UUID Generator
Generate one or many random version-4 UUIDs for use as database keys, identifiers, or test fixtures. This free online developer calculator runs entirely in your browser — no signup, no data sent anywhere.
Inputs
Results
How It Works (Formula & Method)
A version-4 UUID has the form xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. Each x is a random hex digit. The 4 marks the version, and the y position is constrained to 8, 9, A, or B to mark the variant. The remaining 122 bits are random, giving roughly 5.3 × 10³⁶ possible values.
Worked Example
Below is a worked example using the calculator's default values. The same numbers are pre-filled in the form above so you can press Calculate and see the result without typing anything.
Inputs used:
- How Many UUIDs (1–50): 5
With these inputs, the calculator computes the metrics shown in the Results panel. Change any value and press Calculate again to see how the result responds — the live widget and the chart both update instantly.
About the UUID Generator
A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit value used to label something uniquely without a central authority. Version 4 UUIDs are generated almost entirely from random numbers, so two systems can independently create IDs that will essentially never collide. They are the default primary-key format for many modern databases and distributed systems.
Tips & Considerations
- Version 4 UUIDs are random; version 1 UUIDs embed a timestamp and MAC address. Use v4 unless you specifically need ordering.
- UUIDs are 36 characters as text but only 16 bytes as binary — store them as binary in databases where space matters.
- These are generated in your browser with Math.random(). For cryptographic secrets, use a tool backed by a CSPRNG.
Frequently Asked Questions
Can two UUIDs ever be the same?
In theory yes, but the probability is astronomically small. You would need to generate billions of UUIDs per second for many years before a collision became likely.
What is the difference between a UUID and a GUID?
They are the same thing. "GUID" is the term Microsoft uses; "UUID" is the term in the underlying RFC standard.
Should I use a UUID as a database primary key?
UUIDs avoid coordination between servers, which is great for distributed systems. The trade-off is larger keys and, for v4, no natural sort order — consider UUIDv7 if ordering matters.
What does the UUID Generator compute?
The UUID Generator takes 1 input value and returns 1 result. Generate random version-4 UUIDs (GUIDs) for database keys, API tokens, and test data — up to 50 at once.