CUID vs UUID: Which Should You Use?
A comprehensive comparison of unique identifier formats to help you make the right choice for your project.
Quick Comparison
| Feature | CUID v1 | CUID2 | UUID v4 |
|---|---|---|---|
| Length | 25 chars | 24 chars | 36 chars |
| Format | c[a-z0-9]24 | [a-z0-9]24 | xxxxxxxx-xxxx-... |
| URL Safe | ✓ | ✓ | ✗ (hyphens) |
| Sortable by Time | ✓ (roughly) | ✗ | ✗ |
| Contains Timestamp | ✓ | ✗ | ✗ |
| Crypto Secure | ✗ | ✓ | ✓ |
| Configurable Length | ✗ | ✓ (2-32) | ✗ |
| Standard/RFC | ✗ | ✗ | ✓ (RFC 4122) |
Format Examples
cjld2cjxh0000qzrmn831i7rntz4a98xxat96iws9zmbrgj3a550e8400-e29b-41d4-a716-446655440000Detailed Comparison
📏 Size & Storage
CUIDs are more compact than UUIDs, which matters for storage and bandwidth:
- •CUID2 (24 chars) saves 12 characters per ID vs UUID
- •For 1 million records: ~12 MB less storage with CUID2
- •Smaller IDs = faster indexing and lookups
🔗 URL Safety
CUIDs are designed to be URL-safe out of the box:
/users/tz4a98xxat96iws9zmbrgj3a/users/550e8400-e29b-41d4-a716-446655440000⚡ Performance
Both CUID and UUID v4 are fast to generate, but they have different performance characteristics:
| Operation | CUID | UUID |
|---|---|---|
| Generation Speed | ~100k/sec | ~200k/sec |
| Index Size | Smaller | Larger |
| Sort Performance | Good (time-based) | Poor (random) |
🔐 Security
Security considerations differ between versions:
⚠️ Timestamp is extractable, creation order is guessable. Not recommended for security-sensitive applications.
✓ Cryptographically secure, no predictable patterns. Safe for sessions, tokens, and sensitive IDs.
✓ Cryptographically random. Widely used and trusted for security-sensitive applications.
🌐 Portability & Standards
UUID has a significant advantage in standardization:
- •UUID is defined by RFC 4122 and universally supported
- •Many databases have native UUID types with optimized storage
- •CUID is stored as a string in most databases
- •Some APIs and libraries specifically require UUID format
When to Use Each
Use CUID v1 when...
- ✓ You need rough time-based sorting
- ✓ Timestamp extraction is useful
- ✓ URL-safe IDs are required
- ✓ Security is not a primary concern
Use CUID2 when...
- ✓ Security is important
- ✓ You want shorter IDs
- ✓ URL-safe IDs are required
- ✓ Custom length is needed
- ✓ Starting a new project
Use UUID when...
- ✓ Standards compliance is required
- ✓ Integrating with UUID-only systems
- ✓ Using native UUID database types
- ✓ Maximum interoperability needed
Other Alternatives
CUID and UUID aren't your only options. Here are other popular formats:
| Format | Length | Key Feature |
|---|---|---|
| ULID | 26 chars | Lexicographically sortable (timestamp-first) |
| NanoID | 21 chars | Very compact, customizable alphabet |
| Snowflake | 64-bit int | Twitter's format, strictly sortable |
| KSUID | 27 chars | K-Sortable, timestamp included |
| UUID v7 | 36 chars | Time-ordered UUID (new standard) |
Conclusion
Both CUID and UUID are excellent choices for generating unique identifiers. The best choice depends on your specific requirements:
- →Choose CUID2 for most modern applications — it's secure, compact, and URL-safe.
- →Choose UUID when you need maximum compatibility or are working with systems that require it.
- →Choose CUID v1 only if you specifically need the embedded timestamp feature.