Which characters does Bitcoin Base58 leave out, and why?

It omits four characters that are easy to confuse when read or transcribed by hand: the digit zero, the capital letter O, the capital letter I, and the lowercase letter L. Removing them prevents costly typos when someone copies an address or key by eye.

How is Base58 different from Base64?

Base64 packs bits in fixed groups and is fast, but it includes plus, slash, and equals which are awkward in URLs and prone to look-alike errors. Base58 instead treats the whole input as one big number and converts it to base 58, trading speed for a human-friendly, delimiter-free alphabet.

Why do leading zero bytes become leading ones?

Big-integer base conversion naturally drops leading zeros, so Base58 encodes each leading zero byte as a single '1' (the first symbol of the alphabet). The decoder reverses this, restoring one zero byte for every leading '1'. This is how Bitcoin addresses keep their version-byte prefix.

Does this tool add a checksum like a real Bitcoin address?

No. This is raw Base58, not Base58Check. A full Bitcoin address also appends a 4-byte double-SHA-256 checksum before encoding. For checksum-protected encoding, use the Base58 Ripple tool's Base58Check mode as a reference, or treat this tool as the underlying encoder.

Is anything sent to a server?

No. Encoding and decoding happen entirely in your browser, so you can safely process keys, hashes, and other sensitive values without them leaving your device.

Base58 Bitcoin Encoder/Decoder

Base58 is a binary-to-text encoding introduced by Bitcoin to represent addresses and keys in a form that humans can copy without errors. It uses 58 symbols, deliberately dropping the four characters that look alike in many fonts. This tool encodes UTF-8 text to Bitcoin Base58 and decodes it back, entirely in your browser.

How it works

Unlike Base64, Base58 does not work on fixed bit groups. It treats the entire input as one large integer and repeatedly divides by 58:

The input bytes are interpreted as a big-endian number.
That number is divided by 58 over and over; each remainder selects one symbol from the alphabet 123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz.
The symbols come out least-significant first, so they are reversed for the final string.
Each leading zero byte in the input is encoded separately as a leading 1, because the numeric conversion alone would lose it.

Decoding runs the same process in reverse: characters are accumulated into a big integer, the integer is rendered back into bytes, and each leading 1 is restored as a zero byte.

Tips and example

Encoding the text Hello World! produces 2NEpo7TZRRrLZSi2U. Because Base58 omits 0, O, I, and l, a string that contains any of those characters is invalid and the decoder will reject it with the offending character named. Remember that a real Bitcoin address is Base58Check — it carries an extra four-byte checksum — so a bare Base58 string from this tool is the building block, not a complete address.