CUID2 is a modern identifier standard designed to fix the security and scalability flaws of UUIDv4 and original CUID. It generates URL-safe strings that are cryptographically collision-resistant and safe against offline attacks.

Why use CUID2 instead of UUIDv4?

Unlike UUIDv4, CUID2 is highly optimized for databases (reducing B-Tree fragmentation) and is entirely URL-safe (no hyphens). It is the default identifier used in modern ORMs like Prisma.

Free CUID2 Generator Online (Secure & URL-Safe Identifiers) [2026]

A secure random ID generator for web applications

CUID2 is the next-generation identifier standard designed specifically to address the security flaws found in UUIDv4 and the original CUID specification. If you need a secure random ID generator for web applications, CUID2 provides highly secure, scalable, and URL-safe strings that cannot be guessed or sequentially attacked.

Today, CUID2 is the recommended standard in modern web development frameworks and is used heavily as the default primary key generator in ORMs like Prisma. Need mock data? Use our Bulk Cuid2 generator for database testing above to instantly generate up to 10,000 IDs.

Cuid2 vs Nanoid for database primary keys

Standard UUID generators create strings like 550e8400-e29b-41d4-a716-446655440000. While perfectly valid, they suffer from three major issues that CUID2 solves. When comparing Cuid2 vs Nanoid for database primary keys, CUID2 often wins out for backend persistence due to these optimizations:

URL Safety: UUIDs contain hyphens, meaning if you double-click them in a URL bar or terminal, your computer only highlights a segment of the ID. CUID2 strings (e.g., tz4a98xxat96iwsflptntm8m) are contiguous lowercase strings. Double-clicking highlights the entire ID instantly.
Database Performance: Random UUIDv4s cause severe B-Tree index fragmentation in SQL databases because they are entirely random. CUID2 mitigates this by maintaining a degree of horizontal scalability without fully sacrificing performance.
Security & Offline Attacks: Original CUIDs leaked the MAC address and timestamp of the generating machine. CUID2 uses cryptographic hashing to completely obfuscate the host machine, making offline enumeration attacks impossible.

Customizing CUID2 Length

One of the greatest features of CUID2 is variable length formatting. The official specification defaults to 24 characters, which provides enough entropy (randomness) to ensure zero collisions even at planetary scale.

However, if you are building a small-scale application, you can safely slide the length down to 10 or 12 characters to save database storage space and keep your URLs incredibly short, while still maintaining more security than a standard NanoID.