Nil UUID Generator - Create Zero-Value UUIDs

What is Nil UUID?

Nil UUID is a special form of UUID where all 128 bits are set to zero. It is represented as:

00000000-0000-0000-0000-000000000000

The Nil UUID serves as a special reserved value in the UUID ecosystem, defined in RFC 4122. It has specific semantic meaning as an "empty" or "null" identifier when a UUID is required but no actual identifier is appropriate.

How Nil UUID works

It is a predefined constant with all 128 bits set to zero
It technically follows the UUID format of 32 hex digits with hyphens in the 8-4-4-4-12 pattern
It has no version or variant bits because all bits are zeros
It is explicitly identified in RFC 4122 as a special case UUID
It can be used as a sentinel value or placeholder in systems that work with UUIDs

Advantages & Considerations

Advantages	Considerations
Universally recognized special value Useful as a default/empty state Easy to check for (all zeros) Consistent sentinel value across systems	Not globally unique (by design) Should never be used as an actual identifier Could be misinterpreted as an error or uninitialized value May require special handling in systems

Nil UUID Structure

Bits	Content
0-127	All zeros (0x00000000000000000000000000000000)

Unlike standard UUIDs that have specific version and variant bits set, the Nil UUID has all bits set to zero, including what would normally be the version and variant bits.

Nil UUID vs. other versions

Version	Based on	Use case	Uniqueness
Nil UUID	Constant (all zeros)	Special value, placeholder	❌ Not unique (by design)
UUID v1	Time + MAC	Time-ordered IDs	✅ Globally unique
UUID v3	Namespace + MD5	Deterministic IDs	✅ Unique per input
UUID v4	Random	Secure random IDs	✅ Statistically unique
UUID v5	Namespace + SHA-1	Deterministic IDs	✅ Unique per input
UUID v6	Time (reordered)	Sortable IDs	✅ Globally unique
UUID v7	Time + random	Sortable IDs	✅ Globally unique

Common Use Cases

Default values: Initial state before a real UUID is assigned
Sentinel values: Special marker in systems requiring UUIDs
Error detection: Indicator of uninitialized or missing UUID
Database placeholders: When a real UUID is pending or not applicable
Root objects: Parent-child relationships where the root has no parent
Special functions: System operations that need a well-known UUID value
Testing: Placeholder value in test environments

Frequently Asked Questions

Is the Nil UUID a valid UUID?

Yes. The Nil UUID is explicitly defined in RFC 4122 as a special case UUID. While it doesn't follow the normal version/variant rules, it is a recognized UUID value with special semantics.

Can I use the Nil UUID as an identifier?

No. You should never use the Nil UUID as an actual identifier. It is a special reserved value meant to represent the absence of a UUID or a default state. Using it as a regular identifier would violate its special purpose.

How do I check if a UUID is the Nil UUID?

Simply compare the UUID to the string "00000000-0000-0000-0000-000000000000" or check if all bits are zero. Most UUID libraries provide a specific function to check for the Nil UUID.

Do all systems recognize the Nil UUID as special?

Not necessarily. While it's defined in the RFC, not all systems may give it special treatment. Some databases might allow it as a valid value, while others might reject it or give it special semantics.

Is there a difference between Nil UUID and an empty UUID?

In properly implemented systems, "Nil UUID" and "empty UUID" should refer to the same concept: the all-zeros UUID. However, some systems might have different representations for "empty" vs. "nil", so it's important to check the specific implementation.