Java UUID Generator

Generating UUIDs in Java

• UUID.randomUUID() is a static factory that uses a cryptographically strong pseudo-random generator, so the value is suitable for tokens as well as keys. UUID is immutable and toString() always emits the canonical 8-4-4-4-12 lowercase form; UUID.fromString() parses it back and throws IllegalArgumentException on malformed input.
• The JDK has no version 7. For time-ordered keys in a JPA or Hibernate schema, add a library — com.fasterxml.uuid:java-uuid-generator or uuid-creator — or let the database do it. That matters at scale, because a random v4 primary key scatters B-tree inserts across the whole index.

How to generate

1. Press Generate UUID above to mint a value in this browser — nothing is sent anywhere.
2. Copy one value with Copy, or set How many and use Copy all for a fixture list.
3. Switch Version if your code needs v7 instead of the v4 default, and turn on Formatting to match your stack's conventions.

Use Cases

• Hibernate and JPA entity keys — assign in the constructor or with @GeneratedValue removed.
• Correlation IDs in MDC so every log line for a request can be grepped by one value.
• Idempotency tokens for message consumers that must ignore duplicate deliveries.

How Java UUID Generator Compares

Code Examples

import java.util.UUID;

UUID id = UUID.randomUUID();        // v4
System.out.println(id);             // 6b3f0c1e-9a4d-4e2b-8f77-2c1d5a6b7c8d
System.out.println(id.toString());  // same, canonical lowercase

// v7 is not in the JDK — add com.fasterxml.uuid:java-uuid-generator
// UUID v7 = Generators.timeBasedEpochGenerator().generate();

public static boolean isUuid(String s) {
    try {
        UUID.fromString(s);
        return true;
    } catch (IllegalArgumentException e) {
        return false;
    }
}

Frequently Asked Questions

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