Numbers

CUID-Style ID Generator

The CUID-style ID generator creates collision-resistant unique identifiers built for modern databases, distributed systems, and APIs. Unlike UUIDv4, which is entirely random, CUID-format IDs embed a timestamp component at the front, so records inserted into a database sort roughly in creation order without any extra indexing tricks. That property alone makes them a practical choice for high-throughput applications where you need both uniqueness and chronological ordering out of the box. Each generated ID uses only lowercase alphanumeric characters, which means it drops cleanly into URLs, JSON payloads, and file names without encoding headaches. The optional prefix letter lets you namespace IDs by entity type — 'u' for users, 'o' for orders, 'p' for products — giving you a quick visual signal about what a given ID refers to when debugging logs or inspecting a database directly. This tool is aimed at backend developers, API designers, and anyone prototyping a data model who needs a batch of realistic unique IDs fast. You can generate up to a large count in one click and copy the whole list for seeding test databases, populating fixture files, or filling out API documentation examples with real-looking identifiers. CUID-style IDs strike a balance between the strict randomness of UUID and the fragile predictability of auto-increment integers, making them a solid default for primary keys in horizontally scaled systems where multiple nodes may be writing simultaneously.

How to Use

  1. Set the count field to how many CUID-style IDs you need, for example 10 for a database seed batch.
  2. Enter a prefix letter that matches your entity type, such as 'u' for users or 'p' for products.
  3. Click Generate to produce the full list of unique IDs instantly.
  4. Copy the output list and paste it directly into your fixture file, seed script, or API docs.

Use Cases

  • •Seeding a test database with realistic-looking primary keys
  • •Generating entity-prefixed IDs like 'u_...' for users or 'o_...' for orders
  • •Creating URL-safe tokens for shareable resource links
  • •Populating API documentation examples with real-format identifiers
  • •Assigning IDs to distributed log events that need rough time ordering
  • •Building fixture files for frontend or backend integration tests
  • •Prototyping a new data model before a database is even set up
  • •Replacing auto-increment IDs in a multi-node write architecture

Tips

  • →Use a different prefix per entity type in the same project — it makes raw database dumps dramatically easier to read.
  • →When seeding a relational database, generate IDs for parent records first so you can reference them in child fixture rows.
  • →If you need IDs for API documentation, generate 3–5, then hardcode them as constants so examples stay consistent across doc pages.
  • →CUIDs sort well in most B-tree indexes because the timestamp prefix reduces page splits — prefer them over UUIDv4 for write-heavy tables.
  • →Paste a batch into a spreadsheet column to quickly build a mock dataset with realistic-looking IDs alongside other generated data.
  • →If your framework enforces a specific ID length, verify the output length first — CUID and CUID2 differ in length, so check compatibility before committing to a schema.

FAQ

What is a CUID-style ID?

A CUID (Collision-Resistant Unique Identifier) is a string ID designed for distributed systems. It starts with a prefix letter, followed by a timestamp component, a fingerprint, and random characters. The timestamp prefix means IDs sort roughly in creation order, which is useful for database indexing and debugging sequential events.

How is a CUID different from a UUID?

UUIDv4 is fully random, offering no time ordering. CUIDs embed a timestamp at the start, so rows inserted into a database index in roughly chronological order without extra effort. CUIDs are also lowercase alphanumeric only, avoiding the hyphens in UUIDs that can cause issues in certain URL or variable-name contexts.

Are CUID-style IDs safe to use in URLs?

Yes. They use only lowercase letters and digits — no hyphens, underscores, or special characters. You can place them directly in URL path segments or query strings without percent-encoding. This makes them a practical choice for REST API resource identifiers like /orders/o8xk2m... .

Can I change the prefix letter and what should I use?

Yes — type any single letter into the prefix field. A common convention is to use the first letter of your entity: 'u' for users, 'p' for products, 'o' for orders, 'e' for events. This gives anyone reading a raw ID an immediate hint about what entity it belongs to, which speeds up debugging.

Are these IDs truly unique or could two be the same?

Collisions are extremely unlikely. The design combines a timestamp, a per-process counter, a host fingerprint, and random characters. In practice, you would need an astronomically large number of concurrent inserts per millisecond on the same machine to produce a collision. For most applications, they are safe to treat as unique without a uniqueness check.

How many CUIDs should I generate at once?

Generate as many as your immediate task requires. For seeding a test database, generate the exact count of rows you need. For documentation, 3–5 examples is usually enough. Generating a large batch is fine — just paste the list directly into a fixture file or split it with a script.

Can I use these IDs in JavaScript or Node.js projects directly?

These generated IDs match the CUID format, so they are compatible as static values in any project. If you need IDs generated at runtime in code, install the 'cuid' or 'cuid2' npm package. Use this generator for seeding, testing, or documentation where you need pre-made IDs rather than runtime generation.

Do CUID-style IDs reveal any sensitive information?

The timestamp component does encode approximate creation time, which is worth knowing. If exposing the exact creation timestamp in a public-facing ID is a concern, consider using a fully random format like UUIDv4 instead. For internal systems and most APIs, the time component is harmless and actively useful.