Base62 vs Base64 // toBase62()

What Is Base62?

Base62 is a binary-to-text encoding that represents data using 62 characters: 0-9, A-Z, and a-z. Unlike Base64, it uses no special characters (no +, /, or = padding), which makes every Base62 string automatically safe to use in URLs, filenames, and database keys without any escaping.

There's no single RFC for Base62 — it's typically implemented as straight positional-numeral-system conversion, the same idea as converting a decimal number to hexadecimal, just with a 62-character alphabet instead of 16. That's different from Base64, which processes data in fixed 3-byte-to-4-character blocks.

Base62 vs Base64: Key Differences

Why Do URL Shorteners Use Base62?

Services like Bitly and TinyURL assign each link an auto-incrementing database ID, then convert that integer to Base62 to produce the short code in the URL — id 125000 becomes something like 8Q0. Because the alphabet excludes +, /, and other reserved URL characters, the result never needs percent-encoding. Base64 can't do this directly for the same reason it needs a URL-safe variant in the first place.

Try the converter above: enter an integer to see its Base62 code, or paste a Base62 code to recover the original number.

How Does Base62 Encoding Work?

Base62 encoding repeatedly divides the input number by 62, using the remainder at each step to look up a character in the alphabet, then reverses the resulting digit sequence — the same algorithm you'd use to convert a decimal number to any other base.

const ALPHABET = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';

function toBase62(n) {
  if (n === 0n) return '0';
  let out = '';
  while (n > 0n) {
    out = ALPHABET[Number(n % 62n)] + out;
    n = n / 62n;
  }
  return out;
}

function fromBase62(s) {
  let n = 0n;
  for (const ch of s) n = n * 62n + BigInt(ALPHABET.indexOf(ch));
  return n;
}

Because Base62 operates on the number as a whole rather than fixed byte blocks, encoding text requires first converting the text's bytes into one large integer (or using a per-character mapping) — it isn't a drop-in replacement for encoding arbitrary binary files the way Base64 file encoding is.

When Should You Use Base62 Instead of Base64?

Choose Base62 when you're encoding a number (a database ID, counter, or hash-derived integer) into a short, URL-safe, human-typeable string — short links, invite codes, order references, or shard/partition keys. Choose Base64 when you're encoding arbitrary binary data (images, files, JSON payloads) that needs a lossless, standardized, reversible text representation. The two aren't really interchangeable: Base62 shines at compressing small integers into short strings, while Base64 is built for streaming raw bytes through text-only channels.

Frequently Asked Questions