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Decode Base58 encoded text (Bitcoin alphabet)
Decode Base58 encoded strings instantly with our free online Base58 decoder tool. This decoder helps cryptocurrency developers and blockchain professionals convert Base58-encoded data back into readable text using the Bitcoin alphabet. Simply paste your Base58 string and get the decoded output in real-time.
Base58 decoder converts Base58-encoded strings back to original bytes. Essential for processing cryptocurrency addresses, IPFS hashes, and other Base58-encoded identifiers. Must handle leading '1' characters and optional checksums.
Each character maps to a value 0-57. Decoder treats the string as a base-58 number, converts to a big integer, then to bytes. Leading '1' characters become leading zero bytes (important for address prefixes).
Reverse mapping from 58 characters to values. For Base58Check, verify last 4 bytes match double-SHA256 checksum of preceding bytes. Invalid characters or failed checksum should reject the input entirely.
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const BASE58_CHARS = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz';
function base58Decode(str) {
// Count leading '1's (represent leading zero bytes)
let zeros = 0;
for (const c of str) {
if (c === '1') zeros++;
else break;
}
// Convert from base58 to big integer
let num = BigInt(0);
for (const char of str) {
const val = BASE58_CHARS.indexOf(char);
if (val === -1) throw new Error('Invalid Base58 character');
num = num * 58n + BigInt(val);
}
// Convert to bytes
const bytes = [];
while (num > 0n) {
bytes.unshift(Number(num % 256n));
num = num / 256n;
}
// Add leading zeros
return new Uint8Array([...Array(zeros).fill(0), ...bytes]);
}
base58Decode('9Ajdvzr'); // Uint8Array [72, 101, 108, 108, 111] ("Hello")Count leading "1"s, convert base-58 to integer, extract bytes, prepend zeros.
Use Base58 decoder for cryptocurrency address validation, IPFS hash processing, and decoding any Base58-encoded identifier. Always validate checksums for financial data.
Decode Base58Check, verify 4-byte checksum matches double-SHA256 of payload. Check version byte for expected address type. Invalid checksum means typo or corruption.