UUID Generator: Free Random UUID v4 Maker

This UUID generator creates random version 4 UUIDs that you can copy straight into code, databases, test data or config files. Pick a quantity from 1 to 100, switch on uppercase or remove the hyphens if your system needs it, and copy one value or the whole list in a click.

What Is a UUID?

A UUID (universally unique identifier) is a 128-bit value used to label records, files, sessions or devices without a central system handing out numbers. It is written as 32 hexadecimal digits, and the standard text form groups them as 8-4-4-4-12 with hyphens, which makes 36 characters. In Microsoft environments the same format is called a GUID, so the two names describe the same thing.

This tool produces version 4 UUIDs. In a v4 UUID, 122 of the 128 bits are random and the other six bits mark the version and variant. You can spot one by the first character of the third group, which is always 4, and the first character of the fourth group, which is always 8, 9, a or b. That leaves roughly 5.3 x 10^36 possible values.

How Likely Is a Duplicate?

A duplicate is practically impossible in normal use. Birthday-paradox math says you would need to create about 2.7 quintillion v4 UUIDs before reaching even a 50% chance of a single collision. A system creating a million UUIDs every day would need billions of years to get there.

How to Use the UUID Generator

You can get a usable UUID in one step, because a value is already waiting in the box at the top when the page loads. For larger batches, follow these steps.

1. Copy the value in the box with the Copy button beside it, or click Regenerate to replace it with a fresh single UUID.
2. Open the Quantity menu and choose 1, 5, 10, 25, 50 or 100.
3. Tick Uppercase if you want capital letters (A to F instead of a to f).
4. Tick No hyphens if you want a continuous 32-character string.
5. Click Generate. With a quantity above 1, a Generated UUIDs list appears below the controls. With a quantity of 1, the box at the top simply updates.
6. Click Copy All to copy the whole list with one UUID per line, or use the small copy icon on a single row.

The checkboxes apply at the moment a value is created. If you change Uppercase or No hyphens after generating, click Generate or Regenerate again to see the new format.

Worked Example: Five IDs for Test Data

Say you are seeding a development database and need five order IDs in a compact format. Set Quantity to 5, tick No hyphens, and click Generate. You get five lines, each 32 characters long, and Copy All puts them on your clipboard ready to paste into a spreadsheet or a fixture file.

Here is how one sample value changes with each option:

In the sample, the third group starts with 4 (version 4) and the fourth group starts with a (a valid variant character). Your generated values will differ, but they always follow that pattern.

How Do You Read and Check the Results?

A correct result is easy to verify by length and pattern. With hyphens, expect 36 characters; without hyphens, expect 32. Every character must be a digit or a letter from a to f.

• Third group starts with 4: confirms version 4. If you see another digit, the value was not made by this tool or was edited.
• Fourth group starts with 8, 9, a or b: confirms the standard variant.
• Different every time: two lines that match would mean a copy and paste error, not a generator collision.

Hex digits are not case sensitive, so uppercase and lowercase forms represent the same UUID. The mistake comes from comparing them as plain strings. If your code stores one style, convert every incoming value to that style before comparing.

UUID v4 or v7: Which One Do You Need?

Use v4 when you want an identifier with no meaning, and v7 when you want identifiers that sort by creation time. A v7 UUID, defined in RFC 9562, starts with a Unix timestamp in milliseconds followed by random bits. A v4 UUID has no time component at all.

The difference matters for large indexed database tables. Random v4 keys land all over an index, which can slow inserts at scale, while time-ordered keys append near the end. For test data, request IDs, correlation IDs, file names and most application records, v4 works well. This page generates v4 only, so if you need v7, create it in your application code or database.

Who Uses a UUID Generator?

Anyone who needs a unique label quickly, without writing code first, can use it. Common situations include:

• Developers filling fixtures, mock API responses, or seed files with realistic primary keys.
• QA testers who need many distinct IDs to test imports, bulk endpoints or duplicate handling.
• Database admins who need a one-off key for a manual insert or a migration script.
• Technical writers and support teams who need believable sample IDs for documentation, tickets and screenshots.
• Config authors who need an instance, tenant or device identifier for a settings file.

If you paste your new IDs into JavaScript or HTML fixtures, the code beautifier can tidy the surrounding code. When a UUID travels inside an encoded payload, the Base64 encoder and decoder helps you inspect it. To confirm that two fixture files differ only where you expect, run them through the code diff tool.

Best Practices and Common Mistakes

Treat a UUID as an identifier, not a secret

A v4 UUID is random, but IDs get logged, shared in URLs and pasted into tickets. Do not use one as a password, an API key or the only barrier protecting private data. Use proper authentication for access control.

Store it efficiently

If your database has a native UUID type, use it. It stores 16 bytes, while the same value saved as 36 characters of text takes more than twice the space and makes indexes larger.

Keep one format

Pick lowercase with hyphens, or whatever your stack expects, and use it everywhere. Mixed formats are the most common reason a lookup fails even though the ID exists.

Do not hand-edit digits

Changing characters inside a UUID can break the version and variant markers, and some validators will then reject it. Generate a new one instead.

Generate in code for production

For IDs created while your application runs, use your platform's own function: uuid.uuid4() in Python, UUID.randomUUID() in Java, crypto.randomUUID() in JavaScript, or gen_random_uuid() in PostgreSQL. This page is best for one-off values and batches you paste by hand.

Quick troubleshooting

• The format did not change: click Generate or Regenerate after toggling a checkbox.
• No list appears: a quantity of 1 updates the top box only. Choose 5 or more to see the Generated UUIDs list.
• You need more than 100: click Generate again and paste each batch, or create them in code.
• An ID is rejected as invalid: check for stray spaces, missing hyphens or a required uppercase style.

What This UUID Generator Does Not Do

The tool creates new random v4 values only. It does not produce v1 or v7 UUIDs, validate or decode existing ones, or look up Minecraft players. A Minecraft UUID is an account identifier assigned by the game's services, so a random value from this page will not match any real player.

Uniqueness here is statistical. If your application needs a hard guarantee, keep a unique constraint on the column so a freak duplicate is rejected instead of silently stored.

You now know what a UUID is, how v4 differs from v7, and how to format the output for your system. Choose a quantity, set your options and click Generate to get your identifiers. For more utilities like this one, browse the web developer tools collection.