UUID Generator
Generate v4 (random) or v1 (time-based) UUIDs in bulk — copy one or all, toggle uppercase, runs entirely in your browser.
Set a count above to generate UUIDs.
All UUIDs are generated locally in your browser. Nothing is sent to a server.
What Is a UUID Generator?
This tool creates Universally Unique Identifiers (UUIDs) on demand — up to 100 at a time — entirely inside your browser. No server receives your request; no log records which IDs were issued. You choose the version, set the quantity, and click Regenerate to get a fresh batch instantly.
UUID v4 vs UUID v1 — Which Should You Choose?
Both versions produce a string of the same shape (eight-four-four-four-twelve hexadecimal digits separated by hyphens), but they differ in how the bits are filled:
- v4 (random) — 122 of the 128 bits are drawn from a cryptographically secure random source. The remaining six bits encode the version and variant. There is no embedded timestamp and no machine identity — making v4 the safest choice whenever privacy matters. This is the default and right pick for database primary keys, request trace IDs, and user-facing tokens.
- v1 (time-based) — encodes the current clock time at 100-nanosecond resolution plus a node identifier (historically the MAC address). v1 UUIDs sort naturally in roughly chronological order. They are useful when you need to reconstruct insertion order from the UUID alone, or when debugging distributed systems where knowing when an ID was issued helps you trace events across services.
Common Use Cases
Developers reach for UUID generators in a wide range of situations:
- Database primary keys — generate IDs in the application layer so inserts can be prepared offline and replicated without sequence conflicts across shards.
- File naming — avoid collisions when writing user-uploaded files to object storage (S3, GCS) without a coordinating sequence.
- Correlation IDs — attach a UUID to every HTTP request so logs across microservices can be joined on a single field.
- Seed data & fixtures — populate test databases with deterministic but unique IDs so tests do not depend on auto-increment sequences.
- Client-side draft IDs — assign a UUID to a form or wizard before the user submits so the server can detect duplicate submissions (idempotency).
How to Use This Tool
Select v4 or v1 from the version tabs, enter how many UUIDs you
need (1–100), and press Regenerate. Each UUID appears in its own row with a
per-row Copy button. Toggle Uppercase if the target system
expects capital hex letters. Use Copy all to put every UUID in the list onto
your clipboard as newline-separated text — handy for pasting directly into a SQL
INSERT statement or a spreadsheet.
Privacy
UUID generation runs entirely in your browser using the uuid library, which in turn
calls the Web Crypto API for all randomness. No network request is made, no UUID is stored, and
nothing is logged. The tool is safe to use in air-gapped environments or anywhere data-handling
policies restrict online services.
Frequently Asked Questions
What is a UUID and what is it used for?↓
A UUID (Universally Unique Identifier) is a 128-bit label standardised by RFC 4122. It is formatted as 32 hexadecimal digits split into five groups separated by hyphens — for example 550e8400-e29b-41d4-a716-446655440000. UUIDs are used as primary keys in databases, as request correlation IDs in distributed systems, as file names to avoid collisions, and anywhere a unique token needs to be created without coordinating with a central authority.
What is the difference between UUID v4 and UUID v1?↓
UUID v4 is generated from cryptographically random bits. The only fixed bits are the version (4) and the variant, giving about 122 bits of randomness — making collisions astronomically unlikely even at scale. UUID v1 is time-based: it encodes the current timestamp plus the MAC address of the machine generating it, which makes the time of creation derivable from the UUID itself. v4 is preferred for most applications because it is both random and private; v1 is useful when you need to sort UUIDs chronologically or trace when a record was created.
Are UUIDs truly unique? Could two be the same?↓
For v4 UUIDs the probability of a collision is so small it is effectively impossible in practice. Generating 1 billion UUIDs per second for 100 years would give a roughly 50% chance of a single collision — far below the failure rates of the hardware running any real system. For most applications you can treat v4 UUIDs as guaranteed unique.
Should I use uppercase or lowercase UUIDs?↓
RFC 4122 specifies lowercase hex digits and most databases, languages, and APIs follow that convention. However, many systems also accept uppercase and treat UUIDs case-insensitively. If you are storing UUIDs in SQL, use a UUID/GUID column type rather than VARCHAR so the database normalises casing for you. When inserting into a system that you do not control, check its documentation — and use the toggle here to match whatever format it expects.
Is it safe to generate UUIDs for production use in a browser tool?↓
Yes. The uuid library uses the Web Crypto API (crypto.getRandomValues) for v4 generation, which produces cryptographically strong random numbers — the same source used by password managers and key-generation tools. You can safely use these UUIDs in production databases, API tokens, or any context that needs a unique identifier.