UUID Generator - Free Online Tool
Generate, validate, and decode UUIDs online. Our free UUID generator supports v1, v4, and v7 with bulk generation, validation, and code snippets for 10+ programming languages.
What is a UUID? Complete Guide to Universally Unique Identifiers
A UUID (Universally Unique Identifier) is a 128-bit number used to identify information in computer systems. The term GUID (Globally Unique Identifier) is also used, particularly in Microsoft systems.
UUID Format
A standard UUID looks like this: 550e8400-e29b-41d4-a716-446655440000
It consists of 32 hexadecimal digits, displayed in five groups separated by hyphens, in the form 8-4-4-4-12 for a total of 36 characters.
UUID Versions
UUID v1 (Time-based)
Generated using the current timestamp and the computer's MAC address. While unique, it can expose the machine's identity and creation time.
UUID v4 (Random)
The most commonly used version. Generated using random or pseudo-random numbers, providing excellent uniqueness without exposing system information.
UUID v5 (Name-based with SHA-1)
Generated using a namespace identifier and a name, using SHA-1 hashing. Deterministic - same input always produces the same UUID.
When to Use UUIDs
UUIDs are ideal when you need:
- Globally unique identifiers across distributed systems
- Identifiers that don't require central coordination
- Primary keys in databases that will be merged
- Unique filenames or object identifiers
- Session identifiers or API keys
UUID Best Practices
- Use UUID v4 for most cases - It's random, secure, and doesn't leak information
- Store as binary in databases - Save space by storing as BINARY(16) instead of VARCHAR(36)
- Index properly - UUID columns should be indexed if used for lookups
- Don't use for sequential IDs - UUIDs are random and can hurt database performance for ordered inserts
Common Misconceptions
"UUIDs are guaranteed unique" - While collision is astronomically unlikely (1 in 2^122), it's theoretically possible.
"All UUIDs are random" - Only v4 is truly random. v1, v3, and v5 are deterministic based on inputs.
"UUIDs are secure tokens" - While v4 UUIDs are hard to guess, they shouldn't be used as secret tokens without additional security measures.
UUID v4 vs v1: Which Should You Use?
Choosing between UUID v4 (random) and UUID v1 (time-based) is a common decision when designing systems. Let's break down the differences.
UUID v1: Time-Based UUIDs
How it works: Combines the current timestamp with the MAC address of the machine generating the UUID.
Pros:
- Chronologically sortable (useful for databases)
- Can extract creation timestamp
- Slightly faster to generate (no random number generation needed)
Cons:
- Exposes MAC address (privacy/security concern)
- Reveals creation time (information leakage)
- Requires unique clock sequence handling
- Can have collisions if system clock changes
UUID v4: Random UUIDs
How it works: Generated using random or pseudo-random numbers. 122 bits of randomness.
Pros:
- No information leakage
- Better privacy and security
- Simple to implement
- Works in any environment
- No coordination needed between systems
Cons:
- Not sortable by creation time
- Requires good random number generator
- Slightly slower to generate
Performance Comparison
Generation Speed:
- v1: ~1,000,000 UUIDs per second
- v4: ~500,000 UUIDs per second
For most applications, this difference is negligible. Network I/O and database operations are typically the bottleneck.
Security Considerations
UUID v1 should NOT be used for session tokens, security tokens, or any case where predictability is a concern. The timestamp and MAC address make v1 UUIDs partially predictable.
UUID v4 is cryptographically random and suitable for most security applications, though purpose-built cryptographic tokens are better for high-security scenarios.
Recommendations
Use UUID v4 when:
- Security and privacy matter
- You're building a distributed system
- You want a simple, safe default
- You're generating IDs for public APIs
Use UUID v1 when:
- You need time-ordered IDs
- Database insert performance is critical
- You're in a controlled environment
- Privacy concerns don't apply
Conclusion: For most modern applications, UUID v4 is the safer choice. Its simplicity, security, and privacy benefits outweigh the minor performance trade-offs.
How to Store UUIDs in Databases Efficiently
UUIDs are excellent for distributed systems, but storing them efficiently in databases requires careful consideration. Let's explore the best practices.
Storage Format Options
Option 1: VARCHAR(36) - String Format
CREATE TABLE users (
id VARCHAR(36) PRIMARY KEY,
name VARCHAR(255)
);
Pros: Easy to read and debug, works everywhere, simple to use in queries
Cons: Wastes space (36 bytes vs 16 bytes), slower comparisons, poor cache locality
Option 2: BINARY(16) - Binary Format
CREATE TABLE users (
id BINARY(16) PRIMARY KEY,
name VARCHAR(255)
);
Pros: Efficient storage (16 bytes), faster comparisons, better cache utilization
Cons: Harder to debug (shows as hex), requires conversion functions, not human-readable
Option 3: Database-Native UUID Types
PostgreSQL:
CREATE TABLE users (
id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
name VARCHAR(255)
);
MySQL 8.0+:
CREATE TABLE users (
id BINARY(16) PRIMARY KEY DEFAULT (UUID_TO_BIN(UUID())),
name VARCHAR(255)
);
Performance Comparison
Storage space for 1 million UUIDs:
- VARCHAR(36): ~36 MB
- BINARY(16): ~16 MB
- Savings: 55%
Query performance (SELECT WHERE id = ?):
- VARCHAR(36): 100% (baseline)
- BINARY(16): ~60% (40% faster)
Index Performance
Random UUIDs (v4) cause index fragmentation because they're not sequential. This affects INSERT performance. Solutions include using ordered UUIDs, ULID (Universally Unique Lexicographically Sortable Identifier), or separate sequential and UUID keys.
Conversion Functions
MySQL:
-- String to Binary
UUID_TO_BIN('550e8400-e29b-41d4-a716-446655440000')
-- Binary to String
BIN_TO_UUID(binary_uuid)
PostgreSQL:
-- Already native UUID type
SELECT '550e8400-e29b-41d4-a716-446655440000'::uuid;
Best Practices
- Choose binary storage when possible - 55% space savings is significant
- Use database-native UUID types - PostgreSQL's UUID type is excellent
- Index UUID columns - Essential for foreign keys and lookups
- Consider ordered UUIDs for high-write scenarios - Reduces fragmentation
- Document your choice - Make it clear to future developers
- Benchmark your specific use case - Real data matters more than general advice
Real-World Recommendations
For PostgreSQL: Use native UUID type. It's clean, efficient, and well-supported.
For MySQL: Use BINARY(16) with UUID_TO_BIN() and BIN_TO_UUID() functions in MySQL 8.0+.
For other databases: Use BINARY(16) if supported, VARCHAR(36) if binary support is poor.
Conclusion: Efficient UUID storage is about choosing the right format for your use case. Binary storage offers significant benefits, but requires more careful implementation. For most modern applications, the performance gains are worth the extra complexity.
UUID Generator Features
- Multiple UUID versions: Generate v1, v4, and v7 UUIDs
- Bulk generation: Create up to 1,000 UUIDs at once
- Validation: Check if a UUID is valid and decode its information
- Multiple formats: Standard, no-hyphens, uppercase, braces, URN
- Export options: TXT, CSV, JSON, SQL formats
- Code snippets: Get UUID generation code in 10+ languages
- Comparison tool: Compare and analyze UUIDs
- Privacy-first: All processing happens in your browser
- Free forever: No registration, no limits, no cost
Frequently Asked Questions
Is this UUID generator really free?
Yes! Our UUID generator is completely free to use with no limitations. Generate as many UUIDs as you need, use all features, and never pay a cent.
Are the UUIDs truly unique?
UUIDs have a 1 in 2^122 chance of collision, making duplicates astronomically unlikely. For all practical purposes, they are unique.
Can I use these UUIDs in production?
Absolutely. Our generator uses industry-standard algorithms and is suitable for production use in databases, APIs, and distributed systems.
Is my data sent to your servers?
No. All UUID generation happens directly in your browser using JavaScript. Your data never leaves your device, ensuring complete privacy.
Which UUID version should I use?
For most cases, use UUID v4 (random). It's secure, doesn't leak information, and works everywhere. Use v1 only if you need time-ordered IDs and understand the privacy implications.
Can I generate bulk UUIDs?
Yes! Our tool supports bulk generation of up to 1,000 UUIDs at once. Perfect for database seeding or testing.
What programming languages do you support?
We provide code snippets for JavaScript, Python, Java, C#, PHP, Ruby, Go, Rust, Swift, Kotlin, and more.
Do I need to install anything?
No installation needed. UUID Generator works directly in your web browser on any device - desktop, tablet, or mobile.
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