Which UUID version should I use?

V4 (Random) is the standard choice for most use cases — it's random, simple, and widely supported. Use V7 (Sortable) for database primary keys where insertion order matters. Use V1 (Timestamp) when you need to extract creation time from the ID. Use V3/V5 when you need deterministic IDs from a namespace + name combination.

What's the difference between V3 and V5?

Both generate deterministic UUIDs from a namespace and name. V3 uses MD5 hashing, while V5 uses SHA-1. V5 is preferred because SHA-1 provides better uniqueness guarantees. Same namespace + name always produces the same UUID for a given version.

What is UUID V7 and why use it for databases?

UUID V7 embeds a millisecond-precision Unix timestamp, making values naturally sorted by creation time. This improves B-tree index performance (fewer page splits), better cache utilization, and efficient range queries. It's ideal for database primary keys in high-volume applications.

NanoID is a compact alternative to UUID — 21 characters vs 36, URL-safe (A-Z, a-z, 0-9, _, -), and faster to generate. Perfect for short URLs, compact database keys, and scenarios where readability and size matter.

ULID (Universally Unique Lexicographically Sortable Identifier) is a 26-character identifier combining timestamp + randomness. Unlike UUIDs, ULIDs sort chronologically as strings, making them excellent for database indexes and distributed systems where ordering matters.

What does the UUID Decoder do?

Paste any UUID to instantly see its version number, variant type (RFC 4122, Microsoft, etc.), embedded timestamp (for V1 and V7), and raw hexadecimal value. It accepts UUIDs with or without hyphens, braces, and quotes.

Are these IDs truly unique?

For practical purposes, yes. UUID V4 has 2^122 possible combinations. Collision probability is astronomically low — you'd need to generate 2.7 quintillion UUIDs for a 50% chance of one collision. V3/V5 are deterministic (same input = same output), while V1/V7 combine time + randomness.

Yes. All IDs are generated in your browser using the Web Crypto API (crypto.getRandomValues). No data is sent to any server. V3/V5 use standard MD5/SHA-1 hashing for deterministic generation, while V1/V4/V7 use cryptographically secure random numbers.

Tools

Quantity

UUID Version

Format

Letter Case

Hyphens

Wrap

Generated

Click "Generate" to create UUIDs

UUID Validator & Version Detector

UUID / GUID Generator

Generate UUIDs, GUIDs, NanoIDs, and ULIDs online instantly. Create v1 (time-based), v3/v5 (name-based), v4 (random), v6, or v7 (sortable time-ordered) UUIDs with one click. Bulk generate thousands of unique IDs for database seeding and testing. Validate and decode UUIDs to inspect version, variant, and timestamp. Customize output case, hyphens, and braces wrapping. Copy to clipboard or download as text file. All generation uses cryptographically secure random numbers — no data leaves your browser.

Features

✓Multiple UUID versions — generate V1 (timestamp), V3 (MD5 name-based), V4 (random), V5 (SHA-1 name-based), V7 (sortable)
✓Multiple ID formats — UUID, NanoID, and ULID generation in one tool
✓Format options — uppercase, no hyphens, braces {}, quotes "" for UUID output
✓UUID Decoder — paste any UUID to inspect its version, variant, and timestamp
✓Bulk generation — create up to 1,000 IDs at once for testing and database seeding
✓V3/V5 namespace support — DNS, URL, OID, X500 predefined namespaces
✓One-click copy — copy individual IDs or all results to clipboard instantly
✓Download as file — export generated IDs as a .txt file
✓Cryptographically secure — uses browser's crypto API for maximum security
✓Entirely client-side — all generation happens in your browser, zero data uploaded

How to Use

1Select the UUID version tab (V1, V3, V4, V5, V7) or switch to NanoID/ULID mode.
2For V3/V5: choose a namespace (DNS, URL, OID, X500) and enter a name — same inputs always produce the same UUID.
3Use format checkboxes (Uppercase, No hyphens, Braces, Quotes) to customize UUID output format.
4Set the quantity (1–1,000) and results update automatically.
5Click Copy to copy a single ID, or Copy All / Download for bulk results.
6Expand the UUID Decoder section to inspect any UUID's version, variant, and embedded timestamp.

Frequently Asked Questions

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