Base64

Base64 is a standard encoding scheme that represents binary data using 64 printable characters: uppercase and lowercase letters, digits, plus, and slash. Every 3 bytes of data become 4 characters, allowing arbitrary files or cryptographic material to travel safely through systems designed for plain text.

Why it matters

Base64 predates bitcoin by decades and runs quietly through email attachments, web pages, and APIs everywhere. In bitcoin it appears wherever structured binary data must be copied between programs by hand: partially signed bitcoin transactions defined in BIP 174 are conventionally exchanged as Base64 strings, and signed messages proving address ownership use it as well. When a hardware wallet workflow asks a user to paste a long block of letters and symbols, it is usually Base64 underneath.

How it works

The encoder reads binary input 6 bits at a time, and each 6-bit value, a number from 0 to 63, selects one character from the alphabet. Because 6 does not divide evenly into 8, output is padded with equals signs to a multiple of 4 characters, and encoded data is about 33 percent larger than the original. Unlike bitcoin's Base58, Base64 includes no checksum and keeps visually similar characters, so it is meant for machine-to-machine transfer rather than human transcription. The two encodings answer different questions: Base64 asks how to move bytes through text systems efficiently, Base58 asks how to let a human copy money instructions without catastrophe.