UUIDs generator
A Universally Unique Identifier (UUID) is a 128-bit number used to identify information in computer systems. The number of possible UUIDs is 16^32, which is 2^128 or about 3.4x10^38 (which is a lot!).
About UUIDs generator
A UUID is a 128-bit identifier designed so that separate systems can each mint their own without coordination and still practically never collide. They are common as database keys, request identifiers and generated file names.
When you would use it
- Producing primary keys, especially when the ID must exist before the row is written.
- Generating request or trace identifiers so a single request can be followed across distributed logs.
- Creating temporary file names or upload identifiers that will not clash.
How to use it
- Choose the version you need; v4 is the default.
- Set how many you want; they are generated as you change the options.
- Press Ctrl+Enter to generate a fresh batch.
Things worth knowing
- v4 is fully random and is the right default for almost every use.
- v1 embeds a timestamp and a network card address, so it sorts by time but leaks when and where it was generated.
- v7 also embeds a timestamp, but at the front, so lexicographic order matches time order. That is much friendlier to database indexes than v4 and is the current recommendation.
- Values come from the browser cryptographic random source; nothing is requested from a server.
Frequently asked questions
- Can UUIDs really never collide?
- v4 carries 122 random bits. Even generating a billion per second, a collision would take decades of output to become likely, so in practice you can treat them as unique.
- Do UUID primary keys hurt database performance?
- They can, especially v4. Random values make B-tree indexes split constantly, which costs write throughput and index size compared with an incrementing integer. Use v7 if this matters: its time prefix keeps new rows at the end of the index.