A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. Also known as GUID (Globally Unique Identifier). The standard format is xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

What is the difference between UUID v1, v4, and v7?

UUID v1 uses timestamp + MAC address (sequential but reveals info). UUID v4 is purely random (most common, no ordering). UUID v7 is timestamp-based and sortable (newest standard, best for databases).

UUID Generator — Free Online UUID/GUID Generator (v1, v4, v7)

Click the UUID to copy • Press Space or Enter to regenerate

UUID v4

Random — most common

⭐ Most Popular

UUID v1

Timestamp-based

📅 Sequential

UUID v7

Timestamp + random, sortable

🆕 RFC 9562

Format:

Bulk count:

Generated UUIDs

🔍 UUID Parser & Validator

What is a UUID?

A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit number used to uniquely identify resources in distributed systems without a central authority. The standard representation is 32 hexadecimal digits in 5 groups separated by hyphens: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

UUID Versions Compared

Version	Method	Sortable	Privacy	Use Case
v1	Timestamp + MAC	Partial	⚠️ Leaks MAC	Legacy systems
v4	Random	No	✅ Private	General purpose
v7	Timestamp + Random	✅ Yes	✅ Private	Databases, modern apps

Why Use UUID v7?

UUID v7 (defined in RFC 9562) is the newest and most recommended version for new projects. It embeds a Unix timestamp in the first 48 bits, making UUIDs naturally sortable by creation time — perfect for database primary keys where index performance matters.

UUID Format

128 bits = 16 bytes = 32 hex characters
The M nibble indicates the version (1, 4, or 7)
The N nibble indicates the variant (8, 9, a, or b for RFC 4122)
Total possible v4 UUIDs: 2¹²² ≈ 5.3 × 10³⁶

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