Overview
A UUID is a 128-bit label written as 32 hex digits in five groups — the familiar 8-4-4-4-12 pattern. Version 4 means 122 of those bits are pure randomness, which makes accidental collision so unlikely that systems routinely generate IDs on disconnected devices and merge them later without a second thought. No central registry, no coordination, no clashes.
This tool produces them to the letter of the standard: the version nibble reads 4, the variant bits are set correctly, and the randomness comes from your browser's cryptographic generator rather than a weak shuffle. Take one, take fifty, strip the hyphens for compact storage, flip to uppercase for the system that demands it — then copy the batch or download it as a text file.
What does 'version 4' mean?
UUIDs come in versions that describe how they were made. Version 1 mixes a timestamp with a machine address; version 3 and 5 hash a name you supply; version 4 is 122 bits of randomness, period. It is the version you want when you just need unique IDs with no information baked in — no timestamps leaking, no machine identities exposed.
The maths behind the uniqueness claim is the birthday paradox in reverse: with 122 random bits, you would need to generate about a billion UUIDs per second for a century before a collision became likely. 'Never' is doing a lot of work in that sentence, but for every practical purpose, two version-4 UUIDs will never be the same.
Features
- Batches of 1 to 50 — one identifier for a quick test, fifty for an import or seed data.
- True version-4 format: the version nibble reads 4 and variant bits follow the standard exactly.
- Hyphens on or off — classic grouped form or a compact 32-character string.
- Uppercase option for systems that expect capital hex digits.
- Copy all in one click — the whole batch to your clipboard, one UUID per line.
- Download as .txt — save the batch as a plain text file for scripts and fixtures.
- Cryptographic randomness from your browser's secure source, not Math.random.
Benefits
- Zero coordination. Generate IDs anywhere; merging later just works.
- No leakage. Version 4 embeds no timestamps or machine addresses.
- Script-ready output. Copy or download straight into imports, tests and migrations.
- Private and free. No account, no API key, no usage counter.
Who can use it
Developers seeding databases, writing migrations, or generating test fixtures. QA engineers who need plausible unique IDs for test cases. Data folks preparing imports where every row needs a stable key. Anyone integrating with an API that asks for an idempotency key or a request ID — a fresh UUID per call is the standard answer.
How to use
- Choose how many UUIDs you need — anywhere from 1 to 50.
- Toggle hyphens and uppercase to match the format your system expects.
- Click generate (or just load the page — a fresh batch appears automatically).
- Copy the whole batch with one click, or download it as a .txt file.
- Paste them into your database, fixture file or API call and move on.
Frequently asked questions
Could two UUIDs ever be identical?
In theory yes, in practice no. With 122 random bits, you would need to generate absurd quantities — billions per second for a century — before a collision became plausible. For every real system, version-4 UUIDs are effectively unique without any coordination.
Should I keep the hyphens?
Keep them for readability and for any system expecting the canonical 8-4-4-4-12 form. Strip them when storage is tight or an API documents the 32-character compact form. Both represent the same 128 bits — it is purely a formatting choice.
Does uppercase vs lowercase matter?
UUIDs are case-insensitive by specification, so 'a' and 'A' mean the same thing. Some systems, logs or style guides prefer one; the toggle exists for those. When in doubt, lowercase is the more common convention.
Are these safe as database primary keys?
Yes — that is one of their main jobs. The trade-off versus auto-increment integers is size (16 bytes) and random insertion order, which can fragment some indexes. Many teams accept that for the benefit of generating keys anywhere without coordination.
Why not just use Math.random()?
Because it is not cryptographic — its output can be predictable, and UUIDs sometimes guard things that matter. This tool uses your browser's secure random generator, the same source behind the password tools here.
Do I need an account or anything installed?
No. Open the page, take your UUIDs, leave. Nothing is stored, nothing is tracked, and there are no quotas.
Conclusion
Unique IDs are one of those quiet foundations everything else stands on. Generate them properly — real randomness, correct format — and collisions become a problem you simply never think about again.