UUID (Universally Unique Identifier) and NanoID are both solutions for generating unique identifiers without a central coordinating authority, but they differ in design philosophy, format, and ecosystem support. UUID is a formal standard defined in RFC 4122 (and updated in RFC 9562), producing 128-bit identifiers represented as 36-character hexadecimal strings with hyphens (e.g., 550e8400-e29b-41d4-a716-446655440000). NanoID is a modern JavaScript library that generates 21-character URL-safe strings using a 64-character alphabet, producing identifiers like V1StGXR8_Z5jdHi6B-myT.
The entropy difference is minimal in practice. UUID v4 uses 122 random bits (6 bits are reserved for version and variant flags). NanoID's default 21-character output with a 64-character alphabet provides 126 bits of entropy. Both offer collision probabilities so low that generating a duplicate in a single system is effectively impossible within any practical timeframe. You would need to generate over a billion IDs per second for decades to reach a 50% probability of a single collision with either format.
The practical differences lie in string length, character set, and ecosystem. NanoID's 21-character output is 42% shorter than UUID's 36-character format, which matters in URLs, localStorage keys, and bandwidth-sensitive contexts. NanoID's URL-safe alphabet eliminates the need for encoding, while UUIDs contain hyphens that must be handled in URL path segments. In JavaScript, the nanoid package is approximately 130 bytes after minification and gzip, compared to the uuid package's 6.5 KB, a meaningful difference for client-side bundles.
Where UUID excels is infrastructure integration. PostgreSQL has a native UUID type with optimized B-tree and hash indexing. MySQL 8.0 added UUID-related functions. ORMs across every language support UUID primary keys out of the box. Interoperability between services, databases, and third-party systems is seamless with UUIDs because every language and platform understands the format. NanoID strings are stored as VARCHAR, lack native database type support, and require the NanoID library or a compatible implementation on both sides of any system boundary.
| Feature | UUID | NanoID |
|---|---|---|
| String length | 36 characters (with hyphens) | 21 characters (default, customizable) |
| Character set | Hexadecimal (0-9, a-f) plus hyphens | URL-safe A-Za-z0-9_- (64 chars) |
| Collision probability | Extremely low (122 random bits for v4) | Comparable (126 bits of entropy default) |
| Standardization | RFC 4122, universally supported | No formal standard, library-defined |
| Database compatibility | Native UUID type in PostgreSQL, MySQL 8+ | Stored as VARCHAR, no native type |
| URL friendliness | Requires encoding hyphens in some contexts | URL-safe by default, no encoding needed |
| Sort order (time-based) | UUIDv7 is time-sortable | Not time-sortable by default |
| Generation speed | Fast with crypto.randomUUID() | Slightly faster, fewer bytes to generate |
| Bundle size (JS) | uuid package is ~6.5 KB | nanoid is ~130 bytes (50x smaller) |
| Cross-language support | Available in every programming language | JavaScript-first, ports exist for other langs |
Use UUID when interoperability with databases, external systems, and industry standards matters. PostgreSQL native UUID type, database indexing, and universal library support make UUIDs the safe default for backend systems. Use NanoID for frontend-generated IDs, URL slugs, client-side state management, and applications where smaller bundle size and shorter strings provide tangible benefits.
Choose UUID when your identifiers cross system boundaries. If your IDs are stored in PostgreSQL, referenced by external APIs, included in OpenTelemetry traces, or shared between microservices written in different languages, UUID's standardization eliminates friction. Every database, ORM, logging framework, and monitoring tool understands UUIDs natively. Consider UUIDv7 (time-ordered) if you need identifiers that are both unique and chronologically sortable for database indexing performance.
Choose NanoID when the identifiers are primarily consumed within your JavaScript application. Frontend-generated IDs for React component keys, temporary state identifiers, URL-safe slugs, and client-side database keys (IndexedDB, localStorage) benefit from NanoID's shorter length, URL-safe characters, and tiny bundle footprint. If your entire stack is JavaScript and the IDs never leave the application, NanoID's pragmatic design is a good fit.
Consider the database impact. PostgreSQL stores UUIDs as 16 bytes internally regardless of the 36-character string representation, making them efficient for indexing and storage. NanoID strings stored as VARCHAR(21) use 22 bytes with the length prefix, slightly larger but comparable. However, UUID's native type enables specialized indexing and comparison operations that VARCHAR cannot match. For tables with millions of rows where the identifier is the primary key and frequently queried, UUID's native type provides measurable performance benefits.
Generate and inspect UUIDs with the PinusX UUID Generator, which supports both v4 (random) and v7 (time-ordered) formats with 100% client-side processing. Your generated identifiers are never sent to any server, ensuring they remain private even during development and testing.
Yes, NanoID's default 21-character output provides 126 bits of entropy, making collision probability negligible for any practical database size. However, NanoID lacks native database type support, so IDs are stored as VARCHAR, which uses slightly more storage and has slower comparisons than PostgreSQL's native UUID type. For small to medium applications, NanoID primary keys work fine.
Yes, NanoID allows you to specify both the length and the character alphabet. You can generate shorter IDs for less critical use cases (like URL slugs) or longer IDs for higher entropy. Custom alphabets let you exclude ambiguous characters or restrict to specific character sets. The entropy calculation adjusts automatically based on your configuration.
UUIDv7 is the recommended choice for new projects that use UUIDs as database primary keys. UUIDv7 includes a timestamp prefix that makes IDs chronologically sortable, significantly improving B-tree index performance for INSERT-heavy workloads. UUIDv4 is fully random and appropriate when time-ordering is unnecessary or when you want no timing information embedded in the identifier.
Yes, NanoID works in both environments. It uses the Web Crypto API (crypto.getRandomValues) in browsers and the Node.js crypto module on the server, ensuring cryptographically secure random generation in both contexts. The package exports both synchronous and asynchronous APIs, and the bundle size is only 130 bytes in the browser.
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