UUID v4 vs v7: Which Should You Use in 2026?

UUIDs Are Everywhere

Universally Unique Identifiers (UUIDs) are 128-bit values used to identify resources without a central authority. They look like this:

550e8400-e29b-41d4-a716-446655440000

If you've built a web app, you've used UUIDs — for user IDs, session tokens, API keys, database primary keys, or trace IDs.

UUID v4: The Random Standard

UUID v4 is the most widely used version. It's 122 bits of random data plus 6 bits of version/variant info.

Pros:

• Truly random — no information leakage
• Supported everywhere
• Simple to generate

Cons:

• Not sortable by time
• Poor database index performance (random insertion)
• No embedded timestamp

UUID v7: The New Default

UUID v7 (RFC 9562, finalized 2024) embeds a Unix timestamp in the first 48 bits, followed by random data.

Pros:

• Time-sortable — newer IDs sort after older ones
• Excellent database index performance (sequential insertion)
• Embedded timestamp for debugging
• Still unique enough for distributed systems

Cons:

• Leaks creation time (privacy consideration)
• Newer — not all libraries support it yet

When to Use Each

The Database Performance Difference

With UUID v4, new records insert at random positions in the B-tree index. This causes page splits and fragmentation — especially painful at scale.

With UUID v7, new records always insert at the end of the index (like auto-increment). This means sequential writes, no page splits, and much better write performance.

Benchmarks show UUID v7 primary keys can be 2-3x faster for write-heavy workloads compared to UUID v4.

Generate UUIDs Now

Need UUIDs quickly? Use our [free UUID generator](/tools/uuid-generator). Generate up to 100 at a time in standard, uppercase, or no-dash format.

UUIDs in Error Tracking

Every error event in Bugsly gets a UUID v7 event ID — time-sortable so you can correlate events chronologically across services. When you're debugging a distributed system and need to trace an error across microservices, time-ordered IDs make the timeline obvious. [Start tracking](/signup).