Base58 Decoder: Base58 to Hex and Text

How to decode Base58

1. Paste the string into Input · Base58. Spaces and line breaks are ignored.
2. Read the bytes in Output · Hex. Under the output you can switch Case, add a Separator such as a space or :, or break the dump into 16 or 32 Bytes per line.
3. If the string is not Bitcoin-style Base58, change Alphabet under the input to Flickr or Ripple.
4. For other views, change To: Text if the data was a string, Base64 for an API or config file. Base58 to Base64 is a page set up for that conversion.
5. Copy output, Download the hex, or Save bytes to get the decoded bytes as a file.

What common Base58 strings decode to

Reading the bytes tells you the structure. A 25-byte result starting with 00 or 05 is a Bitcoin address with its checksum still attached, a 34-byte result starting with 1220 is a CIDv0, and 32 bytes with no visible structure is most likely a public key.

Leading 1s are zero bytes

In Base58 every leading 1 decodes to one 00 byte, and the rest of the string decodes as a single number. This decoder keeps those bytes, so the genesis address above returns 25 bytes, not 24. A decoder that converts only the number loses them, and the first sign is usually a key that is one byte short or a checksum that never matches.

The rule runs the other way too: 1111 is four zero bytes, while 2 is the single byte 01.

When decoding fails

• Unexpected character "0", "O", "I" or "l". These four are not in the Base58 alphabet, which leaves them out because they look like other characters. The error gives the position; it is usually a transcription mistake.
• Unexpected +, / or =. The string is Base64. Use the Base64 decoder.
• The input starts with bc1. That is a Bech32 SegWit address, a different encoding with its own checksum and alphabet. It either fails here or decodes to meaningless bytes.
• The hex is right but too long by 4 bytes. You decoded a Base58Check value as plain Base58. The last 4 bytes are the checksum; drop them or use Base58Check.
• Input over 64 KB. Base58 treats the whole input as one number, so the tool stops at 64 KB to stay responsive. Real Base58 values are a few dozen characters.

Decode Base58 to hex in JavaScript

BigInt makes the conversion short. This works in browsers and in Node.js:

const ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";

function base58ToHex(s) {
  let n = 0n;
  for (const ch of s) {
    const v = ALPHABET.indexOf(ch);
    if (v < 0) throw new Error(`not Base58: ${ch}`);
    n = n * 58n + BigInt(v);
  }
  let hex = n === 0n ? "" : n.toString(16);
  if (hex.length % 2) hex = "0" + hex;
  const zeros = s.length - s.replace(/^1+/, "").length;
  return "00".repeat(zeros) + hex;
}

base58ToHex("1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa");
// '0062e907b15cbf27d5425399ebf6f0fb50ebb88f18c29b7d93'

For more byte handling in JavaScript, see the JavaScript page.

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