UUID Generator

Generate UUIDs Online

A UUID (universally unique identifier) is a 128-bit label used to identify resources without a central authority. UUID v4 generates fully random IDs, while v7 embeds a millisecond timestamp so IDs sort chronologically, which is critical for database primary keys. Generate either version here.

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. UUIDs are designed to be unique across space and time, meaning no two UUIDs should ever be the same, even when generated by different people on different computers at different times. They are defined by RFC 9562 and are used extensively in databases, distributed systems, APIs, and software development. A UUID looks like this: 550e8400-e29b-41d4-a716-446655440000. The most common version is UUID v4, which generates completely random values. A newer version, UUID v7, embeds a timestamp in the first 48 bits, making UUIDs sortable by creation time while still being unique.

How to Use

1. Select a version: UUID v4 for random IDs, UUID v7 for time sortable IDs
2. Set quantity: Generate 1 to 1,000 UUIDs at once
3. Click Generate or press Enter
4. Copy individual UUIDs or use Copy All

UUID Formats Explained

UUID v4 (Random)

The most commonly used UUID version. All 122 bits not reserved for version and variant markers are randomly generated using the browser’s cryptographic random number generator (crypto.randomUUID()). Format: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where 4 indicates version 4 and y is one of 8, 9, a, or b (variant bits).

UUID v7 (Time Ordered)

A newer format defined in RFC 9562. The first 48 bits encode a Unix timestamp in milliseconds, followed by random bits. This makes v7 UUIDs naturally sortable by creation time, which is ideal for database primary keys where index locality matters. Format: tttttttt-tttt-7xxx-yxxx-xxxxxxxxxxxx where the t positions encode the timestamp.

Common Use Cases

UUIDs are used as database primary keys, distributed system identifiers, session tokens, correlation IDs for request tracing, and unique filenames or resource identifiers. They allow independent systems to generate unique IDs without coordination.

UUID v7 encodes a Unix millisecond timestamp in its first 48 bits. Use the Unix Timestamp Converter to inspect what date a v7 UUID encodes. If you need an identifier derived from the content instead of a random one, a SHA-256 hash of the content gives you a deterministic, collision resistant ID. Need random strings that aren’t UUID format? The Random String Generator creates custom-length tokens. Generating passwords instead? The Password Generator creates secure random passwords. Have JSON data that needs formatting? The JSON Formatter pretty-prints it. For a detailed comparison of v4 vs v7 bit layout, B-tree performance, and when to use each, see UUID v4 vs v7.