UUIDv4 vs UUIDv7: A Comprehensive Comparison

UUIDv4 vs UUIDv7: A Comprehensive Comparison


4 min read

Universally Unique Identifiers (UUIDs) are widely used in distributed systems to ensure unique identification of objects, avoiding collisions across different databases and systems. Among the various versions of UUIDs, UUIDv4 and the newer UUIDv7 stand out due to their distinct characteristics and use cases. This article provides a detailed comparison of UUIDv4 and UUIDv7, highlighting their features, advantages, and potential drawbacks.

What is UUIDv4?

UUIDv4 is one of the most commonly used versions of UUIDs. It generates 128-bit identifiers using random numbers. Here’s a quick breakdown of its structure:

  • Randomness (122 bits): Most of the bits in a UUIDv4 are randomly generated.

  • Version and Variant bits (6 bits): These bits indicate the UUID version (4 bits) and variant (2 bits).

Advantages of UUIDv4

  1. Simplicity: UUIDv4 is straightforward to generate since it relies solely on randomness. This simplicity makes it easy to implement and use.

  2. High Entropy: With 122 bits of randomness, the likelihood of collision is extremely low, ensuring a high degree of uniqueness.

  3. No Dependency on External Factors: UUIDv4 generation does not rely on external systems or timestamps, making it independent of system clock accuracy.

Disadvantages of UUIDv4

  1. No Ordering: Since UUIDv4 is purely random, there is no inherent ordering. This can lead to fragmentation in databases and less efficient indexing.

  2. Predictability Risk: If the random number generator is not secure, UUIDv4 can become predictable, leading to potential security issues.

What is UUIDv7?

UUIDv7 is a newer version defined in a draft RFC. It introduces a time-based approach to UUID generation, incorporating a timestamp while still maintaining randomness.

Structure of UUIDv7

  • Timestamp (48 bits): Represents the number of milliseconds since the Unix epoch (January 1, 1970).

  • Randomness (80 bits): Ensures uniqueness even if multiple UUIDs are generated at the same millisecond.

Advantages of UUIDv7

  1. Monotonicity: The inclusion of a timestamp ensures that UUIDs are chronologically ordered, improving database indexing and query performance.

  2. Unique Across Distributed Systems: By combining time-based and random components, UUIDv7 maintains high uniqueness.

  3. Compatibility: Follows the 128-bit structure and hexadecimal representation, making it easy to integrate into existing systems.

  4. Debugging and Auditing: The timestamp can be parsed to determine the creation time, aiding in debugging and auditing processes.

Disadvantages of UUIDv7

  1. Dependency on Accurate Timekeeping: Relies on system clocks being accurately synchronized. Time discrepancies can result in out-of-order or duplicate UUIDs.

  2. Potential Privacy Concerns: Embedding the timestamp can expose creation times, which might be undesirable in certain use cases.

  3. Increased Complexity: Generating UUIDv7 requires handling both timestamps and randomness, adding complexity to the implementation.

UUIDv4 vs UUIDv7: Head-to-Head Comparison

Generation MethodRandom number generationTimestamp + Random number generation
OrderNone (purely random)Chronologically ordered
UniquenessHigh (122 bits of randomness)High (48-bit timestamp + 80 bits randomness)
ComplexitySimpleMore complex
DependencyNoneAccurate system clock
Use CasesGeneral-purpose unique identifiersDatabases, distributed systems, event logs
PrivacyNo inherent time dataTimestamp may expose creation time
Indexing PerformancePotentially fragmented due to randomnessImproved due to chronological order

Use Cases

When to Use UUIDv4

  • General-Purpose Identification: Suitable for applications where unique identification is needed, and ordering is not a priority.

  • High-Throughput Systems: Ideal for systems where simplicity and speed of UUID generation are critical.

  • Security-Sensitive Applications: Beneficial when using a secure random number generator to ensure UUID unpredictability.

When to Use UUIDv7

  • Database Systems: Where ordered UUIDs can enhance indexing and query performance.

  • Distributed Systems: Where unique and ordered identifiers across different nodes are required.

  • Event Sourcing and Logging: Where chronological order and uniqueness are essential for tracking events.


Both UUIDv4 and UUIDv7 offer unique advantages tailored to different use cases. UUIDv4 is simple, purely random, and easy to implement, making it suitable for a wide range of applications. UUIDv7, on the other hand, introduces time-based ordering, which can significantly improve performance in certain systems but comes with additional complexity and dependencies. Understanding the strengths and limitations of each version will help you choose the right UUID version for your specific needs.