Nano ID is a tiny, URL-safe unique-ID format. By default it is 21 characters from a 64-symbol alphabet, giving collision odds comparable to a UUID v4 in a more compact, copy-friendly string.

How does the random selection avoid bias?

This generator uses rejection sampling over the alphabet — the same approach as the reference nanoid library — so every character is equally likely with no modulo bias, drawn from the browser's Web Crypto random source.

How is Nano ID different from a UUID?

A UUID v4 is 36 characters with hyphens and a fixed hex-based format. A default Nano ID is 21 characters from a 64-symbol URL-safe alphabet, so it is shorter and has no special characters, while keeping comparable collision resistance.

What characters are in the default alphabet?

The default 64-symbol alphabet is A-Z, a-z, 0-9 plus the underscore and hyphen — all URL-safe, so IDs can be dropped straight into URLs, filenames or database keys without encoding.

How long should my Nano ID be?

21 characters is the standard length and is safe for almost all applications. Longer IDs reduce collision probability further; shorter IDs save space but increase collision odds, so test the collision math against your expected number of IDs before going below 12.

Can I use my own custom alphabet?

Yes. Paste any set of at least two characters into the Alphabet field — for example only lowercase letters and digits to avoid ambiguous characters. If you enter fewer than two characters the default URL-safe alphabet is used.

How many IDs can I generate at once?

You can generate between 1 and 1000 IDs in a single batch, and copy them all together with one click.

Is anything uploaded when I generate IDs?

No. The random bytes and the IDs are produced entirely in your browser, and nothing is uploaded — your custom alphabet never leaves your device.

Nano ID Generator — Gera Tools

Nano ID is a tiny, URL-safe unique-ID format used widely as a shorter alternative to UUIDs for database keys, short links, filenames and API tokens. This generator creates Nano IDs entirely in your browser with a length, count and alphabet you control.

How it works

Each character is chosen from your alphabet using rejection sampling, the same unbiased technique as the reference nanoid library. The generator computes the smallest bitmask that covers the alphabet length, then draws cryptographically random bytes from the browser’s Web Crypto source (crypto.getRandomValues). Each byte is masked, and any value that falls outside the alphabet range is discarded and re-drawn. This guarantees no modulo bias — every character is equally likely.

The default alphabet has 64 symbols (A-Z a-z 0-9 _ -), all URL-safe, and the default length is 21 characters, giving collision resistance comparable to a UUID v4.

Example

With the default settings, a generated ID looks like this:

Setting	Value
Length	21
Alphabet size	64
Example output	`V1StGXR8_Z5jdHi6B-myT`

Shrink the length to 10 and restrict the alphabet to 0123456789abcdef and you get a short hex-style ID such as a3f90c1b7e. Set the count to 100 to mint a whole batch and copy them all at once.

Everything runs entirely in your browser — the random bytes, your custom alphabet and the generated IDs never leave your device.