UUID Generator: Complete Guide to Generating and Using UUIDs
Learn what UUIDs are, when to use v4, v1, v7, or nil, and how to generate, validate, and export UUIDs with our free UUID Generator tool. Best practices and common pitfalls.
🔑 UUIDs: Unique Identifiers for Every Use Case
UUIDs (Universally Unique Identifiers), also known as GUIDs, are 128-bit values used to uniquely identify resources without central coordination. Whether you're generating IDs for database records, API request IDs, distributed systems, or file names, choosing the right UUID version and using a reliable generator matters.
Why Use UUIDs?
UUIDs solve the problem of generating unique identifiers across systems, services, and time. They help you:
🗄️Database & API IDs
- •Primary keys that don't require a central sequence
- •Request IDs for tracing and idempotency
- •Merge-friendly when combining data from multiple sources
🌐Distributed Systems
- •Generate IDs offline or in any service without coordination
- •No single point of failure for ID generation
- •Sortable options (v1, v7) for time-ordered indexes
UUID Versions Explained
Different UUID versions serve different needs. Here's when to use each:
v4Random (most common)
Version 4 UUIDs are randomly generated. Use them when you need maximum uniqueness with no ordering requirement. Best for: primary keys, API IDs, session IDs, file names.
Example: 550e8400-e29b-41d4-a716-446655440000
v1Time-based + node
Version 1 UUIDs encode timestamp and MAC address (or random node). They are time-ordered and unique per node. Use for: legacy systems, when you need chronological ordering.
v7Time-ordered (modern)
Version 7 (RFC draft) combines timestamp with random data. Sortable by creation time and good for indexes. Use for: new systems where you want time-ordered, unique IDs.
nilNil UUID
The nil UUID is all zeros: 00000000-0000-0000-0000-000000000000. Use for: placeholders, "no ID" sentinels, or testing.
Using the UUID Generator Tool
Our UUID Generator makes it easy to generate, validate, and export UUIDs. Step-by-step:
1Choose version
Select v4 (random), v1 (time-based), v7 (time-ordered), or nil. The tool generates one UUID per click; use the count control to generate multiple at once.
2Format & copy
Toggle hyphens, uppercase, and optional braces (e.g. {uuid}). Copy a single UUID or the whole list. Validate pasted UUIDs to check format and version.
3Batch & export
Generate many UUIDs at once, then export to TXT, CSV, or JSON. Use for seeding databases, test data, or bulk ID generation. Save or share your list via link.
Best Practices for UUIDs
Follow these practices to use UUIDs effectively:
📏Choose the right version
- ✓Default to v4 for most use cases (random, no ordering)
- ✓Use v7 when you want time-ordered IDs for better index performance
- ✓Use v1 only when you need legacy compatibility or timestamp ordering
🔤Storage & display
Store UUIDs as 16-byte binary or 36-character strings (with hyphens). Use lowercase in APIs and URLs unless a system requires uppercase. Hyphens are standard (8-4-4-4-12).
550e8400-e29b-41d4-a716-446655440000 (standard)
550e8400e29b41d4a716446655440000 (no hyphens)
{550e8400-e29b-41d4-a716-446655440000} (with braces)📦Database indexing
Insert order is random; use UUID as primary key as-is or consider ULID/v7 for better locality.
Time-ordered IDs improve B-tree insert performance and range queries.
Common Pitfalls & How to Avoid Them
Avoid these mistakes when working with UUIDs:
❌Wrong version digit
The version is encoded in the 13th character (first digit of the third group). v4 uses 4, v1 uses 1, v7 uses 7. Mismatched version can break validation or ordering assumptions.
⚠️Case sensitivity
UUIDs are case-insensitive per RFC, but stay consistent: use lowercase in URLs and JSON for readability. Some databases or APIs expect a specific case.
🔢Not validating on input
Always validate UUIDs from user input or external systems. Use the tool's validate feature or a regex/validator in your code to reject malformed IDs before storing or querying.
🔄Mixing versions
Don't mix v4 and v7 in the same table if you rely on time ordering. Pick one strategy per entity type and stick with it.
Pro Tips for Power Users
Get more from the UUID Generator:
🔍Validate before import
Paste a list of UUIDs (one per line or comma-separated) and use the validator to ensure all are valid and to detect version. Fix duplicates or malformed IDs before importing into a database.
📤Export for your stack
Export to JSON array for API payloads, CSV for spreadsheets or bulk insert, or plain TXT for scripts. Use the same format (hyphens, case) as your application.
💾Save & share
Save your generated list with a name for quick access, or share via link so teammates can open the same set of UUIDs. All generation runs in the browser—nothing is sent to a server.
✅ Ready to Generate UUIDs?
Use our UUID Generator tool to create v4, v1, v7, or nil UUIDs, validate existing IDs, and export to TXT, CSV, or JSON. Free, no sign-up, and 100% client-side.
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