UUID Generator
Generate UUID/GUID in multiple versions and formats
550e8400-e29b-41d4-a716-446655440000
Generated UUIDs (1)
Bulk Generation
About UUIDs
What is UUID?
UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems.
- • 128-bit identifier
- • Globally unique
- • No central authority needed
- • Multiple versions available
Common Use Cases
- • Database primary keys
- • Session identifiers
- • File naming
- • API request tracking
- • Distributed systems
- • Transaction IDs
Version Differences
UUID v1
Based on timestamp and MAC address. Provides uniqueness but may reveal information about the generating system.
UUID v4
Randomly generated. Most commonly used version. Provides excellent uniqueness with no information leakage.
Online UUID / GUID Generator
Generate random UUIDs (Universally Unique Identifiers) instantly with our free tool. Whether you need a standard v4 UUID or a time-based v1 UUID, we support multiple versions and formats. UUIDs (also known as GUIDs) are essential for developers creating unique keys for database records, user sessions, or distributed systems. Our generator runs locally in your browser, ensuring your unique IDs are generated privately and securely.
Features
- Generate UUID v1 (timestamp-based) and v4 (random)
- Bulk generation support (up to 100 at once)
- Custom formatting (Hyphens, Uppercase, Braces)
- One-click copy and bulk download
- Cryptographically secure random number generation
How to Use
- 1Select the UUID version (v4 is recommended for most use cases).
- 2Choose your desired output format (e.g., Default, Uppercase).
- 3Set the quantity of UUIDs to generate.
- 4Click "Generate" and then copy or download your list.
Frequently Asked Questions
Complete UUID Generator Guide
UUID Generator is an essential unique identifier generation tool for developers. Supports generating UUID v1 (timestamp-based) and v4 (random) versions, provides multiple output formats (default, uppercase, no hyphens, braces, URN), supports bulk generation of up to 100 UUIDs. Whether for database primary keys, session identifiers, file naming, API request tracking, or distributed systems, you can quickly generate globally unique identifiers. The tool is completely free, uses cryptographically secure random number generation, all operations done locally in browser. Understanding how to use the UUID generator helps you correctly use unique identifiers in development, avoid ID conflicts, improve system reliability.
1如何使用 / How to Use
Step 1: Select UUID Version
Select the UUID version to generate. v4 (Random): Most common, completely randomly generated, does not leak any information, suitable for most scenarios. v1 (Timestamp): Based on timestamp and MAC address, can be sorted by time, but may leak generation time and location info. Recommend using v4 version unless special needs (like time sorting required).
Step 2: Choose Output Format
Choose UUID format based on use scenario. Default: Standard format with hyphens (550e8400-e29b-41d4-a716-446655440000). Uppercase: All letters uppercase. No Hyphens: Remove all hyphens, suitable for some databases. Braces: Wrapped in braces, suitable for some programming languages. URN: URN format (urn:uuid:...), suitable for XML and other scenarios.
Step 3: Set Generation Count
Enter the number of UUIDs to generate (1-100). Can manually enter number or click quick buttons (1, 5, 10, 25, 50, 100) for fast setup. Bulk generation suitable for data initialization, testing, or scenarios requiring many unique identifiers. Each time version, format, or count is changed, automatically regenerates.
Step 4: Generate and Copy
Click "Generate" button to create new UUID list. Each UUID can be copied individually (hover to show copy button). Click "Copy All" to copy all UUIDs at once (one per line). After copying, shows "Copied" prompt, automatically disappears after 2 seconds. Suitable for quickly getting multiple UUIDs for code or database.
Step 5: Download as File
Click "Download" button to save UUID list as text file. Filename format: uuids-v4-timestamp.txt. One UUID per line, convenient for importing to database or other systems. Suitable for scenarios requiring saving many UUIDs or offline use. Downloaded file can be opened with any text editor.
2实际应用场景 / Use Cases
1Database Primary Keys
Use UUID as database table primary key, avoid auto-increment ID issues. Advantages: Globally unique, no conflicts; distributed system friendly; does not leak record count; can be generated on client. Suitable for distributed databases, microservices architecture, scenarios requiring data merging. Note: UUID takes more space than integers, index performance slightly lower. Recommend using v4 version, no-hyphen format can save space.
2Session and Token Identifiers
Generate user session IDs, access tokens, refresh tokens, etc. UUID randomness and uniqueness make them hard to guess and forge, improving security. Suitable for web apps, API authentication, single sign-on systems. Use v4 version to ensure complete randomness, avoid leaking time info. Can store UUID in Cookie, LocalStorage, or database. Regularly rotate tokens to improve security.
3File and Resource Naming
Use UUID to name uploaded files, generated reports, temporary resources, etc., avoid filename conflicts. Suitable for file upload systems, cloud storage, content management systems. UUID ensures no conflicts even when multiple users upload same-named files simultaneously. Can keep original filename as metadata, use UUID as actual storage name. No-hyphen format more suitable for filenames.
4API Request Tracking
Generate unique request ID for each API request, used for log tracking, error troubleshooting, performance analysis. Pass UUID in request header, server records in logs. When issues occur, can quickly locate related logs via Request ID. Suitable for microservices architecture, distributed tracing systems. Use v4 version, default format is fine.
5Distributed System Coordination
Generate globally unique transaction IDs, message IDs, task IDs, etc. in distributed systems. No central coordinator needed, each node can independently generate UUIDs. Suitable for message queues, distributed transactions, task scheduling systems. UUID ensures no conflicts even during network partitions. v4 version is safest, v1 version can provide time ordering.
6Test Data Generation
Bulk generate UUIDs for test data, simulated users, performance testing, etc. Can quickly generate many unique identifiers without worrying about duplicates. Suitable for unit testing, integration testing, stress testing. Use bulk generation to create multiple UUIDs at once, download as file then import to test scripts or database. Ensure test environment uses same UUID format as production.
使用技巧与最佳实践 / Tips & Best Practices
Choose Appropriate Version
v4 is the most common version, completely random, does not leak any information, suitable for 99% of scenarios. v1 is timestamp-based, can be sorted by time, but leaks generation time and MAC address (potential privacy issues). If time sorting needed, consider using v1 or separately storing creation time in database. If highest security and privacy protection needed, use v4.
Format Selection Recommendations
Default format (with hyphens) is standard format, best compatibility, recommended. No-hyphen format can save 4 characters of space, suitable for storage-sensitive scenarios. Uppercase format suitable for systems or standards requiring uppercase. Braces format suitable for C#, .NET, and other languages. URN format suitable for XML, RDF, and other semantic web scenarios. Consider system compatibility and storage efficiency when choosing format.
UUID Uniqueness Guarantee
UUID v4 uses 122 random bits (6 bits for version and variant), theoretically can generate 2^122 different UUIDs. Collision probability extremely low (about 10^-18), can be considered unique in practice. Even generating 1 billion UUIDs per second, would take 85 years for 50% probability of one collision. Therefore can confidently use in production without worrying about conflicts.
Database Index Optimization
When UUID is primary key, index performance slightly lower than auto-increment integers. Optimization suggestions: 1) Use CHAR(36) or BINARY(16) for storage; 2) Consider using UUID v1 or ULID for better sorting performance; 3) For MySQL, use BINARY(16) and UUID_TO_BIN() function; 4) For PostgreSQL, use native UUID type; 5) Add additional timestamp field for sorting.
Security Considerations
This tool uses browser's crypto.getRandomValues() API to generate cryptographically secure random numbers, suitable for production. UUID v4 is completely random, cannot predict next value, suitable for security-sensitive scenarios. Do not use UUID v1 as security token, as it contains timestamp and MAC address, may be predictable. For extremely high security requirements, consider using dedicated key generation algorithms (like CSPRNG).
常见问题 / Frequently Asked Questions
技术说明 / Technical Details
This tool uses modern browser crypto API to generate UUIDs compliant with RFC 4122 standard. **Core Features**: 1. Supports UUID v1 (timestamp) and v4 (random) 2. Five output formats (default, uppercase, no hyphens, braces, URN) 3. Bulk generation (1-100) 4. One-click copy single or all UUIDs 5. Download as text file 6. Real-time generation and preview **Technical Implementation**: - v4 uses crypto.getRandomValues() to generate cryptographically secure random numbers - v1 uses timestamp + random clock sequence + random node ID (simplified implementation) - Complies with RFC 4122 standard - 128-bit identifier, standard format is 8-4-4-4-12 hexadecimal - Version and variant bits set according to standard **UUID Structure**: - Time low (32 bits) - Time mid (16 bits) - Time high and version (16 bits) - Clock sequence and variant (16 bits) - Node ID (48 bits) **Randomness Guarantee**: - Uses crypto.getRandomValues() API - Cryptographically secure pseudo-random number generator (CSPRNG) - 122 effective random bits (v4) - Collision probability about 10^-18 **Format Conversion**: - Default: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx - Uppercase: XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX - No hyphens: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx - Braces: {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} - URN: urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx **Privacy Protection**: All generation done locally in browser, no data sent to servers. Does not store any generated UUIDs. Fully protects your privacy. **Tech Stack**: Next.js + React + TypeScript + Web Crypto API, ensuring security and performance.
🔒 隐私保护承诺 / Privacy Protection
所有处理都在您的浏览器本地完成，数据不会上传到任何服务器。您的隐私和数据安全是我们的首要任务。
All processing is done locally in your browser. No data is uploaded to any server. Your privacy and data security are our top priorities.