How are UUID v4 values generated?

UUID v4 values come from the browser's Web Crypto API to ensure cryptographically secure randomness.

What is the chance of collisions?

Collisions are astronomically unlikely (1 in 2^122). You can safely generate millions without repeats.

Where can I use these UUIDs?

Use them for database keys, identifiers, or tokens when you need uniqueness without coordination.

Can I generate several UUIDs quickly?

Press generate as often as you like or copy the value each time; every click produces a fresh, random identifier.

Are UUIDs stored after I close the page?

No, values exist only in the current session and disappear once you refresh or navigate away.

UUID v4 generator

Generate secure version 4 UUIDs with the Web Crypto API. Nothing leaves your browser.

Latest UUID

UUID v4 contains 122 bits of randomness. Collisions are practically impossible.

Understanding UUID formats

Universally Unique Identifiers (UUIDs) are 128-bit values rendered as 32 hexadecimal characters separated into an 8-4-4-4-12 pattern. Different versions dictate how those bits are filled, which influences ordering, source data, and collision guarantees.

Version	Source	Sort order	Typical usage	Notes
UUID v1	Timestamp + MAC address	Chronological	Legacy systems needing time ordering	Leakes host metadata. Avoid in privacy sensitive contexts.
UUID v4	122 bits of randomness	Unordered	Default choice for distributed IDs	Collisions are astronomically unlikely when generated with CSPRNG.
UUID v7	Unix timestamp + randomness	Roughly sortable	Event stores, databases that benefit from time ordering	Draft standard gaining adoption. Great compromise between randomness and sorting.

Choosing the right identifier

Pick the UUID version that suits your application's scaling, privacy, and ordering requirements. These scenarios outline when to stick with v4 and when to consider alternatives.

Stateless APIs

v4 is ideal when microservices or clients generate identifiers independently and you only care about uniqueness, not sort order.

Append-only databases

For workloads that benefit from chronological clustering, UUID v7 or ULIDs maintain time ordering while preserving compatibility with UUID tooling.

Security-sensitive tokens

UUIDs are predictable enough to enumerate once discovered. For secrets, issue cryptographically random bytes and deliver them over TLS, or use JWTs with proper claims.

Implementation guidelines

A few simple habits keep UUIDs reliable across environments and databases.

Use canonical lower-case hex to avoid case-sensitive comparisons in systems that normalize strings.
Store as native UUID types where supported (PostgreSQL, SQL Server) for faster indexing and validation.
Validate input format when accepting UUIDs from clients to prevent injection into dynamic queries.
Don't expose MAC addresses; avoid UUID v1 in public APIs to protect host metadata.

Quick question

Do you need UUIDs for high-throughput systems or occasional identifiers?

UUID generator FAQ

What is a UUID and how is it structured?

A UUID is a 128-bit identifier rendered as 8-4-4-4-12 hexadecimal characters. Versions such as v4 or v7 control how the bits are derived—randomness for v4, timestamp plus randomness for v7.

How unlikely is a UUID v4 collision?

UUID v4 leaves 122 bits of randomness, making collisions astronomically unlikely. You can generate billions before a statistically significant collision chance appears.

When should I use UUID v4 versus UUID v7?

Choose v4 for maximum randomness and ease of generation. Select v7 when you need roughly sortable identifiers that still work with UUID-aware databases.

Are UUIDs secure enough for secrets?

UUIDs provide uniqueness, not confidentiality. They make great identifiers, but use randomly generated tokens or encrypted payloads for anything sensitive.

Does this generator send identifiers to a server?

No. HashyTools uses the Web Crypto API directly in your browser so generated UUIDs never leave your device.