What is a UUID and how do you generate one?
A UUID (Universally Unique Identifier) is a 128-bit value used to identify records, files, sessions and API requests without any central coordination. The most common version is UUID v4, generated from random numbers.
Why UUIDs instead of auto-increment IDs?
Sequential IDs leak information — anyone can guess how many users you have or fetch a neighbouring record. UUIDs are unpredictable and can be generated by any client or server independently, which is essential in distributed systems and offline-first apps.
The trade-off is size: a UUID is 36 characters as a string, larger than a 64-bit integer. For most applications the convenience and collision resistance are worth it.
How to generate a UUID with FreetoolsY
Open the UUID Generator and click generate. The tool creates RFC 4122 version-4 UUIDs using the browser's crypto.randomUUID or crypto.getRandomValues, so the values are cryptographically random and never leave your device.
- Generate one UUID or a batch of them at once.
- Choose the format (lowercase, uppercase or without hyphens).
- Copy with a single click and paste it into your database or code.
UUID v4 vs other versions
Version 4 UUIDs are random and are the right default for identifiers. Version 3 and 5 are deterministic — they are hashed from a name and namespace, useful when you need the same UUID for the same input. Version 1 and 7 embed a timestamp and are better when sortable, time-ordered IDs matter.
When a random string rather than a structured ID is what you need, the Random String Generator creates tokens of any length and charset.