Free UUID Generator Online — Generate v1, v4, v5, v7 UUIDs Instantly

Quick Start

How to Generate UUIDs

From zero to a perfectly formatted UUID batch in three clicks

1

Choose a UUID Version

Select the UUID version that fits your use case: v4 for general-purpose random IDs (most common), v7 for database primary keys that sort chronologically, v5 for deterministic content-addressed IDs, or v1 for time-stamped identifiers.

💡 When in doubt, use v4. It's the most widely supported, most private, and works correctly in every context.

2

Set Count & Format

Enter how many UUIDs to generate (1 to 1000) and pick your output format: lowercase (standard), UPPERCASE, {braces} for .NET/COM, no-hyphens for compact hex, or urn: prefix for URN systems.

💡 For v5, also enter a namespace (or pick a standard namespace like DNS/URL) and a name string — the same inputs always produce the same UUID.

3

Generate, Copy & Use

Click Generate to produce your UUIDs instantly. Copy individual UUIDs with a single click, copy all at once, or download the full batch as a .txt file for use in SQL scripts, seed files, or test fixtures.

💡 Use the Download button to get a newline-delimited file — perfect for feeding into scripts with xargs, awk, or sed.

Version Guide

UUID v1 vs v4 vs v5 vs v7 — Which Should You Use?

Each version has a distinct algorithm and specific use cases. Choose based on your requirements.

Most PopularRFC 4122 §4.4

122 bits of cryptographic randomness. No time or namespace component. The safest choice for most applications.

Algorithm

crypto.randomUUID() / crypto.getRandomValues()

Example UUID

550e8400-e29b-41d4-a716-446655440000

Pros

Maximum entropy
No MAC address leak
Best privacy
Universal default

Cons

✕Not time-sortable
✕Not deterministic

Best Use Cases

Database primary keysSession tokensAPI request IDsFile namesGeneral-purpose IDs

Output Formats

5 UUID Output Formats

Switch formats without regenerating — same UUID, different presentation

LowercaseDefault

The RFC 4122 canonical format. Hex characters a-f in lowercase, five groups separated by hyphens.

550e8400-e29b-41d4-a716-446655440000

Use: APIs, databases, URLs, JSON payloads — the universal default

UPPERCASE

All hex characters in uppercase. Some legacy systems and Windows APIs expect this format.

550E8400-E29B-41D4-A716-446655440000

Use: Windows APIs, .NET GUID format (without braces), legacy enterprise systems

{Braces}

UUID wrapped in curly braces — the Microsoft GUID/COM format used by Windows Registry, COM/DCOM, and .NET.

{550e8400-e29b-41d4-a716-446655440000}

Use: .NET Guid.ToString('B'), Windows Registry keys, COM/OLE identifiers

No Hyphens

32-character compact hex string with no hyphens. Shorter and URL-safe.

550e8400e29b41d4a716446655440000

Use: Short URL slugs, compact storage, hex ID fields, hash-like identifiers

URN Format

UUID as a Uniform Resource Name per RFC 4122 §3. Used in XML namespaces and URN-based identifier systems.

urn:uuid:550e8400-e29b-41d4-a716-446655440000

Use: XML namespaces, LDAP attributes, URN-based resource systems, SAML

Features

Everything in One UUID Tool

All UUID versions, formats, and generation options in one free browser tool

UUID v4 — Cryptographically Random

Generate RFC 4122 compliant UUID v4 identifiers using the browser's crypto.randomUUID() API. The gold standard for IDs — 122 bits of entropy, effectively zero collision probability.

UUID v1 — Time-Based

Generate UUID v1 identifiers derived from the current timestamp and a random node value. Monotonically increasing within the same millisecond — useful for time-ordered logs.

UUID v5 — Namespace + Name (SHA-1)

Generate deterministic UUID v5 by hashing a namespace UUID and a name string with SHA-1. The same namespace + name always produces the same UUID — ideal for stable content-addressed IDs.

UUID v7 — Timestamp-Sortable

Generate UUID v7 identifiers with a 48-bit Unix millisecond timestamp prefix. Lexicographically sortable, making them ideal for database primary keys with natural chronological ordering.

Bulk Generation (1–1000)

Generate up to 1000 UUIDs in a single operation. Copy all at once or download as a .txt file. Perfect for seeding databases, creating test fixtures, or batch ID allocation.

5 Output Formats

Format UUIDs as lowercase (RFC canonical), UPPERCASE, {braces} (GUID/COM style), no-hyphens (compact hex), or urn:uuid: prefix. Switch format without regenerating.

Copy & Download

Copy any single UUID or all generated UUIDs to clipboard with one click. Download the full batch as a newline-delimited .txt file for use in scripts and fixtures.

100% Private — Runs in Browser

All UUID generation uses browser-native APIs (crypto.getRandomValues, crypto.randomUUID). No server calls, no logging, no data transmission. Safe for sensitive ID generation.

Use Cases

When and Why to Use UUIDs

Practical scenarios where UUID generation is the right solution

Database

Database Primary Keys

UUIDs as primary keys eliminate auto-increment collisions in distributed databases. Use v7 for B-tree index efficiency (natural sort order reduces page splits) or v4 for maximum privacy.

INSERT INTO users (id, name) VALUES ('550e8400-e29b-41d4-a716-446655440000', 'Alice')

API Development

API Request Tracing

Assign a UUID to every API request as a correlation ID. Log it at every service boundary so you can trace a single request through distributed logs using a simple grep.

X-Request-ID: 7f9c2a4e-3b8d-4f1e-9c2a-6b7d8e9f0a1b

API Security

Idempotency Keys

Generate a UUID client-side and send it as an idempotency key with payment or mutation requests. The server uses it to detect and deduplicate retried requests without double-processing.

Idempotency-Key: a1b2c3d4-e5f6-4a7b-8c9d-0e1f2a3b4c5d

Storage

File & Asset Naming

Name uploaded files with UUIDs to prevent collisions, bypass path traversal attacks, and avoid exposing original filenames. The UUID becomes the canonical reference in your database.

uploads/550e8400-e29b-41d4-a716-446655440000.jpg

Security

Session & Token IDs

Generate v4 UUIDs as session IDs or CSRF tokens. Their 122 bits of entropy make brute-force guessing statistically impossible — far more secure than sequential integers.

Set-Cookie: session_id=7a2f...; HttpOnly; Secure

Testing

Test Data & Seed Fixtures

Bulk generate 100, 500, or 1000 UUIDs for test fixtures, database seeds, or mock data. Download as a .txt file and pipe into SQL scripts or JSON fixtures with a shell one-liner.

cat uuids.txt | xargs -I{} echo "INSERT INTO items (id) VALUES ('{}');"

Deep Dive

The Developer's Complete Guide to UUIDs

What Is a UUID — The 128-Bit Identity Standard

A UUID (Universally Unique Identifier) is a 128-bit value standardized in RFC 4122 (and its 2024 successor RFC 9562) for identifying information without a central authority. Its canonical string form — 32 hex characters in the pattern 8-4-4-4-12 like 550e8400-e29b-41d4-a716-446655440000 — is recognized by every major programming language, database, and framework. The 'universally unique' property means any two independently generated UUIDs are guaranteed to be different with overwhelming statistical probability, without requiring a database sequence, a central ID service, or coordination between nodes. This makes UUIDs the foundation of distributed systems design: any service, device, or client can create globally unique identifiers independently.

UUID v4 vs v7 — Which Should You Use for Database Keys?

UUID v4 has been the default for a decade — generate a random 122-bit ID and you're done. The problem emerged at scale: random UUIDs insert into B-tree indexes at arbitrary positions, causing frequent page splits and cache thrashing. Benchmarks show UUID v4 primary keys can be 20-40% slower than auto-increment at high insert volumes on large tables. UUID v7, standardized in RFC 9562 (April 2024), solves this by prefixing the UUID with a 48-bit Unix millisecond timestamp. Since new rows always have larger timestamps than existing ones, inserts cluster at the end of the index — the same access pattern as auto-increment. The result: UUID v7 achieves insert performance comparable to sequential integers while retaining all UUID advantages. For any new project using PostgreSQL, MySQL 8+, or MariaDB with a high-volume insert workload, UUID v7 is now the recommended choice for primary keys.

UUID v5 — Deterministic IDs for Content-Addressed Systems

UUID v5 is the underappreciated power tool of the UUID family. Instead of random bytes, v5 takes a namespace UUID and a name string, hashes them with SHA-1, and maps the result to a UUID. The crucial property: the same namespace + name always produces the same UUID. This enables content-addressed identity — deriving stable IDs from the content itself. Practical applications: URL canonicalization where two different URL strings for the same resource always resolve to the same UUID ID; configuration-driven resources where the ID is derived from a slug or key rather than a database sequence; idempotent API design where clients can safely retry resource creation using the predictable ID; database deduplication where you can detect and merge duplicate records by comparing their v5 UUIDs before inserting. The standard namespaces (DNS, URL, OID, X500) from RFC 4122 ensure namespace isolation between different identity domains.

UUID Security — When Random IDs Protect Your Data

The security implications of UUID choice are subtle but important. Auto-increment integer IDs (/api/orders/10042) are enumerable — any user can iterate through all records by incrementing the ID. This is called an IDOR (Insecure Direct Object Reference) vulnerability and is consistently in the OWASP Top 10. UUID v4 IDs are opaque and non-enumerable — guessing a valid UUID by brute force requires trying 2^122 possibilities. For user-accessible resources (profile pages, file downloads, order details), UUIDs provide fundamental access control defense-in-depth. UUID v7 IDs reveal creation timestamp — consider this when the timing of resource creation is sensitive. UUID v1 in its original specification embeds the MAC address of the generating machine — this leaks infrastructure details and is why v1 is deprecated in favor of v4 and v7 for public-facing identifiers.

UUID in Distributed Systems and Microservices

UUIDs are foundational infrastructure in distributed systems. In a microservices architecture, multiple services need to create and reference shared entities without centralizing the ID generation — a central sequence is a single point of failure and a coordination bottleneck. UUIDs allow any service to generate IDs independently. Correlation IDs — a UUID attached to every inbound request and propagated through all service calls — enable distributed tracing: when an error occurs at any layer, grep for the correlation ID across all service logs to reconstruct the exact request path. Idempotency keys — UUID v4 generated client-side for payment or mutation requests — allow clients to safely retry failed requests without double-processing. Event sourcing architectures use UUIDs as aggregate IDs and event IDs, ensuring stable identity across event replay and projection rebuilds. These patterns collectively explain why UUID generation is one of the most common operations in modern backend services.

How to Store UUIDs Efficiently

Storage efficiency matters at scale. A UUID stored as a VARCHAR(36) or CHAR(36) string uses 36 bytes. The same UUID stored as a BINARY(16) or native UUID type uses 16 bytes — less than half the space. At 100 million rows, that's 2GB vs 1.6GB just for the primary key column, before considering index copies. PostgreSQL has a native uuid type (16 bytes, indexed as binary, accepts all string input formats). MySQL 8.0+ has UUID_TO_BIN() and BIN_TO_UUID() functions for converting between string and 16-byte binary representation. MySQL also supports a 'swap_flag' parameter that reorders the time component of v1 UUIDs to improve index locality. SQL Server has the uniqueidentifier type (16 bytes). SQLite has no native UUID type — use TEXT or BLOB(16). For most applications, use the native UUID type when available. For MySQL workloads with high insert throughput, BINARY(16) with UUID v7 gives the best performance.

Best Practices

UUID Best Practices

Recommendations for using UUIDs correctly in production systems

High Priority

Use UUID v7 for New Database Primary Keys

UUID v7's timestamp prefix gives you sequential insert performance (like auto-increment) with all UUID benefits. Adopt it in new tables before you hit scale — retrofitting an existing table's primary key type is painful.

High Priority

Use Native UUID Types, Not VARCHAR

Store UUIDs in the database's native UUID or BINARY(16) type. PostgreSQL uuid, MySQL BINARY(16) with UUID_TO_BIN, and SQL Server uniqueidentifier all halve storage vs VARCHAR(36) and improve index performance.

Recommended

Add Correlation IDs to Every API Request

Generate a UUID v4 server-side for every inbound request and log it at every service boundary. This single practice reduces debugging time for production incidents by hours.

High Priority

Never Use Math.random() for IDs

Math.random() is a deterministic PRNG — it is not cryptographically secure and should never be used for IDs, tokens, or keys. Always use crypto.randomUUID() or crypto.getRandomValues() in browsers/Node.js.

Recommended

Use UUID v5 for Content-Addressed Resources

If you need stable, reproducible IDs derived from data (URLs, document titles, config keys), UUID v5 with a consistent namespace eliminates the need for a lookup table to maintain the name→ID mapping.

Reviews

What Developers Say

“The v7 UUID generator saved us from a painful migration. We started using it for new tables before switching our entire schema — sequential insert performance is night and day compared to v4.”

Sven Larsson

Backend Engineer

SaaS Platform Team

“I use the v5 UUID feature constantly for content-addressed IDs. Same URL always gives the same UUID — no lookup table needed. The namespace selector makes it easy to use the standard DNS/URL namespaces.”

Priya Nair

Software Architect

Distributed Systems Consultancy

“Bulk generate 500 UUIDs, download as .txt, pipe into a SQL seed script. The entire test data setup for a sprint takes 30 seconds instead of writing a Python script every time.”

Jake Morrison

Full-Stack Developer

Startup Engineering

“Finally a UUID tool that explains the versions properly. I didn't understand when to use v5 until reading this page — the deterministic content-addressing use case was exactly what I needed for our URL canonicalization system.”

Chen Wei

Senior Developer

E-Commerce Platform

FAQ

Frequently Asked Questions

Everything developers ask about UUIDs, GUIDs, and unique identifier generation

A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify information in computer systems without requiring a central registration authority. It is standardized by RFC 4122 (now superseded by RFC 9562) and represented as a 32-character hexadecimal string in 5 groups separated by hyphens: 8-4-4-4-12 (e.g., 550e8400-e29b-41d4-a716-446655440000). The total length is 36 characters including the 4 hyphens. UUIDs can be generated by any system independently and are statistically guaranteed to be unique — the probability of collision among v4 UUIDs is roughly 1 in 5.3 × 10^36 for a trillion UUIDs.

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UUID Generator Online

How to Generate UUIDs

Choose a UUID Version

Set Count & Format

Generate, Copy & Use

UUID v1 vs v4 vs v5 vs v7 — Which Should You Use?

5 UUID Output Formats

Everything in One UUID Tool

UUID v4 — Cryptographically Random

UUID v1 — Time-Based

UUID v5 — Namespace + Name (SHA-1)

UUID v7 — Timestamp-Sortable

Bulk Generation (1–1000)

5 Output Formats

Copy & Download

100% Private — Runs in Browser

When and Why to Use UUIDs

Database Primary Keys

API Request Tracing

Idempotency Keys

File & Asset Naming

Session & Token IDs

Test Data & Seed Fixtures

The Developer's Complete Guide to UUIDs

What Is a UUID — The 128-Bit Identity Standard

UUID v4 vs v7 — Which Should You Use for Database Keys?

UUID v5 — Deterministic IDs for Content-Addressed Systems

UUID Security — When Random IDs Protect Your Data

UUID in Distributed Systems and Microservices

How to Store UUIDs Efficiently

UUID Best Practices

Use UUID v7 for New Database Primary Keys

Use Native UUID Types, Not VARCHAR

Add Correlation IDs to Every API Request

Never Use Math.random() for IDs

Use UUID v5 for Content-Addressed Resources

What Developers Say

Frequently Asked Questions

Related Developer Tools

Need Custom ID Generation or Developer Tooling?

UUID Generator Online

How to Generate UUIDs

Choose a UUID Version

Set Count & Format

Generate, Copy & Use

UUID v1 vs v4 vs v5 vs v7 — Which Should You Use?

5 UUID Output Formats

Everything in One UUID Tool

UUID v4 — Cryptographically Random

UUID v1 — Time-Based

UUID v5 — Namespace + Name (SHA-1)

UUID v7 — Timestamp-Sortable

Bulk Generation (1–1000)

5 Output Formats

Copy & Download

100% Private — Runs in Browser

When and Why to Use UUIDs

Database Primary Keys

API Request Tracing

Idempotency Keys

File & Asset Naming

Session & Token IDs

Test Data & Seed Fixtures

The Developer's Complete Guide to UUIDs

What Is a UUID — The 128-Bit Identity Standard

UUID v4 vs v7 — Which Should You Use for Database Keys?

UUID v5 — Deterministic IDs for Content-Addressed Systems

UUID Security — When Random IDs Protect Your Data

UUID in Distributed Systems and Microservices

How to Store UUIDs Efficiently

UUID Best Practices

Use UUID v7 for New Database Primary Keys

Use Native UUID Types, Not VARCHAR

Add Correlation IDs to Every API Request

Never Use Math.random() for IDs

Use UUID v5 for Content-Addressed Resources

What Developers Say

Frequently Asked Questions

Related Developer Tools

Need Custom ID Generation or Developer Tooling?