UUID (Universally Unique Identifier) is a 128-bit identifier used to uniquely identify information. Format: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (36 characters with hyphens). UUIDs are designed to be unique across all systems without central coordination.

What is the difference between UUID v4 and UUID v7?

UUID v4 is random and does not reveal timing information. UUID v7 combines a Unix millisecond timestamp with random bits, so generated IDs sort naturally by creation time. Use v7 for database primary keys, logs, and events; use v4 when unpredictability matters more than ordering.

When should I use UUIDs?

Use UUIDs for: database primary keys (distributed systems), session IDs, file names, API request IDs, user identifiers, and any case needing unique identifiers across systems. They eliminate the need for centralized ID generation.

UUID Generator Online - UUID v4 and v7

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What is UUID v7?

UUID v7 is a new UUID standard (RFC 9562, published 2024) that combines timestamp with randomness. Unlike v4 (random), v7 IDs are sortable by time, making them ideal for databases and distributed systems.

v7 Advantages

Time-sortable (K-sortable)
Better for database indexing
Extractable timestamp
Newer standard (2024)

v4 Advantages

Fully random and unpredictable
Universal support
No timing information leaked
Established standard

What is UUID Generator Online?

A UUID (Universally Unique Identifier) is a 128-bit identifier standard defined in RFC 9562 that guarantees uniqueness across space and time without requiring a central coordination authority. UUID v7 (the 2024 standard) embeds a Unix millisecond timestamp in the first 48 bits, producing identifiers that are both unique and chronologically sortable. That is a significant advantage for database indexing. UUID v4 uses pure cryptographic randomness, producing IDs that reveal no timing information. Both versions have collision probabilities so low they can be treated as zero for all practical purposes.

How to Use

Choose the UUID version: v7 (time-ordered, recommended for most uses) or v4 (fully random).
Set how many UUIDs to generate in a single batch (1 to 100).
Click Generate to create the identifiers.
UUID v7 results display the embedded timestamp for each ID.
Copy individual UUIDs by clicking the copy icon, or copy all at once with the Copy All button.
Use the generated UUIDs as database primary keys, API request IDs, or distributed system identifiers.

Why Use This Tool?

UUID v7 is time-sortable, which is ideal for database primary keys and B-tree index efficiency

Extract the creation timestamp from any UUID v7 without external metadata storage

UUID v4 is fully random, so no timing information is exposed and it can be suitable for security tokens

Generate up to 100 UUIDs in one batch for bulk seeding or testing

Uses the browser crypto API for cryptographically strong random number generation

All generation happens locally, so no identifiers or timing data are sent to any server

Tips & Best Practices

Use UUID v7 for database keys because they insert in chronological order and maintain B-tree efficiency
The UUID v7 timestamp is milliseconds since the Unix epoch, stored in the first 48 bits
Use UUID v4 for security tokens and session IDs where you do not want any timing information visible
UUID v7 is now the recommended default per RFC 9562 (published 2024)
Both versions have astronomically low collision probability, so you can safely use them without duplicate checking
Store UUIDs as 36-character strings or as 16-byte binary depending on your database and performance needs

Frequently Asked Questions

What is UUID v7 and why should I use it?

UUID v7 (RFC 9562, published 2024) embeds a Unix millisecond timestamp in the first 48 bits, making IDs naturally sortable by creation time. This solves the database indexing problem with random UUID v4: v7 IDs inserted in chronological order maintain B-tree efficiency, reducing page splits and write amplification. They are ideal for logs, events, and time-series data.

How do I extract the timestamp from a UUID v7?

The first 12 hexadecimal characters (48 bits) of a UUID v7 contain the Unix timestamp in milliseconds. Parse those characters as a hexadecimal number and convert to a date. This generator displays the extracted timestamp automatically next to each v7 UUID for verification.

When should I use UUID v4 instead of UUID v7?

Use UUID v4 when you need fully unpredictable identifiers, such as security tokens, session IDs, or any scenario where revealing the creation time would be a privacy or security concern. Use UUID v7 for database keys, event IDs, and logs where chronological ordering and index efficiency matter. For most application primary keys, v7 is the better choice.

When should I NOT use UUIDs?

Avoid UUIDs when you need human-readable identifiers (use slugs or sequential numbers instead), when storage size is critical (UUIDs are 36 chars as text or 16 bytes as binary vs 4 bytes for a 32-bit integer), or when you need strictly sequential IDs for regulatory requirements. Also avoid client-generated UUIDs when you need the database to be the single source of truth for ID assignment.

Is my generated UUID data kept private?

Yes. All UUID generation runs entirely in your browser using the Web Crypto API and local JavaScript. No generated identifiers, timestamps, or usage patterns are sent to any server, API, or third-party service. Your UUIDs are created and exist only on your device.

Are the generated UUIDs cryptographically secure?

Yes. The generator uses the browser crypto.getRandomValues() API for all random bits, which provides cryptographically strong randomness suitable for security-sensitive applications. This is significantly more secure than Math.random(). However, UUIDs are designed as identifiers, not as encryption keys or passwords. Use a dedicated key derivation function for those purposes.

Real-world Examples

Using UUID v7 as a Database Primary Key

Replace auto-incrementing integer primary keys with UUID v7 to enable distributed inserts without coordination, while maintaining chronological sort order for efficient B-tree indexing.

Input

Version: v7, Count: 5

Output

0192a3b4-c5d6-7e8f-9a0b-c1d2e3f4a5b6 (2025-06-15T10:30:00.000Z)
0192a3b4-c5d6-7e90-1234-567890abcdef (2025-06-15T10:30:00.001Z)
...

Generating Session Tokens with UUID v4

Generate UUID v4 tokens for user sessions where unpredictability matters more than sort order. The random nature prevents attackers from guessing valid session IDs.