How to generate UUID v4: Creating multiple · Saving JSON · Understanding the possibility of duplication

How to generate one or multiple UUIDs

1. Enter an integer between 1 and 1,000 in the number of creations.
2. Select one per line or JSON array.
3. Press Generate UUID.
4. Select Capitalization if necessary and copy or download the results.

If you click Generate UUID again, a new list will be created. On the other hand, changing only the output format and case will only change the representation of the values ​​you have already created. Changing the count erases the previous results and requires them to be regenerated. Save the values ​​you need before refreshing or leaving the page.

Download one per line as .txt and JSON array as .json file. The JSON output is an array of UUIDs wrapped as strings. When using it for database imports or API requests, check separately whether the target system requires an array or an object with a specific key.

36 character format and case of UUID v4

UUID is a 128-bit value. A typical text representation is the 32 hexadecimal characters divided by 8-4-4-4-12 followed by four hyphens, for a total of 36 characters. In v4, the first letter of the third group is 4, and the first letter of the fourth group is one of 8·9·a·b.

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
x: hexadecimal digit
y: 8, 9, a, or b

The above notation is a placeholder to describe the structure and is not the actual UUID to be used. Upper and lower case letters represent the same hexadecimal value. However, systems that compare general strings rather than UUID data types may treat case differently, so unify the storage and comparison rules. This tool does not provide hyphenation, braces, or URN prefix formatting.

Browser-generated method and duplicate check scope

This tool calls the browser's crypto.randomUUID(). This API provides v4 UUIDs using a cryptographically secure random number generator. Requires HTTPS and a supported modern browser; environments where these are not available will result in a creation failure. The generated values ​​are not sent to the tool server or stored in localStorage.

Once created, the list is checked for duplicates. It is not checked against previously created lists, other devices, or actual databases. Since UUID v4 is a random value, the probability of a collision is not mathematically zero. In systems where records must be separated, provide unique constraints and separate ways to handle conflicts. This page does not have the ability to manage records of multiple clicks on the Create button.

Implementation notes: MDN crypto.randomUUID().

UUID v4 and chronological sorting, using test data

v4 is not a format for expressing creation time order. Sorting the list alphabetically does not result in chronological order of creation. This tool only supports v4 and does not provide v1·v5·v7 generation or name-based deterministic ID calculation. Distinguish between tasks that always require the same ID for the same input and tasks that require a new, random ID.

When leveraging UUIDs in test data, you don't end up just creating row-specific IDs. Match together the IDs referenced by other tables, and keep the list you generate as testing material if you need to reproduce the results. This page does not provide database connections or automatic foreign key assignment.

Format/Version Note: RFC 9562 UUID Specification.

Authentication and authorization checks are required even with UUID

Access control is not complete just because addresses using UUID cannot be easily guessed. The service must separately check whether the user has permission to read or modify the document. The UUID itself does not encrypt data nor does it prove who owns the document.

This generator does not provide the ability to issue, expire, or destroy login tokens, store passwords, or manage secret keys. For authentication information for production services, use server-side design and management procedures appropriate for that purpose. When inserting the identifier created here into public code examples or test materials, it is a good idea to check whether it is a sensitive value associated with an actual account or document.

Frequently Asked Questions