What Is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit identifier used to label
records, requests, files and objects without a central coordinator. The standard
text form is 36 characters with hyphens, for example
0b7c3a44-1a6d-4e8e-b6d5-f943fad819dd. Without hyphens the value is 32
characters.
This generator creates version 4 UUIDs, which are based on random data. Each value is produced with the browser's cryptographically secure random generator. You can generate one or many at once, choose uppercase output and remove hyphens.
How to Generate UUIDs
- Choose how many UUIDs you need (1–100).
- Optionally enable uppercase output.
- Optionally keep or remove hyphens.
- Select Generate UUIDs.
- Copy or download the result.
The generator runs locally in your browser. No identifiers are sent to a server.
UUID vs GUID vs Sequential IDs
GUID is Microsoft's name for the same general identifier format. UUIDs are useful when IDs must be generated on the client, across distributed systems or before a database insert. Sequential integer IDs are shorter and often faster to index, but they reveal record counts and require coordination. UUIDs trade some index size and locality for decentralization and unpredictability.
When to Use UUIDs
- Primary keys for records created on the client.
- Idempotency keys and request identifiers.
- Correlation IDs in distributed systems and logs.
- File names and temporary resources.
- Test fixtures and seed data.
UUID Versions
Version 4 UUIDs are random. Version 1 and version 7 UUIDs include time-based components; version 7 is designed to be time-ordered, which can improve database index locality. This tool generates version 4 because it is simple, widely supported and does not require a timestamp or node identifier.
Collision Probability
A version 4 UUID has 122 random bits after reserving bits for the version and variant. The probability of generating the same UUID twice is extremely small, but not mathematically zero. For practical applications, v4 UUIDs are considered unique enough without a central registry.
UUIDs Are Not Secrets
A UUID is unique, but it is not a password, access token or proof of authorization. Do not use a UUID alone to protect a private resource. If an identifier appears in a URL, assume someone can guess or obtain it; enforce authentication and authorization on the server.
Formatting Options
The canonical form uses lowercase hexadecimal with hyphens. Uppercase is accepted by most systems but can be inconvenient for comparisons. Removing hyphens produces a compact 32-character string used by some APIs and databases. Choose the format the receiving system expects and be consistent.
Choosing an Identifier Strategy
The best identifier depends on how it will be stored and exposed. Sequential integers are compact and index well, but they reveal volume and require a central sequence. Random UUIDs can be generated anywhere without coordination, but their randomness can reduce database index locality. Time-ordered identifiers such as UUID v7 or ULID combine uniqueness with better insertion order, at the cost of exposing an approximate creation time.
Use internal numeric IDs for private database keys and public UUIDs for external references when you do not want to expose sequence numbers. Do not treat a public identifier as an authorization check; verify permissions on every request.
Storage and Formatting
Store UUIDs in the canonical hyphenated form unless the database or API requires compact values. Be consistent: mixing uppercase, lowercase and hyphenated forms can create records that look different but represent the same identifier. Index the column appropriately and document which UUID version the system generates.
Privacy
Generation happens locally with the browser's secure random API. No UUIDs, settings or metadata are uploaded. For hashing text into a fingerprint, use the Hash Generator; for time-based values, use the Unix Timestamp Converter.
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