UUID

Detailed Explanation

A UUID (Universally Unique Identifier) is a 128-bit identifier that looks like this: 550e8400-e29b-41d4-a716-446655440000. It's used as the primary key for rows in a database table.

Why UUIDs Instead of Numbers?

You might wonder why not just use 1, 2, 3 as IDs. UUIDs solve several problems:

• No collisions — Two different systems can generate UUIDs independently and they'll never clash
• Security — You can't guess someone else's ID (with numbers, if your ID is 5, you know ID 4 and 6 exist)
• Distributed systems — Multiple servers can create records simultaneously without coordinating

UUIDs in Supabase

Supabase uses UUIDs everywhere. When you create a table, the id column is typically a UUID that auto-generates using gen_random_uuid(). The auth.users table also uses UUIDs, so when you create a foreign key like user_id, it references a UUID.

In Practice

You rarely type UUIDs yourself. The database generates them automatically. You just reference them in queries and foreign keys:

CREATE TABLE notifications (
  id UUID DEFAULT gen_random_uuid() PRIMARY KEY,
  user_id UUID REFERENCES auth.users(id)
);

UUIDs are standard across SQL databases and are the default ID type in modern web development.