When you need a UUID
API fixtures, temporary client-side keys, and requestId values in logs all need a globally unique, unpredictable id. Hand-typing or copying real production IDs is risky.
ComTools UUID Generator (Tools/Developer/Uuid) calls crypto.randomUUID() locally and returns a standard UUID v4 (lowercase, hyphenated).
What UUID v4 looks like
36 characters including four hyphens:
xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
Example:
3f9a1c2e-8b4d-4e6a-9c1f-2a7b5d8e0f12
- Position 13 is version
4 - Variant bits follow RFC 4122
- Entropy comes from the browser’s secure random source
Steps
- Open UUID Generator.
- A value is generated on load; click Generate for a new one.
- Copy into code, config, or SQL.
Nothing is uploaded.
vs the GUID tool
| Tool | Output |
|---|---|
| UUID Generator | Lowercase v4, e.g. a1b2c3d4-... |
| GUID Generator | Same algorithm, uppercase (.NET / SQL Server style) |
Pick GUID when you want uppercase without a separate transform.
Common scenarios
| Scenario | Tip |
|---|---|
Sample JSON id |
Paste into JSON Formatter |
SQL IN (...) tests |
Combine with URL Params IN copy or IN (N'...') |
| Bulk fake rows | Fake data has a uuid column type |
| Correlation IDs | One UUID per request in logs |
Notes
- Each click yields a new random value (input is ignored).
- Needs
crypto.randomUUID(modern browsers). - A UUID is not a cryptographic secret and is not time-ordered (unlike v1/v7).
Related
FAQ
Many UUIDs at once?
One per generate click—or use fake data for a uuid column.
32 hex chars without hyphens?
Generate, then strip - yourself; this page outputs the canonical form.
Collision risk?
Negligible for v4 in practice—still do not treat UUID alone as auth.