What characters does base-36 use?

Base-36 uses the ten digits 0 to 9 followed by the twenty-six letters a to z, for 36 symbols in total. Each position is therefore worth 36 times the one to its right, the same way base-10 positions are worth 10 times the next.

Why encode numbers in base-36?

Base-36 is the most compact representation that stays case-insensitive and URL-safe using only letters and digits. It is popular for short identifiers, invoice numbers, and shortened URLs because a large number fits in far fewer characters than decimal.

Does this encode text or only numbers?

It encodes whole numbers, not arbitrary text. Base-36 represents an integer in a different radix, so the input must be a non-negative whole number. To encode text bytes safely, use Base32 or Base64 instead.

Is decoding case-sensitive?

No. Decoding treats uppercase and lowercase letters the same, so HELLO and hello decode to the same number. Encoding always outputs lowercase letters for consistency.

Can it handle numbers larger than a normal integer?

Yes. The tool uses arbitrary-precision arithmetic, so numbers far beyond the usual 64-bit range convert exactly with no rounding. This matters for large database IDs and cryptographic values.

Base36 Encoder and Decoder

Base36 represents whole numbers using all ten digits and all twenty-six letters, giving a compact, case-insensitive, alphanumeric form. It is the encoding behind many short IDs and shortened-URL schemes, where fitting a big number into a few readable characters is the goal.

How it works

Encoding repeatedly divides the number by 36 and reads the remainders from last to first; decoding does the reverse with a positional sum:

digits = 0123456789abcdefghijklmnopqrstuvwxyz

encode:  while n > 0 { prepend digits[n mod 36]; n = n div 36 }
decode:  value = 0; for each char c { value = value*36 + index(c) }

All arithmetic is done with arbitrary-precision integers, so the conversion is exact even for numbers with hundreds of digits.

Example and tips

The decimal number 123456789 becomes 21i3v9 in base-36 — six characters instead of nine. Decoding 21i3v9 returns 123456789, and decoding 21I3V9 gives the same result because letters are case-insensitive. Use base-36 when you want short human-friendly identifiers; if you need to encode raw bytes or text rather than an integer, reach for Base32 or Base64 instead.