Base64 to Binary Converter // toString(2)

What Is Base64 to Binary Conversion?

Base64 to binary conversion decodes a Base64 string into its raw bit pattern — the sequence of 1s and 0s that make up the underlying bytes — rather than into readable text or an image. It's mainly used for learning how the encoding works, debugging byte-level issues, or comparing output against a spec. This is a different tool from the Base64 file decoder, which reconstructs a downloadable file instead of showing the bit pattern.

For the conceptual comparison between the two encodings — size overhead, character sets, when to use which — see Base64 vs Binary.

How Does the Conversion Work?

Base64 → Binary: the tool decodes the Base64 string to raw bytes with atob(), then converts each byte to an 8-bit binary string with leading zeros preserved, space-separated for readability.

Binary → Base64: the tool reads the input as space- or line-separated 8-bit groups, converts each group back to a byte, and re-encodes the byte sequence with btoa().

// Base64 -> binary
const bytes = atob(b64Str);
const bits = [...bytes].map(c => c.charCodeAt(0).toString(2).padStart(8, '0')).join(' ');

// Binary -> Base64
const bytes2 = bits.split(/\s+/).map(b => String.fromCharCode(parseInt(b, 2))).join('');
const b64 = btoa(bytes2);

Example

Is This Converter Private?

Yes. All conversion runs locally using atob()/btoa() and basic string operations — nothing is uploaded to a server.

Frequently Asked Questions