Module nanoid 

Available on crate feature nanoid only.

NanoID generation

URL-safe random strings of configurable length over a configurable alphabet. The default alphabet is the 64-character URL-safe set (A-Z, a-z, 0-9, _, -) and the default length is 21 — the same defaults as the original JavaScript reference, giving roughly 1 trillion years to a 1 % collision probability at 1000 IDs/second.

use id_forge::nanoid;

let id = nanoid::generate();
assert_eq!(id.len(), 21);

let short = nanoid::with_length(8);
assert_eq!(short.len(), 8);

let hex = nanoid::custom(16, b"0123456789abcdef");
assert_eq!(hex.len(), 16);
assert!(hex.chars().all(|c| "0123456789abcdef".contains(c)));

Bias-free selection

NanoID picks each character by drawing bits from the shared xoshiro256** generator, masking to the smallest power of two that covers the alphabet, and rejecting indices that fall above the alphabet’s size. For a 64-character alphabet the acceptance rate is 100 %; for a 17-character alphabet it’s 17/32 = 53 %. Either way, every character of the alphabet has identical probability of being chosen.

The 0.1.0 placeholder used a linear congruential generator with byte % alphabet.len(), which biased the result whenever the alphabet size was not a power of two. 0.9.3 fixes that.

Randomness quality

The bit source is the same fast non-cryptographic generator used by uuid and ulid. NanoIDs from this crate are suitable for collision-resistant identifiers, not session tokens.

Enums

AlphabetError

Error returned by try_custom and validate_alphabet.

Constants

DEFAULT_ALPHABET

Default alphabet: URL-safe, 64 characters (_- + alphanumeric).

DEFAULT_LENGTH

Default length: 21 characters.

Functions

custom

Generate a NanoID with a custom length and alphabet.

generate

Generate a NanoID using the default alphabet and length.

try_custom

Strict counterpart to custom: validates the alphabet first.

validate_alphabet

Verify that an alphabet is non-empty and free of duplicate bytes.

with_length

Generate a NanoID of the given length using the default alphabet.