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.

What is the Base36 Encoder and Decoder?

Convert whole numbers to base-36 using the digits 0-9 and letters a-z, or decode a base-36 string back to a decimal integer. Case-insensitive decoding and arbitrary-precision math handle very large IDs exactly. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Base36 Encoder and Decoder

Name: Base36 Encoder and Decoder
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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.

When developers actually use base-36

Base-36 fills a specific niche: you need an integer to be human-readable, typeable, and compact, but you do not need it to be case-sensitive. A few common applications:

Short URL identifiers. A sequential database row ID like 987654321 encodes to gly57 in base-36 — five characters instead of nine, using only letters and digits. The case-insensitivity is a useful property here: users who type a URL by hand from memory can use any mixture of upper and lower case and still reach the right resource.

Invite codes and vouchers. Systems that generate one-time codes for referrals, discounts, or beta invites often use base-36 because the output is safe to read aloud over a phone call or read from a printed page without ambiguity about which character is which.

Order and invoice references. A business that assigns sequential order numbers can encode them as short base-36 strings for display on receipts (for example order 4f2a) while keeping the underlying integer as the primary key in the database.

Comparing base-36 to neighbouring encodings

Encoding	Symbols	Case sensitive?	Characters needed for 2^32
Decimal (base-10)	0–9	No	10
Hexadecimal (base-16)	0–9, a–f	No (by convention)	8
Base-36	0–9, a–z	No	7
Base-62	0–9, a–z, A–Z	Yes	6
Base-64	0–9, a–z, A–Z, +, /	Yes + special chars	6

Base-36 saves one character compared to hex and two compared to decimal, at no cost in readability — and it avoids the case-sensitivity requirement of base-62. If you are operating in an environment where upper and lower case are equivalent (a domain name, a case-insensitive filesystem path, a voice system), base-36 is often the right choice over base-62.

Large numbers and precision

The tool uses arbitrary-precision arithmetic. This matters for modern systems: database primary keys generated by distributed ID schemes (such as Snowflake IDs) are often 64-bit integers too large to represent exactly as a JavaScript number. Encoding and decoding via BigInt keeps the conversion exact to the last digit, which is important if the encoded value is also used as a database key.