UUID Generator
A UUID (universally unique identifier) is a 128-bit ID, usually written as 36 characters with hyphens, used to label records without a central counter. FreeToolsKit's generator creates version 4 UUIDs — the fully random kind — using your browser's cryptographic random source, in batches of up to 100. Generated IDs are created on your device and never recorded.
Last updated: October 20, 2026
Inspect a UUID
Key takeaways
- UUIDs are version 4, generated with crypto.randomUUID — cryptographically random, not sequential.
- Generate from 1 to 100 UUIDs per batch, with toggles for uppercase letters and hyphens.
- Copy a single ID with one click, or the whole batch with “Copy all”.
- The inspector reads any pasted UUID and reports its version, variant and whether it is valid.
How do you generate UUIDs?
- Set how many UUIDs you need — 10 is the default, up to 100 per batch.
- Choose uppercase if your system expects it, and keep hyphens on for the standard format.
- Press Generate to produce a fresh batch.
- Copy individual IDs from their rows, or press “Copy all” for the whole list.
- Paste any existing UUID into the inspector to check its version and validity.
What is the UUID Generator used for?
- Seeding a database with primary keys for test or demo records.
- Naming uploaded files so two users can never collide on the same name.
- Creating correlation IDs for logging and tracing requests across services.
- Generating idempotency keys so a retried API call is never processed twice.
- Labelling rows in a spreadsheet or CSV before importing it into a database.
Frequently asked questions
What makes these version 4 UUIDs?
Version 4 means the ID is built from random bits, with the version (4) and variant fixed in specific positions — you can spot the “4” starting the third group. Random v4 IDs need no coordination: any device can mint them independently.
Could two generated UUIDs ever be identical?
In practice, no. A v4 UUID has 122 random bits, so you would need to generate billions before a collision became remotely plausible — the odds are far lower than everyday risks like hardware failure.
What does the inspector check?
It verifies the 8-4-4-4-12 hexadecimal structure, reads the version digit (1–5 in defined versions) and the variant bits, and tells you whether the string is a well-formed UUID at all.
Should I use uppercase or remove the hyphens?
Most systems accept any case, and the hyphenated lowercase form is the written standard. Only change the toggles if the system you are pasting into demands a specific format — a database column type of UUID accepts the standard form as-is.
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