Nano ID is a compact, URL-safe random identifier. By default it is 21 characters from a 64-symbol alphabet, giving collision resistance comparable to UUID v4 while being noticeably shorter and safe to drop straight into URLs.
Key takeaways
- Default Nano IDs are 21 URL-safe characters.
- Collision resistance is comparable to UUID v4 at the default size.
- Length is configurable, trading size against collision resistance.
For implementation context, continue with UUID vs Nano ID, Short UUID, and ULID. These pages cover the closest generator, comparison, validation or storage decisions without repeating this guide.
Why Nano ID
Nano ID was designed to be smaller and simpler than a UUID while staying safe in URLs, filenames and DOM ids. It uses a cryptographically strong random source and an unbiased selection algorithm, so shortening the alphabet or length does not skew the output.
It is a strong choice for public-facing identifiers where a 36-character UUID feels heavy and you control both ends of the system.
Choosing a length
The default of 21 characters is a good balance for most applications. Shorter IDs are prettier but raise collision risk as you generate more of them, so tune the length deliberately for high-volume use and keep a database uniqueness constraint either way.