Tool guide

About UUID Generator

A UUID v4 generator creates random 128-bit identifiers that are safe to use as request IDs, database keys, test records, and correlation IDs when a central counter is not practical.

This tool can generate one or many IDs, switch uppercase output, remove hyphens for compact storage, and also offers UUID v7 when you need time-sortable identifiers.

How to use the UUID v4 Generator

Choose UUID v4 for random identifiers, or UUID v7 when chronological sorting is useful.
Set the count before generating if you need a batch for fixtures, seed data, or manual testing.
Turn on uppercase only when a legacy system expects it; lowercase UUIDs are the common default.
Use the no-hyphen option only if the target field or protocol requires the compact 32-character form.

When you would use it

Create correlation IDs for API requests so logs from different services can be tied together.
Generate stable test records without relying on a database sequence or auto-increment value.
Prepare placeholder IDs for mock JSON, OpenAPI examples, or frontend fixtures.
Use UUID v7 for event rows or audit records that should remain roughly sortable by creation time.

UUID format and practical details

A standard UUID is 36 characters including hyphens, usually shown as 8-4-4-4-12 hexadecimal groups. UUID v4 is random; UUID v7 combines a timestamp with random bytes for sortable IDs.

UUID v4: random identifier, good for most application IDs and request IDs.
UUID v7: time-ordered identifier, useful when database indexes benefit from insertion order.
Hyphenless form: the same 128-bit value without separators, often used in compact storage fields.
Case: UUIDs are hexadecimal, so uppercase and lowercase represent the same value in normal comparisons.

UUID v4 Generator FAQ

Is a UUID v4 really unique?: It is probabilistically unique. With a secure random source, collisions are so unlikely that UUID v4 is safe for typical application IDs.
When should I use UUID v7 instead of v4?: Use UUID v7 when you want IDs that sort roughly by creation time, especially for logs, events, or database indexes.
Should UUIDs be uppercase or lowercase?: Lowercase is the usual web and JSON convention. Uppercase is mainly for systems or documents that require that display style.
Can I remove the hyphens?: Yes, the value is equivalent without hyphens, but keep the standard hyphenated form unless your storage field or API contract asks for compact IDs.
Are generated UUIDs sent to the server?: No. Generation and formatting happen in the browser, so the generated IDs are not uploaded to wetool.site.

UUID vs auto-increment IDs

Auto-increment IDs are short and readable but require a central database sequence. UUIDs are longer, yet they work well across clients, queues, and distributed services where records may be created before they reach the database.

When UUID v4 is a good fit

UUID v4 works well when IDs must be generated offline, merged across systems, or exposed without revealing a sequence. It is not the default answer for every ID.

Use random UUIDs for client-side temporary IDs, distributed task IDs, test fixtures, and public share links.
For database primary keys where index locality matters, evaluate UUID v7, ULID, or database auto-increment IDs.
Do not treat a UUID as an authorization token; hard to guess is not the same as access control.

Collision probability and randomness source

UUID v4 depends on high-quality randomness. Browser generators should use Web Crypto level randomness, not Math.random().

A standard v4 UUID has about 122 random bits, so collision probability is extremely low for normal application volumes.
After bulk generation, a dedupe check can still catch copy/paste mistakes or script reuse errors.
UUID v4 does not contain time information; store created_at separately or use a time-ordered ID when sorting or tracing by time matters.