UUID v4 vs UUID v7 — which should you use?
UUID v4 is the default for most use cases — fully random 128-bit identifier, essentially zero collision risk. UUID v7 (2024) adds time-ordering: the first 48 bits are a millisecond-precision Unix timestamp.
| UUID v4 | UUID v7 | |
|---|---|---|
| Entropy | 122 bits random | 74 bits random + 48 bits timestamp |
| Sortable by creation time | No (random) | Yes |
| Database B-tree insert performance | Poor (random inserts fragment the index) | Excellent (append-only behavior) |
| Leaks info | None | Creation timestamp |
| Use for DB primary keys | OK on small tables | Preferred on large tables |
| Use for session tokens / secrets | Yes — no info leak | No — leaks timing |
Rule of thumb: use v7 for database primary keys and IDs you'll sort by time; use v4 for anything user-facing or secret-adjacent (session tokens, API request IDs, reset tokens).
Generate a UUID in every major language
Native or standard-library UUID generators in common dev languages:
// JavaScript / TypeScript (browser + Node 14.17+)
crypto.randomUUID()
// "f47ac10b-58cc-4372-a567-0e02b2c3d479"
# Python 3
import uuid
str(uuid.uuid4())
# UUID v7 needs `uuid-utils` or `uuid7` library
// Java
java.util.UUID.randomUUID().toString();
// C# / .NET
System.Guid.NewGuid().ToString();
// Go
import "github.com/google/uuid"
uuid.NewString() // v4
uuid.NewV7().String() // requires google/uuid v1.6+
// Rust
use uuid::Uuid;
Uuid::new_v4().to_string();
// Kotlin
java.util.UUID.randomUUID().toString()
// Swift
UUID().uuidString
All of these use cryptographically secure random generators (/dev/urandom or OS CSPRNG) — no need to worry about predictability. The odds of two UUID v4s colliding across a billion calls is roughly 1 in 1018.
UUID in Minecraft — player lookup explained
Minecraft assigns every player a UUID derived from their Microsoft/Mojang account. The UUID persists even if the player changes their display name — servers use it for bans, permissions, and inventory storage.
Format in Minecraft:
- Trimmed:
069a79f444e94726a5befca90e38aaf5(no hyphens, lowercase). This is the format stored in NBT files. - Dashed:
069a79f4-44e9-4726-a5be-fca90e38aaf5(with hyphens). Used in JSON APIs and URLs.
Lookup APIs:
# Player name → UUID
curl https://api.mojang.com/users/profiles/minecraft/<playername>
# → {"id":"069a79f444e94726a5befca90e38aaf5","name":"Notch"}
# UUID → name history
curl https://sessionserver.mojang.com/session/minecraft/profile/<uuid>Minecraft UUIDs are valid RFC 4122 UUID v3 (name-based, MD5-hashed) — generated from the account's username at creation time.
Frequently Asked Questions
How do I generate a UUID (or GUID) online?
Click Generate and the tool produces a cryptographically-random UUID v4 (for example, `f47ac10b-58cc-4372-a567-0e02b2c3d479`). Use Bulk Generate to create 10, 100 or 1000 UUIDs at once — perfect for seeding test data.
What's the difference between UUID v4, v1 and v7?
UUID v4 is fully random (most common). UUID v1 encodes timestamp + MAC address (leaks host info). UUID v7 is time-ordered (sortable by creation time, better for database primary keys). Our generator supports v1, v4 and v7 — pick by use case.
Is a GUID the same as a UUID?
Yes. GUID (Globally Unique Identifier) is Microsoft's name for UUID (Universally Unique Identifier). They're the same 128-bit format, same generation algorithm — the terms are interchangeable across Windows, .NET, Java, Python and JavaScript.
Are the UUIDs generated here unique and safe for production?
Yes. UUID v4 uses `crypto.getRandomValues()` from the Web Crypto API — cryptographically strong randomness. The chance of collision in a billion UUIDs is roughly 1 in 10^18. Safe for database primary keys, session IDs, API request IDs.
How do I generate a UUID v4 in JavaScript, Python or C#?
JavaScript: `crypto.randomUUID()`. Python: `uuid.uuid4()`. C#: `Guid.NewGuid()`. Go: `uuid.NewRandom()`. Our tool uses the same `crypto.randomUUID()` under the hood — it's a reference implementation in the browser.
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