UUID Guide for Developers
Complete guide to UUID versions, use cases, and best practices in software development.
← Back to Developer Tools
UUID Generator Online
Generate v1, v3, v4, v5, v6, v7 UUIDs · Bulk export · Validate · Inspect · Batch check
Configuration
UUID Version
🎲 Cryptographically random — most common choice
Format Options
Export As
Ctrl + Enter to generate
Output
🔑
Click "Generate UUID" or press Ctrl+Enter
Frequently Asked Questions
What is a UUID and what does it stand for?
UUID stands for Universally Unique Identifier — a 128-bit label standardised in RFC 4122 (updated as RFC 9562). It is represented as 32 hexadecimal characters in 5 groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs are designed to be unique without requiring a central coordinator, making them ideal for distributed systems, databases, and APIs.
Which UUID version should I use?
For most applications, use v4 (random) — it is the simplest and most common choice with excellent uniqueness guarantees. Use v7 for database primary keys as it is time-ordered and indexes efficiently. Use v1 or v6 when you need to recover the generation time from the UUID itself. Use v3 or v5 when you need deterministic UUIDs from the same namespace + name input — useful for consistent resource identifiers.
What is the difference between UUID v4 and v7?
UUID v4 is entirely random with no embedded information — it is the safest choice when you do not need ordering. UUID v7 embeds the current Unix millisecond timestamp in the first 48 bits, making it lexicographically sortable. This makes v7 far more efficient for database primary keys because it generates index-friendly sequences — new UUIDs always sort after existing ones, reducing B-tree fragmentation by up to 90%.
Can two UUIDs ever be the same?
Theoretically yes, but practically the probability is negligible. UUID v4 has 2¹²² ≈ 5.3 × 10³⁶ possible values. To have a 50% chance of a collision, you would need to generate approximately 2.7 × 10¹⁸ UUIDs — far beyond any real-world system. The collision probability panel in this tool shows the exact mathematical probability using the Birthday Problem formula.
What is a namespace UUID (v3 and v5)?
Namespace UUIDs (v3 and v5) are deterministic — the same namespace + name input always produces the same UUID output. v3 uses MD5 hashing and v5 uses SHA-1. Standard namespaces include DNS (for domain names), URL, OID, and X.500 DNs. They are useful when you want the same resource (e.g., a URL or email address) to always map to the same UUID, enabling idempotent systems.
What is the difference between UUID and GUID?
GUID (Globally Unique Identifier) is Microsoft's implementation of UUID, used in Windows COM and .NET. They are functionally the same 128-bit standard but GUIDs are often displayed in uppercase with curly braces: {550E8400-E29B-41D4-A716-446655440000}. This UUID generator supports both formats — use the Braces format option for GUID-style output.
Related Blog Articles
You might also like
Related Tools
Popular
HTML Formatter
Beautify, validate & preview HTML. Accessibility audit, SEO check, HTML→JSX/React/Vue.
Popular
SQL Formatter
Format, minify & validate SQL. Auto-detect dialect, AI explain & optimize, code snippet generator.
New
Lorem Ipsum Generator
Generate placeholder text. Paragraphs, sentences, words or bytes. HTML, Markdown, JSON output.
New
Slug Generator
Generate SEO-friendly URL slugs. Stop word removal, SEO score, bulk mode, AI suggestions.
Popular
.gitignore Generator
Generate .gitignore files for 50+ stacks — Node, Python, React, Go, Docker and more.
Explore Other Tools
🎨 Media
Image to PDF
Convert JPG, PNG, WebP to PDF. Drag to reorder, A4/Letter/Fit page size, margin control. Up to 50 images.
🌾 Farming
Irrigation Cost Calculator
12 Gujarat crops ET data. Drip/sprinkler/flood, electric/diesel/solar pump. DGVCL/UGVCL rates, GGRC 55% subsidy, solar payback, monthly calendar, cost per quintal.
🏥 Health
BMI Calculator
BMI with Asian cutoffs, 4 ideal weight formulas, health score, body composition & weight timeline.