CUID Generator
Generate collision-resistant CUIDs instantly in your browser. No server, no signup, and no dependencies.
CUID Generator
Powered bycrypto.getRandomValues()
All CUIDs are generated locally using secure randomness; nothing is sent to a server.
Your CUIDs will appear here.
Set a quantity and click Generate.
What is a CUID?
A CUID (Universally Unique Identifier) is a 128-bit identifier used to uniquely identify information in computer systems without centralized coordination. It is standardized by RFC 4122 and represented as a 32-character hexadecimal string split into 5 groups separated by hyphens.
Length
36 characters — 32 hex digits + 4 hyphens
Randomness
122-bit entropy — ~5.3 × 1036 possible values
Standard
RFC 4122 — also ITU-T X.667 and ISO/IEC 9834-8
What is a CUID?
A CUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit label standardized by the Internet Engineering Task Force under RFC 4122.
CUIDs are designed to be unique across all time and space without requiring a central registration authority. Two independently generated CUIDs can be assumed to be distinct, thanks to their extreme statistical uniqueness.
- 128 bits = 16 bytes of data
- Represented as 32 hex digits + 4 dashes (36 chars)
- Case-insensitive — upper or lowercase are equivalent
- Supported natively in PostgreSQL, MySQL, MongoDB, and more
CUID Format
A CUID starts with c, then includes a timestamp, a counter, a small client fingerprint, and random bytes to minimize collisions.
CUID vs CUID
A quick comparison to help you choose the right identifier for your project.
| Identifier | Format | Strengths | Best for |
|---|---|---|---|
| CUID | c + timestamp + counter + fingerprint + random |
Short, collision-resistant, URL-safe | Web apps, databases, distributed systems |
| CUID v4 | Random 128-bit value (RFC 4122) | Widely supported, large namespace | APIs, tokens, general-purpose identifiers |
Example CUIDs Generated Today
Fresh CUIDs generated client-side on page load. Click any to copy.
How This CUID Generator Works
This tool generates CUIDs entirely in your browser using the Web Crypto API (crypto.getRandomValues()). Everything runs locally — no data is sent to a server.
Each CUID is designed to be collision-resistant while remaining short and URL-safe. The generator assembles IDs using a combination of timestamp, counter, fingerprint, and random bytes:
- Start with the letter
c(CUID prefix) - Add the current timestamp in base36
- Append an incrementing counter to avoid same-millisecond collisions
- Add a small fingerprint derived from the browser environment
- Append random bytes for extra entropy
Common Use Cases
CUIDs are the preferred unique identifier for:
Frequently Asked Questions
Concise answers about CUIDs and this generator tool.
c1kq9ud3z00001dv8n3v7a2c. It is typically 25–26 characters long and uses a URL-safe base36 alphabet (0-9a-z).
crypto.getRandomValues() API.
crypto.getRandomValues() API, which is cryptographically secure. All generation happens locally in your browser — no data is sent to any server, and the generated CUIDs are never logged, stored, or transmitted.
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