What is the difference between UUID v4 and UUID v7?

UUID v4 is entirely random — 122 bits of random data — making it unpredictable and globally unique but not sortable. UUID v7 (RFC 9562) uses 48 bits for a Unix millisecond timestamp followed by 74 bits of random data. The timestamp prefix means v7 UUIDs generated later always sort after those generated earlier, which dramatically improves B-tree database index insert performance. OWASP recommends UUID v7 over v4 for database primary keys in new projects.

When should I choose ULID over UUID v7?

Both ULID and UUID v7 are time-sorted, so the primary differences are format and ecosystem support. ULID uses 26 Crockford Base32 characters (no hyphens, case-insensitive, URL-safe) vs UUID's 36-character hyphenated hex. ULID is more human-readable in URLs and logs. UUID v7 uses the standard UUID format, offering better compatibility with existing UUID-aware libraries, databases, and ORMs. Choose ULID for new systems where string aesthetics matter; choose UUID v7 for maximum ecosystem compatibility.

Can I extract a timestamp from a UUID v7 or ULID?

Yes. UUID v7's first 48 bits encode the Unix epoch in milliseconds — extract bits 0–47, interpret as a 64-bit integer, and convert to a datetime. ULID encodes the same 48-bit millisecond timestamp in the first 10 Crockford Base32 characters. The Parse tab in this tool does this extraction automatically, displaying the embedded timestamp in ISO 8601 format. This makes v7/ULID identifiers useful for debugging and auditing without a separate `created_at` column.

OmniToolsKit

UUID & ULID Generator

Name: UUID & ULID Generator
Rating: 5 (2 reviews)
Author: OmniToolsKit

Generate universally unique identifiers (UUID) and universally unique lexicographically sortable identifiers (ULID).

RFC 4122 CompliantBulk GenerationOne-click CopyCollision-free IDs

UUID Configuration

Generate standard UUIDs (Versions 1, 3, 4, 5)

Version

Quantity

About this tool

Generate, parse, and validate UUIDs (v1, v4, v7) and ULIDs directly in your browser. This UUID and ULID generator covers the full spectrum from universally unique identifiers to lexicographically sortable IDs — essential for database primary keys, distributed systems, and event sourcing architectures.

About

UUID v4, v7 and ULID Generator, Parser, and Validator

Unique identifiers are fundamental to distributed systems, database design, event-driven architecture, and API resource naming. The choice of identifier format affects database indexing performance, URL design, chronological ordering, and debuggability — making the right selection important for system architecture.

This tool covers three modern identifier standards: UUID v4 (randomly generated, the most widely used format), UUID v7 (timestamp-based with monotonic ordering, the new RFC 9562 recommendation for database primary keys), and ULID (Universally Unique Lexicographically Sortable Identifier, designed as a sortable UUID alternative). UUID v1 is also supported for legacy compatibility and timestamp extraction.

All generation uses the Web Crypto API for cryptographically secure randomness. The parser and validator accept any UUID or ULID string and return structured metadata — version, variant, embedded timestamp (for v1/v7/ULID), and validity status. No identifiers are transmitted to any server.

What makes it unique

UUID v7 and ULID — Why Sortability Matters for Databases

UUID v4's random structure causes B-tree index fragmentation in databases — inserts scatter across the index, degrading write performance at scale. UUID v7 and ULID solve this by embedding a millisecond-precision timestamp as the most significant bits, ensuring new identifiers sort after existing ones. This sequential ordering dramatically improves B-tree insert performance in PostgreSQL, MySQL, and SQLite. ULID uses Crockford's Base32 encoding (26 characters vs UUID's 36) and is case-insensitive and URL-safe. UUID v7 uses standard UUID format for maximum library compatibility.

Common Use Cases for UUID and ULID Generator

Database Primary Key Generation

Generate UUID v7 or ULID values for database primary keys to achieve globally unique, time-ordered IDs that insert efficiently into B-tree indexes without fragmentation.

API Resource Identifier Design

Use UUID v4 for externally exposed API resource identifiers where unpredictability is required, preventing resource enumeration attacks via sequential IDs.

Distributed Event Stream Identifiers

Generate ULID or UUID v7 identifiers for events in distributed systems where chronological ordering of IDs enables efficient time-range queries and stream replay.

How to Use

1
Select an Identifier Type
Choose UUID v4 (random, widely compatible), UUID v7 (time-ordered, recommended for new database schemas), ULID (sortable, compact Base32 format), or UUID v1 (time-based, legacy MAC address-based format).
2
Generate One or Multiple Identifiers
Click Generate to produce a single identifier, or use the bulk generation option to create 10, 100, or 1000 identifiers at once for seeding databases, populating test fixtures, or initializing event streams.
3
Parse or Validate an Existing Identifier
Paste any UUID or ULID string into the Parse tab to extract its embedded metadata — for UUID v7 and ULID, the embedded timestamp is extracted and displayed in human-readable ISO 8601 format along with the random component.

Features

UUID v7 Time-Ordered Generation
Generates RFC 9562 UUID v7 identifiers with millisecond-precision timestamp prefix, ensuring lexicographic ordering matches chronological insertion order for B-tree index efficiency.
ULID Generation and Parsing
Produces 26-character Crockford Base32 ULIDs with embedded 48-bit millisecond timestamp. Parses existing ULIDs to extract creation timestamp and random component.
UUID Format Validation and Metadata Extraction
Validates any UUID string against RFC 4122/RFC 9562 format rules and extracts version, variant, and timestamp data from v1 and v7 identifiers.

Frequently Asked Questions

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