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UUID Generator

Generate unique UUIDs (Universally Unique Identifiers)

Generate UUIDs

Create one or multiple UUIDs at once

Generated UUIDs (0)

About UUIDs

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. The probability of generating duplicate UUIDs is negligibly small.

Why Use This Tool?

  • ✓ Generate guaranteed unique identifiers for database records without coordination - no need for centralized ID servers or auto-increment sequences, perfect for distributed systems where multiple servers create records simultaneously without collisions
  • ✓ Create unguessable IDs for security-sensitive resources (API keys, session tokens, file upload names) - unlike sequential IDs that reveal system information (user count, creation order), UUIDs provide no predictable pattern preventing enumeration attacks
  • ✓ Enable offline data creation with merge-later workflow - generate IDs on mobile apps, browser storage, or disconnected devices, sync to server later without ID conflicts (impossible with auto-increment IDs requiring database connection)
  • ✓ Maintain data privacy when sharing logs or analytics - UUIDs don't leak business metrics like sequential IDs (order #100,000 tells competitor your volume), safe to expose in URLs and error messages without revealing sensitive counts
  • ✓ Instant generation with zero database round-trips - create hundreds of IDs client-side in milliseconds for batch operations, test data generation, or temporary identifiers without hitting database for each ID request

UUID Format

  • Format: \text{xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx}
  • 128-bit number (32 hexadecimal digits)
  • Version 4 (random): 2^{122} possible UUIDs
  • Collision probability: \approx 10^{-18} for 1 billion UUIDs
  • Structure: time-low, time-mid, time-hi-version, clock-seq, node

UUID Version 4

  • This tool generates Version 4 UUIDs, which are randomly generated. The 4 most significant bits of the 7th byte are set to 0100 (version 4), and the 2-3 most significant bits of the 9th byte are set to 10 (variant 1).

Common Uses

  • Database primary keys
  • Session identifiers
  • Unique file names
  • API request tracking
  • Distributed systems coordination

Common Questions

  • Q: Should I use UUIDs or auto-increment integers for database primary keys? Depends on use case. Auto-increment (1, 2, 3...): Pros: smaller (4-8 bytes vs 16 bytes UUID), faster indexes, better for single-database systems, human-readable for debugging. Cons: reveals business metrics (record count, creation rate), enables enumeration attacks (iterate IDs to scrape all records), requires database coordination (breaks in distributed systems, merge conflicts). UUIDs: Pros: globally unique without coordination, works in distributed/offline systems, security through obscurity (can't guess valid IDs), safe in URLs. Cons: larger storage/index size (2-4x overhead), slower lookups, not human-friendly. Use UUIDs when: distributed database, multi-tenant system, offline-first apps, public-facing IDs in URLs. Use auto-increment when: single database, internal-only IDs, storage/performance critical.
  • Q: What's the difference between UUID v1, v4, and v5? v1 (timestamp-based): includes MAC address and timestamp, sortable by creation time, predictable (security issue), reveals machine identity (privacy issue). Don't use unless you specifically need time-ordering. v4 (random): completely random, most common, unpredictable, no information leakage, this tool generates v4. Use for general purpose unique IDs. v5 (name-based/SHA-1): deterministic - same input always produces same UUID, useful for generating consistent IDs from names (user email → UUID), reproducible but not random. Use when you need consistent IDs derived from existing data. For 99% of use cases, v4 is correct choice.
  • Q: Can two people generate the same UUID? Probability is astronomically small - 1 in 2^122 (5.3×10^36) for UUIDv4. To put in perspective: generating 1 billion UUIDs per second for 85 years has only 0.00000005% chance of collision. Realistically: zero chance of collision in any normal application lifetime. More likely: hardware failure, software bug, or meteor strike than UUID collision. In practice, treat UUIDs as guaranteed unique. Exception: poor random number generator implementation (use cryptographically secure RNG for UUID generation, which this tool and standard libraries do).
  • Q: Are UUIDs safe to use in URLs or as filenames? Yes, UUIDs use only hexadecimal characters (0-9, a-f) and hyphens, which are URL-safe and filename-safe on all operating systems (Windows, Mac, Linux). No special encoding needed. Examples: `https://api.com/users/550e8400-e29b-41d4-a716-446655440000` (no escaping required), filename `report-550e8400-e29b-41d4-a716-446655440000.pdf` (works everywhere). If you need shorter URLs, remove hyphens (still valid UUID) or use base64 encoding (reduces 36 chars to ~22 chars). Never use sequential IDs in public URLs - reveals record count and enables enumeration attacks.
  • Q: Do UUIDs hurt database performance compared to integers? Yes, but usually negligible for most applications. Performance impacts: (1) Storage: UUID = 16 bytes, int = 4 bytes, bigint = 8 bytes. For 1 million records: 12MB overhead with UUIDs vs bigint. (2) Index size: larger keys = larger indexes = more disk I/O. (3) Random inserts: UUID inserts are random (no sequential order) causing B-tree page splits, vs auto-increment's append-only pattern. (4) Join performance: larger keys slower to compare. Real-world impact: for most applications (<10M records, <1000 queries/sec), difference is <10ms per query - acceptable. Optimize: use BINARY(16) not CHAR(36) in MySQL (saves 20 bytes), consider UUIDv1 for time-ordered inserts, add auto-increment surrogate key if needed. Don't prematurely optimize - use UUIDs if they solve architectural problems.

Pro Tips & Best Practices

  • 💡 Use UUIDs as primary keys in distributed or multi-tenant databases: In distributed systems (microservices, sharded databases, multi-region setups), auto-increment IDs require coordination causing bottlenecks and single points of failure. UUIDs eliminate coordination - each service generates IDs independently, no conflicts when merging data. For multi-tenant SaaS: customer 1's order #100 and customer 2's order #100 would collide with simple auto-increment, but UUIDs naturally prevent cross-tenant collisions. Implementation: generate UUID client-side or in application layer before INSERT, not in database trigger (faster, works offline).
  • 💡 Store UUIDs as binary in databases for 50% space savings: Default string storage 'xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx' = 36 chars = 36 bytes. Binary storage = 16 bytes (56% smaller). MySQL: use BINARY(16) + UNHEX()/HEX() functions. PostgreSQL: native UUID type stores as binary automatically. MongoDB: BinData type. JavaScript: convert to Buffer before storing. Savings: 1 million records = 20MB saved per UUID column. Also faster comparisons (binary vs string). Only downside: harder to debug (binary values unreadable), so add computed column or view with hex representation for human readability.
  • 💡 Generate UUIDs client-side to reduce database load and enable offline functionality: Modern browsers (crypto.randomUUID()), Node.js (crypto), and mobile SDKs can generate UUIDs locally without server round-trip. Benefits: (1) Reduce database load (no ID generation queries). (2) Batch inserts faster (pre-generate all IDs, single INSERT with multiple rows). (3) Optimistic UI updates (show new record immediately with generated ID, sync later). (4) Offline-first apps (create records offline, sync when online, zero ID conflicts). (5) Better error handling (retry failed inserts with same UUID without duplicate risk). Generate UUID → create record locally → INSERT to database, not INSERT → get auto-increment ID → update local record.
  • 💡 Understand UUID randomness doesn't provide security for access tokens: While UUIDs are unguessable (infeasible to brute-force valid IDs), they're not cryptographically secure access tokens. UUID security relies on 122 bits of entropy, but doesn't have expiration, revocation, or permission scoping. For security tokens: use JWT (signed tokens with claims), random tokens (256+ bits) with database lookup for permissions, or UUIDs as identifiers WITH separate authentication/authorization. Don't rely solely on UUID secrecy for access control - use proper authentication + check permissions on every request. UUID prevents enumeration attacks, not unauthorized access.
  • 💡 Consider UUIDv7 for time-ordered UUIDs with better database performance: New UUIDv7 (RFC 9562, 2024) combines timestamp prefix with random suffix - best of both worlds. Benefits over v4: (1) Sortable by creation time (like v1) without leaking MAC address. (2) Sequential inserts reduce B-tree page splits (better database performance). (3) Still globally unique without coordination. (4) Compatible with existing UUID infrastructure. When available in your language/framework, prefer v7 for database primary keys. Until v7 is widely supported, v4 remains safe default choice. Check if your database/ORM supports v7 before using.

When to Use This Tool

  • Database Schema Design: Generate sample UUIDs for testing primary key columns during database schema design, create test data with realistic UUID formats for development databases, verify UUID storage format (string vs binary) in different database systems
  • API Development: Generate unique request IDs for distributed tracing and log correlation, create unguessable resource identifiers for public APIs (preventing enumeration attacks), test UUID parsing and validation in API request handlers
  • Distributed Systems: Generate IDs for records created across multiple servers or microservices without coordination, create unique event IDs for event sourcing or message queues, test offline-first applications that create records without network connectivity
  • Security & Privacy: Generate session tokens or temporary file names with no predictable pattern, create resource IDs safe to expose in URLs without revealing business metrics (user count, order volume), replace sequential IDs that leak information about system scale and usage
  • Development & Testing: Quickly generate test data IDs for unit tests or integration tests, create realistic sample data for demos or documentation, generate bulk UUIDs for database seeding scripts or load testing
  • File Management: Generate unique filenames for user uploads to prevent collisions and path traversal attacks, create temporary file names for processing queues or background jobs, name cached files or artifacts with collision-free identifiers

Related Tools

  • Try our Hash Generator to create deterministic identifiers from data (similar to UUIDv5 but with more hash options)
  • Use our Password Generator to create secure random strings for authentication (different from UUIDs' identifier purpose)
  • Check our Base64 Encoder to encode UUIDs for shorter representations in URLs (36 chars → ~22 chars)
  • Explore our Timestamp Converter to convert between Unix timestamps and dates (useful with UUIDv1 timestamps)

Quick Tips & Navigation