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UUID Generator

Generate random version 4 UUIDs (also called GUIDs) in one click, or create up to 10,000 at a time. Copy them, download them as a text file, or check whether a UUID is valid. It all happens in your browser, and nothing is uploaded.

  • Free
  • · No signup
  • · Nothing uploaded
  • · Bulk generation & validator

Private by design. UUIDs are generated locally in your browser using its secure random number generator. They are never uploaded, Q3 Labs doesn't store them, and no account is needed.

Generate UUIDs (version 4)

Custom amount: 1 to 10,000.

Format

Changing the format re-styles the UUIDs you already have. It doesn't generate new ones.

Validate a UUID

Paste a UUID to check its structure and see its version and variant. This is a format check only. It can't tell you whether a UUID is genuine, unused or trustworthy.

What is a UUID?

A UUID, or Universally Unique Identifier, is a 128-bit label used to identify information in computer systems. It is written as 32 hexadecimal digits, normally in five hyphen-separated groups. The idea is that anyone can create one at any time, anywhere, without asking a central registry, and the chance of two independently created UUIDs being the same is negligible.

UUIDs are specified in RFC 9562, which replaced the earlier RFC 4122. They are widely supported: most programming languages, databases and frameworks can generate, store and parse them.

What is a UUID v4?

Version 4 is the randomly generated UUID. Of its 128 bits, 6 are reserved to record the version (4) and the variant, and the other 122 bits come from a random number generator. That gives about 5.3 × 1036 possible values. Version 4 is popular because it needs no clock, no machine identifier and no coordination. A random source is all it takes.

How good the result is depends on the random source. This tool uses your browser's cryptographically secure generator, not a general-purpose pseudo-random function.

How UUID generation works

  1. Get secure random bytes. Modern browsers provide crypto.randomUUID() (in secure contexts such as HTTPS pages), which returns a ready-made version 4 UUID.
  2. Fall back safely. If it isn't available, the tool reads 16 bytes from crypto.getRandomValues(), sets the version and variant bits itself, and formats the result.
  3. Never guess. If a browser offers neither, the tool reports an error. It doesn't substitute a predictable random function.

UUID format explained

A UUID is written in the pattern:

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

  • Each x is a hexadecimal digit (0–9, a–f). The groups have 8, 4, 4, 4 and 12 digits: 32 in all, 36 characters with the hyphens.
  • M is the version. In a version 4 UUID it is always 4, so the third group starts with 4.
  • The first digit of N holds the variant. For standard UUIDs it is 8, 9, a or b.
  • Example: 550e8400-e29b-41d4-a716-446655440000

Hyphens are a text convention. The same value can be written without them (32 digits), and upper- or lowercase mean the same thing. Both options are available above.

UUID vs GUID

GUID stands for Globally Unique Identifier. It is the name Microsoft uses, particularly in Windows and the .NET ecosystem, for the same general kind of 128-bit identifier that the rest of the industry calls a UUID. In everyday use, the text form of a GUID and a UUID look the same and are used interchangeably.

The names aren't identical in every detail across every implementation. For example, some systems store the bytes of the first fields in a different order in binary form, so if you exchange raw binary values (not text), confirm the byte order. When you search for a "GUID generator", a version 4 UUID is what you'll normally want.

UUID use cases

Database records

Give every row a globally unique key that can be created by the application, before or without asking the database.

API identifiers

Use UUIDs as resource IDs in URLs and responses, so identifiers aren't simple counters that reveal how many records exist.

Application objects

Tag files, sessions, jobs, events and messages with an ID that won't clash with one created elsewhere.

Request and trace IDs

Attach a unique ID to each request so a single action can be followed across logs and services.

Distributed systems

Several servers, devices or offline clients can create IDs independently without coordinating.

Test data and development

Generate a batch of realistic identifiers for fixtures, seed scripts, mocks and documentation examples.

UUIDs in databases, APIs and web development

Databases. UUIDs make good primary keys when records are created in many places, because the application can assign the ID up front. Prefer the database's native UUID type where there is one (rather than storing the text), since it's more compact. Random version 4 keys can scatter inserts across an index and are larger than integers, and some teams choose a time-ordered version such as v7 to improve locality. Measure with your own workload before deciding.

APIs. A UUID in a URL, such as /orders/550e8400-…, is harder to enumerate than /orders/1042, and it can be created by the client. It is not an access control. Always verify permissions on the server.

Web development. UUIDs are handy for React list keys generated once, idempotency keys, upload names, correlation IDs in logs and test fixtures. If you're planning an application or API, our web development team can help you choose sensible identifiers and data models.

How to generate a UUID, generate several, and validate one

One UUID: leave the quantity at 1 and press Generate UUID. Use Copy, or Regenerate for a new one.

Many UUIDs: choose a preset or type a custom quantity (up to 10,000), press Generate, then Copy all or Download .txt. Untick "Include hyphens" or tick "Uppercase" to change how the list is written. The values stay the same, only their style changes.

Validate: paste a UUID into the validator and press Validate UUID. Surrounding spaces, upper case, braces and a urn:uuid: prefix are all understood; anything else malformed is rejected with a reason. Version and variant are reported only when they can be identified reliably.

Are UUIDs secure?

UUIDs are identifiers. A version 4 UUID made by a cryptographically secure generator is unpredictable, and that's a useful property for IDs. But an identifier isn't automatically a secret. UUIDs end up in URLs, logs, analytics and screenshots, and the format was never designed as a credential.

  • Don't use a UUID as a password, an API secret, a session or authentication token, a password-reset token or an encryption key.
  • Don't treat "hard to guess" as a substitute for access control.
  • Collisions between random UUIDs are extraordinarily unlikely, but not impossible, so keep a uniqueness constraint wherever a duplicate would cause harm.
  • A valid-looking UUID says nothing about whether it was issued by your system or anyone you trust.

UUID version overview

Standard UUID versions and what they are based on
VersionBased onNotes
1Time-basedBuilt from a timestamp and a node identifier.
2DCE securityA rarely used variation of version 1.
3Name-based (MD5)The same namespace and name always produce the same UUID.
4RandomMostly random bits. This is what this tool generates.
5Name-based (SHA-1)Like version 3, using SHA-1 for hashing.
6Reordered time-basedVersion 1 timestamps arranged so values sort by time.
7Unix timestamp-basedA millisecond timestamp plus random bits; sorts by creation time.
8CustomSpace for vendor-specific or experimental layouts.

Two special values also exist: the nil UUID (all zeros) and the max UUID (all ones). This tool generates version 4 and can identify these versions in the validator.

Frequently Asked Questions

Explore more

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