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.

What is the Nano ID Generator?

Free Nano ID generator — create short, URL-safe, cryptographically random IDs with a custom length and alphabet. Runs entirely in your browser, nothing is uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

Nano ID Generator — Gera Tools

Name: Nano ID Generator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Get one useful tool a week

Like this tool? Enter your email and we'll send you one genuinely useful Gera tool a week — plus a link to come back to this one. No spam, one-click unsubscribe any time.

Nano ID is a compact, URL-safe unique-ID format that is widely used as a shorter alternative to UUIDs for database primary keys, short links, session tokens, filenames, and API identifiers. This generator produces Nano IDs entirely in your browser with the length, count, and alphabet you specify.

How it works

Each character is chosen from your alphabet using rejection sampling — the same unbiased technique used by the reference nanoid JavaScript library. The generator computes the smallest power-of-two bitmask that covers the alphabet size, draws cryptographically random bytes from crypto.getRandomValues, masks each byte, and discards any value that falls outside the valid alphabet range before re-drawing. This eliminates modulo bias — a common flaw in naive implementations where characters near the beginning of the alphabet appear slightly more often than others.

The default alphabet is the 64-symbol URL-safe set (A–Z, a–z, 0–9, _, -), and the default length is 21 characters, producing collision resistance comparable to a UUID v4 in roughly 60% fewer characters.

Nano ID vs. UUID v4

	UUID v4	Nano ID (default)
Length	36 characters	21 characters
Character set	hex + hyphens	64 URL-safe chars
URL-safe	No (hyphens OK, but verbose)	Yes, no encoding needed
Collision resistance	~2¹²²	~2¹²⁶
Randomness source	Depends on implementation	Web Crypto API

Nano IDs are shorter and drop straight into URLs, filenames, and database keys without percent-encoding. UUIDs have the advantage of being universally recognisable and parseable by existing tooling that specifically expects the UUID format.

Customising the alphabet

Hex-style IDs: set the alphabet to 0123456789abcdef and length to 16 for compact hex identifiers — for example a3f90c1b7e2d8f45. Useful when downstream systems expect hex.

Numeric-only codes: set the alphabet to 0123456789 for short numeric codes — note that a 6-digit code from 10 symbols has far fewer possibilities than a 6-character ID from 64 symbols, so lengthen accordingly if collision matters.

Ambiguity-free: remove look-alike characters (0, O, I, l, 1) from the alphabet for codes that users may need to read and type back, such as short activation codes or vouchers.

Shorter IDs for low-volume apps: 12 characters from the 64-symbol alphabet is safe for most applications that will never generate more than a few million records. Test the collision odds against your expected ID count before going below 12.

Everything runs in your browser. The random bytes, your custom alphabet, and all generated IDs never leave your device.