Pure front-end local computing · Supports 6 ID formats

unique identifier generator UUID / ULID / Nano ID

Free, no-installation online unique ID generation tool. Supports six mainstream formats: UUID v4/v7, ULID, Nano ID, CUID2, and Short ID, and provides batch generation, repeated checking, and collision probability estimation. All operations are completed on the browser side to ensure data privacy and security.

1 1,000 max
ID length
character set
prefix
separation method
Output ready
Has produced: 0
Repeat: 0
Single length: 0

ID format comparison

Format Sortable URL security length chaos Features
UUID v4❌✅36 (32+4)⭐⭐⭐⭐⭐Purely random, most widely used
UUID v7✅✅36 (32+4)⭐⭐⭐⭐⭐Time-ordered, suitable for DB indexes
ULID✅✅26⭐⭐⭐⭐Crockford Base32, sortable
Nano ID❌✅Variable (default 21)⭐⭐⭐⭐⭐Lightweight and efficient, 64-character alphabet
CUID2❌✅about 24⭐⭐⭐⭐⭐Horizontal expansion safety, anti-collision
Short ID❌✅Variable (custom)⭐⭐⭐Short and flexible, customizable alphabet

Collision probability estimate

Estimate the probability of ID collision based on the number of IDs generated every day and the time of use.

≈ 0%

Estimated Collision Probability

Not calculated yet

Frequently Asked Questions

What is the difference between UUID, ULID and Nano ID?
UUID (v4) It is a 128-bit universal unique identification code, completely randomly generated, and widely used in database primary keys and distributed systems. However, due to its purely random nature, it is not suitable for B-tree indexing (it will cause page splits).

ULID It is also 128 bits, but the first 48 bits are timestamps, and the last 80 bits are random numbers, so it has "sortable" properties, and uses Crockford Base32 encoding, with a length of only 26 characters.

Nano ID Using a 64-character alphabet (A-Za-z0-9_-), a default length of 21 characters can achieve chaos similar to UUID v4. It is small in size and fast in speed, and is often used in scenarios such as URL shortening and file naming.
When should you use UUID v7 instead of UUID v4?
The core advantage of UUID v7 is "time ordering". The first 48 bits of v7 are the Unix millisecond timestamp, which makes the generated ID naturally monotonically increasing.

If your database uses B-tree or LSM-Tree as the index structure (such as PostgreSQL, MySQL, SQLite), using UUID v7 can significantly reduce the cost of index page splitting and random writing, and the performance can be improved by 5 to 10 times in large-scale insertion scenarios.

Scenarios where UUID v7 is recommended: Database primary keys, time series data, business scenarios that need to be sorted by creation time. UUID v4 is suitable for scenarios where sorting is not required and purely random identification is required.
Why can ULID be sorted?
The first 48 bits of the ULID store the Unix millisecond timestamp (similar to UUID v7), so sorting lexicographically is equivalent to sorting by creation time. This makes ULIDs more database index friendly than purely random IDs.

In addition, ULID uses Crockford Base32 encoding (excluding easily confused characters such as I, L, O, U, etc.), and the overall length is only 26 characters, which is more concise than the 36 characters of UUID. The encoding of the timestamp takes up the first 10 characters, and the last 16 characters are random numbers.

Another advantage of ULID is that it can generate up to 2^80 IDs in the same millisecond, and can still maintain uniqueness in extremely high concurrency scenarios.
Why is Nano ID becoming more and more popular?
The main reasons why Nano ID is popular among developers are as follows:

1. Very small body: The original code is only about 130 bytes (gzip), which has almost no impact on the front-end packaging volume.
2. High performance: Using Node.js’s crypto module or your browser’s Web Crypto API generates them much faster than a UUID.
3. Customization flexibility: You can freely adjust the ID length and character set to achieve the best balance between "uniqueness" and "conciseness".
4. URL security: By default, the URL safe character set (A-Za-z0-9_-) is used to embed URLs without additional encoding.
5. Adopted by mainstream projects: Frameworks including Next.js, Nuxt, Hono, and many open source projects use Nano ID as the default ID generation solution.
How to choose the appropriate ID format when building a system?
When choosing the ID format, you can judge based on the following points:

Requires time ordering and high security → UUID v7
Suitable for database primary keys, 128-bit randomness, supports global uniqueness.

Need time sorting but want to be more concise → ULID
26 characters, sortable, suitable for public identification.

Purely random identification, compatibility first → UUID v4
The most widely supported format, suitable for API, external system integration.

High-performance, lightweight front-end → Nano ID
Short, fast, and customizable, suitable for short-term tokens, file naming, and order numbers.

Requires security and horizontal scaling → CUID2
Designed specifically for horizontal expansion, with built-in collision protection mechanism.

Short and human-readable → Short ID
Suitable for invitation codes, coupon codes, short URL slugs.
What are the chances of an ID collision? Is it really not going to happen again?
This is a matter of probability, not "impossible" but "extremely difficult". Taking UUID v4 as an example, the number of effective bits is 122 bits. In theory, approximately 2.71 × 10^18 IDs must be generated to have a 50% collision probability (birthday paradox).

Converted into intuitive feeling:
• 1 billion UUID v4 are generated per second, with a collision probability of approximately 50% after 85 consecutive years
• With 1 million UUID v4 generated every second, the chance of seeing a collision in your lifetime approaches 0

ULID and Nano ID also have similar levels of security. You can use this tool's "collision probability estimation" function to calculate the specific collision risk based on your usage.
These IDs are generated purely by the front end. Are they really safe?
Yes, all ID generation logic of this tool uses the browser's Web Crypto API(crypto.getRandomValues / crypto.randomUUID), this is the cryptographically secure random number generator (CSPRNG) provided by the bottom layer of the operating system. It uses the same level of random number source as HTTPS encryption.

All calculations are done in your browser, the generated ID is not transmitted over the network, and no data is stored on the server. You can continue to use this tool after turning off the Internet.

If you need a higher security ID (for example, if it contains confidential information), it is recommended to use a dedicated library to generate it locally.

A closer look at unique identifiers: A complete guide from UUID to Nano ID

In modern software development, Unique Identifier is an important component that forms the basis of the system. Whether it's a database primary key, API resource identification, user ID, order number or file name, we need a reliable mechanism to generate unique identifiers.

UUID: The most widely used standard

UUID (Universally Unique Identifier) is a set of 128-bit identification code standards (RFC 4122). Its design goal is to ensure global uniqueness without the need for a central coordination mechanism. The most common UUID v4 relies entirely on random numbers, while the newer UUID v7 combines timestamps and random numbers to provide time-ordered features.

The advantage of UUID is that it has the highest degree of standardization and is natively supported by almost all programming languages and databases, making it very suitable for cross-system and cross-language application scenarios. However, its 36-character length can be verbose in some situations, and the purely random nature of v4 is not friendly to database indexes.

ULID: A modern alternative to sortable

ULID (Universally Unique Lexicographically Sortable Identifier) was proposed by Alizain Feerasta in 2016 to solve the problem of UUID being unsortable. The ULID is also 128 bits, but encoded as a 26-character Crockford Base32 string. Its timestamp prefix ensures that a lexicographic sort is a chronological sort and can produce up to 2^80 unique values ​​in the same millisecond.

The additional benefit of Crockford Base32 encoding is that it excludes easily confused characters (such as I, L, O, U), improving the accuracy of human reading and manual input. The case-insensitivity of ULIDs also makes them friendlier when used in URLs.

Nano ID: lightweight and efficient solution

Nano ID was developed by Andrey Sitnik (also the author of PostCSS and Autoprefixer) and is one of the most popular ID generators in the front-end ecosystem. Unlike UUID and ULID, Nano ID is not a fixed format standard, but a customizable implementation. Its core design philosophy is to "provide sufficient uniqueness in the smallest size."

Nano ID uses a 64-character URL safe alphabet (including A-Z, a-z, 0-9, - and _), and provides the same 126 bits of randomness as UUID v4 at a default length of 21 characters. By adjusting the length parameter, you can flexibly switch between safety and simplicity.

CUID2: horizontally extended anti-collision scheme

CUID2 is the second-generation version of CUID, built by Eric Elliott and specifically designed for horizontal scaling (Horizontal Scaling) scenarios. CUID2 internally uses incrementing counters, random fingerprints, and hash functions to ensure that collisions will not occur even in a decentralized system without a central coordinator.

The default length of CUID2 is about 24 characters and contains encoded fingerprint information, so even if two servers generate IDs within the same millisecond, the results will be completely different. This makes CUID2 ideal for microservice architectures and serverless applications.

How to choose? Practical suggestions

If you are creating a new PostgreSQL or MySQL table and want to use UUID as the primary key,It is strongly recommended to choose UUID v7, which can significantly reduce index fragmentation problems. If you need to expose the ID to the outside world and want it to be shorter,ULID or Nano ID is a better choice. For horizontal expansion scenarios with extremely high security requirements,CUID2 Provides additional protection against collisions.

No matter which format you choose, you can use ToolHub's ID generator to quickly generate test data and verify that your choice meets your business needs with the collision probability calculator.

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