21 characters from the 64-character base64url set (A–Z, a–z, 0–9, - and _) — about 126.0 bits of entropy per ID. Reaching a 1% chance of any two IDs matching takes roughly 10^18 of them. These IDs come from a seeded, non-cryptographic PRNG so that a shared link always renders the same list. The real Nano ID library draws from the platform CSPRNG instead; use it, or crypto.getRandomValues, for anything that has to be unguessable.
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21 characters from the 64-character base64url set (A–Z, a–z, 0–9, - and _) — about 126.0 bits of entropy per ID. Reaching a 1% chance of any two IDs matching takes roughly 10^18 of them. These IDs come from a seeded, non-cryptographic PRNG so that a shared link always renders the same list. The real Nano ID library draws from the platform CSPRNG instead; use it, or crypto.getRandomValues, for anything that has to be unguessable.
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Tentang nano id
Nano ID is a reaction to two things about UUIDs: how long they are, and how badly they fit in a URL. The canonical form is 36 characters, four of them hyphens, and the remaining 32 are drawn from an alphabet of only sixteen — hexadecimal is a wasteful way to carry randomness. The alternative had been standing in plain sight since October 2006, when Simon Josefsson's RFC 4648 specified a URL- and filename-safe variant of base64 that swaps + and / for - and _, so an encoded value survives a path segment, a query string and a filesystem untouched.
Andrey Sitnik, better known for PostCSS and Autoprefixer, published Nano ID in 2017 on exactly that basis. The defaults encode a set of deliberate judgements. Twenty-one characters from a 64-character alphabet give 126 bits, slightly more than the 122 random bits in a version 4 UUID, in fifteen fewer characters. Randomness comes from the platform's cryptographic generator — crypto.getRandomValues in a browser, crypto.randomBytes in Node — rather than Math.random, with a separate nanoid/non-secure entry point for callers who would rather have the speed and know what they are giving up. For custom alphabets the implementation masks bits and discards out-of-range samples instead of taking a modulo, which would quietly over-represent the first characters of any alphabet whose size is not a power of two.
It displaced its predecessor fairly completely: the older shortid package is now deprecated on npm with a note pointing at Nano ID. Ports followed for Go, Rust, Python, Java, PHP, Ruby, Swift and many other languages, and version 4 of the JavaScript package dropped CommonJS support, which left a long tail of projects on version 3.
The trade-off is explicit. A Nano ID holds no timestamp, counter or machine identifier, so it leaks nothing about where or when it was made — and sorts in no useful order at all, the opposite of the choice UUID version 7 and MongoDB's ObjectId make.
Sifat utama
The default alphabet is 64 characters — A–Z, a–z, 0–9, hyphen and underscore — which is the base64url set defined in RFC 4648 section 5.
The default length is 21 characters, which at 6 bits per character is exactly 126 bits of entropy.
A 21-character Nano ID carries 126 bits against a version 4 UUID’s 122, in 21 characters rather than 36.
Every character of the default alphabet is safe unescaped in a URL path, a query string, a filename and an HTML attribute.
At 1,000 IDs per hour, reaching a 1% chance of a single collision takes roughly 149 billion years at the default length — the figure quoted by the library’s own collision calculator.
Because 64 divides 256, the default alphabet needs no bias correction; the rejection-sampling path in the reference implementation exists for alphabets whose size is not a power of two.
A Nano ID contains no timestamp, counter or machine identifier, so the IDs neither sort by creation time nor disclose anything about their origin.
The IDs on this page are generated from a seeded, non-cryptographic PRNG, which makes them reproducible from the URL and therefore unsuitable as real identifiers.