UUID Generator
Generate UUID v4 and UUID v7 values in your browser for fixtures, database rows, and mock API ids.
UUIDs are generated locally with the Web Crypto API. Nothing is sent to a server.
UUID generator for fixtures and mock APIs
Create UUID v4 and UUID v7 identifiers in the browser. Copy one id or a batch for database rows, test fixtures, and mock API responses. Generation uses the Web Crypto API on your device.
What is a UUID?
A UUID is a 128-bit value defined in RFC 9562. The common text form is eight-four-four-four-twelve hexadecimal characters:
018f6b2e-7c3a-7a1b-8d4e-6f2c9a1b0e77
The version nibble says how the id was built. Version 4 is random. Version 7 embeds a Unix timestamp so ids created later sort after ids created earlier.
UUID v4 vs UUID v7
UUID v4 fills the id with random bits, aside from the version and variant markers. It is the default in browsers via crypto.randomUUID() and in most languages’ standard libraries. Random ids do not reveal when they were created and do not cluster in an index by time.
UUID v7 puts a 48-bit Unix millisecond timestamp in front, then random bits. New rows land near each other in a B-tree, which is why teams use v7 for primary keys. The timestamp is visible, so treat v7 as an id, not as a secret.
How to generate a UUID
- 1. Pick v4 or v7. Choose v4 for random ids and v7 when you want time-ordered ids.
- 2. Choose a count. Generate up to 100 ids at once for a seed file or a mock list endpoint.
- 3. Copy. Copy one line or the whole list. Turn on uppercase or remove hyphens if the API schema requires that shape.
Using UUIDs in mock API responses
Mock payloads look real when every record has a stable id. Generate a batch here, paste the ids into a JSON body, then format that body with the JSON formatter. The same ids work as path parameters when you exercise a frontend against MockFlow mock APIs.
Related tools
- Developer tools — browse every free MockFlow utility.
- JSON Formatter — format the payload after you drop ids in.
- Unix Timestamp Converter — UUID v7 embeds a Unix millisecond timestamp you can read here.
- HTTP Status Code Explorer — pick 201 Created when a mock endpoint returns a new id.
Frequently asked questions
- What is a UUID?
- A UUID (universally unique identifier) is a 128-bit id, usually written as 36 characters with hyphens, such as 550e8400-e29b-41d4-a716-446655440000. Databases, APIs, and distributed systems use UUIDs when they need an id that can be created without asking a central counter.
- What is the difference between UUID v4 and UUID v7?
- UUID v4 is random. UUID v7 starts with a Unix timestamp in milliseconds, then random bits, so newer ids sort after older ones. Use v4 when you only need uniqueness. Use v7 when insert order or roughly chronological sorting matters, such as primary keys in a database index.
- Does this UUID generator run in my browser?
- Yes. UUIDs are created with the Web Crypto API in your browser. They are not generated on a server and are not stored.
- Are these UUIDs safe to use as ids?
- Yes for application ids, fixtures, and mock API records. UUID v4 from crypto.randomUUID and UUID v7 built with crypto.getRandomValues are the standard random constructions from RFC 9562. They are identifiers, not passwords or secret tokens.
- Can I generate more than one UUID?
- Yes. Choose a count from 1 to 100, then copy a single id or copy the full list. Uppercase output and ids without hyphens are available when a schema requires that format.
- Is a GUID the same as a UUID?
- In everyday developer use, yes. GUID is the name Microsoft popularized for the same 128-bit identifier format. This generator produces the canonical hyphenated hexadecimal form used by both names.