder. You can round-trip any Unicode character without losing anything.

Every 3 bytes of input become 4 characters of output, so Base64 data is about 33% larger than the original. That's the tradeoff: safe to embed anywhere, costs you some size.

Privacy

Runs entirely in your browser. No server, no logs, no upload. Your API tokens, auth headers, and mysterious encoded config values stay on your machine.