Nano ID for C

A tiny, secure, URL-friendly unique string ID generator for C.

• Small. 199 bytes. Header-only. No dependencies other than libc.
• Safe. Uses getentropy(3), a modern, reliable, secure randomness source.
• Short IDs. A default Nano ID is 15 characters shorter than a UUIDv4 while encoding 4 bits more entropy.
• Portable. POSIX-compliant. Available in 29 programming languages.

#include <nanoid.h>
#include <stdio.h>
#include <stdlib.h>

int main() {
  char id[NANOIDLEN + 1] = "";

  if (nanoidgen(id, NANOIDLEN))
    return EXIT_FAILURE;

  puts(id);
}

$ cc main.c -o example
$ ./example
V1StGXR8_Z5jdHi6B-myT

Overview

Nano IDs are unique string IDs where each character is an alphanumeric, a hyphen, or an underscore. Think of them as random unpadded Base64url strings. You've already seen this format elsewhere: on YouTube!

A default Nano ID is 21 characters long, encoding 126 bits of entropy at 6 bits per character.

nanoid.h is a self-contained Nano ID generator built on top of the getentropy(3) randomness source. It's as portable as getentropy(3) itself, which is a part of the POSIX.1-2024 standard. Just grab the header and use it wherever you wish!

Usage

Works out of the box on NetBSD, OpenBSD, Linux, Android, macOS, illumos, Solaris, FreeBSD, DragonFly, Haiku, GNU Hurd, Fuchsia, Emscripten, and WASI. Windows support requires a getentropy(3) shim.

To include nanoid(3) copy nanoid.h and LICENSE.txt to your project.

To build nanoidgen(1) run make nanoidgen.

To build and install the project use Meson:

meson setup ../nanoid && \
  ninja -C ../nanoid && \
  sudo ninja -C ../nanoid install

Documentation

See the PDF manual at https://lukateras.github.io/nanoid.h/man.pdf.

nanoid(3)

#include <nanoid.h>

• macro NANOIDLEN

  The default Nano ID length of 21.

• static inline function int *nanoidgen(char *buffer, size_t length)

  Fills the buffer with a Nano ID of the specified length up to GETENTROPY_MAX (256).

  Returns the return value of getentropy(3).

nanoidgen(1)

$ nanoidgen [length]

Generates a Nano ID of the default length (21), or the specified length within 1 and GETENTROPY_MAX (256), and prints it to the standard output.

Attribution

Port of Nano ID by Andrey Sitnik.

Original logo by Anton Lovchikov.

Social preview background texture by Tuomo.

Social preview logo assistance by Tanya Nevskaya.