When (and When Not) to Use UUIDs/GUIDs in Your Database and Code

Why Developers Reach for UUIDs/GUIDs

Auto-incrementing integer IDs (1, 2, 3...) are simple and fast, but they have real limitations that UUIDs/GUIDs solve. Understanding when each approach fits helps you avoid picking the wrong one for a given project.

Good Reasons to Use a UUID/GUID

Distributed systems and merging data: If multiple servers, databases, or offline clients might generate new records independently before syncing, auto-incrementing IDs will collide (two different records both claiming ID #47). UUIDs are generated independently with a vanishingly small collision probability, so records from different sources can merge safely without ID conflicts.

Not wanting to expose sequential information: An auto-incrementing ID in a public URL (like /orders/1042) leaks information — competitors or curious users can guess your order volume, or enumerate other users' records by simply changing the number. A UUID in that same URL position (/orders/550e8400-e29b-41d4-a716-446655440000) reveals nothing and can't be sequentially guessed.

Client-generated IDs before the record exists: Sometimes you need to know a record's ID before it's saved to the database — for example, to reference it in a form or optimistic UI update. A client can generate a UUID/GUID locally with no risk of collision, something impossible with server-assigned auto-increment IDs.

Merging or migrating databases: If you ever need to combine data from multiple database instances (after an acquisition, a multi-region setup, or a migration), integer primary keys almost always collide and need remapping. UUIDs generated independently avoid this problem entirely.

Good Reasons to Stick with Auto-Increment

Performance at scale: UUIDs are larger (128 bits vs typically 32 or 64 bits for integers) and, if used as a primary key with random (v4) values, can hurt database index performance due to poor locality — new rows insert at random points in the index rather than appending to the end. This matters more at large scale than in small applications.

Simplicity and readability: For internal tools, admin panels, or small projects, a simple auto-incrementing ID is easier to read, reference in conversation ("check ticket #204"), and debug than a long UUID string.

You don't actually need the properties UUIDs provide: If your application is a single database instance with no distributed writes, no public-facing sequential-ID leakage concern, and no need for client-side pre-generation, the extra complexity of UUIDs may not be buying you anything.

A Middle Ground: Sequential/Time-Ordered UUIDs

If you want the collision-safety of a UUID but better database index performance, consider a time-ordered variant (like UUID v7 or similar sequential UUID formats some databases/libraries support) — these preserve most UUID benefits while inserting more predictably into indexes, at the cost of leaking rough creation-time ordering (which is usually an acceptable tradeoff, since it's far less specific than a plain sequential integer).

Quick Decision Guide

• Single database, internal tool, low scale → auto-increment integer is fine
• Distributed writes, offline-first apps, or multi-database merges → UUID/GUID
• Public-facing IDs where you don't want sequence/volume exposed → UUID/GUID
• Need the ID before the record is saved (client-generated) → UUID/GUID
• High-write-volume single database and index performance is critical → auto-increment, or a time-ordered UUID variant as a compromise

Generating Test UUIDs/GUIDs

Whichever approach you land on, you'll likely need to generate sample UUIDs/GUIDs during development — for seeding test data, mocking API responses, or manually inserting records. Use our free UUID/GUID Generator to generate one or many at once, in your preferred case formatting.

Conclusion

UUIDs/GUIDs solve real problems — collision-free distributed generation, non-sequential public IDs, client-side pre-generation — but they're not automatically the better choice for every project. Match the ID strategy to your actual constraints rather than defaulting to either option out of habit.