Base64 Encode / Decode

The Base64 encoder and decoder converts text into Base64 and back. Base64 is the standard way to represent binary-safe data as plain ASCII text — every email attachment, data URL, JWT token, anddata: URI you meet online is built on it. This tool does both directions instantly, with correct UTF-8 handling so Chinese, emoji, and other multi-byte characters survive the round trip.

Type or paste text in the input, choose encode or decode, and the output updates as you type. Everything runs in your browser — nothing is uploaded, logged, or stored.

What Base64 actually is

Base64 takes every 3 bytes of input and rewrites them as 4 printable characters from a 62-character alphabet (A–Z, a–z, 0–9, plus + and /, with = as padding). The result is about 33% larger than the original, but it contains only characters that survive any transport channel that might mangle binary data — email systems, URLs, XML, plain-text protocols.

That is the core trade: Base64 makes data portable at the cost of size. You use it when a channel cannot carry raw bytes — embedding a small image directly in CSS, putting a file into a JSON field, passing binary through an environment variable, or constructing the middle section of a JWT.

Why UTF-8 handling matters

The classic pitfall: JavaScript's built-in btoa() function only handles Latin-1 characters. Pass it Chinese text or an emoji and it throws an error — or worse, in naive implementations, silently corrupts the string. This tool encodes with UTF-8 first, then applies Base64, so Hello, 世界! 👋 encodes and decodes back to exactly the same text. If you have ever seen a "character out of range" error from a quick one-liner, this is the problem it causes.

The same care applies in reverse: decoding produces UTF-8 bytes and decodes them as text, so multi-byte characters come back intact rather than as mojibake.

Error reporting

Decoding invalid input fails loudly. The tool checks the character alphabet and the length (Base64 must be a multiple of 4 characters after whitespace is stripped) before decoding, and reports a clear message instead of returning garbled output. Whitespace and line breaks inside the input are ignored, because real-world Base64 — PEM blocks, MIME bodies, wrapped API responses — is routinely line-wrapped.

Common uses

Developers encode a short string to build a Basic-auth header, decode a JWT payload to inspect its claims, or embed an SVG as a data URL. Engineers verify checksums and tokens by round-tripping them through the tool. Analysts decode Base64 fields found in logs or API responses. The reverse direction — decoding — is just as common, since much of Base64 you encounter in the wild was produced somewhere else.

Encoding is not encryption

The most important caveat: Base64 is an encoding, not a security measure. Anyone can decode it in one line, so never treat a Base64-encoded password, API key, or token as hidden. It protects data integrity across text-only channels — nothing more. If you need actual confidentiality, use proper encryption.