UUID क्या है? Universally Unique Identifiers की संपूर्ण व्याख्या
Quick Answer
UUID 128-bit identifier है जो 36 अक्षरों में दर्शाया जाता है (32 hex अंक और 4 hyphen)। UUID बिना समन्वय के व्यावहारिक रूप से अद्वितीय —collision probability नगण्य। UUID v4 (random) सबसे आम है। हमारे मुफ्त UUID Generator से बनाएँ।
Introduction
UUID (Universally Unique Identifier), Microsoft terminology में GUID (Globally Unique Identifier) भी, 128-bit identifier है जो बिना केंद्रीय समन्वय के व्यावहारिक रूप से अद्वितीय होता है। UUID RFC 4122 द्वारा परिभाषित है और डेटाबेस primary key, request ID, session token और वितरित सिस्टम identifier के रूप में व्यापक उपयोग होता है। सबसे आम संस्करण UUID v4 है जो random bits उपयोग करता है।
Step by Step
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Understand UUID structure
A UUID is 128 bits, displayed as 32 hexadecimal digits in 5 groups: 8-4-4-4-12, separated by hyphens (e.g., 550e8400-e29b-41d4-a716-446655440000). The 13th digit indicates the version (4 for v4), and the 17th digit indicates the variant.
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Learn the UUID versions
v1: time-based (timestamp + MAC address) — time-ordered but leaks identity. v3: name-based with MD5 hashing. v4: random — most common, no privacy concerns. v5: name-based with SHA-1 hashing. v6 and v7: time-ordered with improved privacy over v1.
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Understand collision probability
UUID v4 has 2^122 possible values. The probability of a collision among 103 trillion UUIDs is 50%. For practical use (millions of IDs), the collision probability is effectively zero — you can generate UUIDs independently without coordination.
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Use UUIDs appropriately
Use v4 for almost all use cases (database IDs, request IDs, session tokens). Use v7 if you need time-ordered IDs for database locality. Avoid v1 in security-sensitive contexts — it embeds a timestamp and MAC address.
Examples
UUID v4 (random)
Input: Generated with crypto.getRandomValues
Output: 550e8400-e29b-41d4-a716-446655440000
UUID v1 (time-based)
Input: Timestamp + MAC address
Output: a3bbf0ee-d6e4-11ed-a5b3-3c9703e8b4a1
Nil UUID
Input: All zeros
Output: 00000000-0000-0000-0000-000000000000
Common Problems
- Using Math.random() for UUIDs —it is not cryptographically secure. Use crypto.getRandomValues() or crypto.randomUUID() in browsers.
- Storing UUIDs as strings —a UUID string is 36 bytes; stored as a UUID type (16 bytes) it is more efficient. Use the native UUID type in databases when available.
- Using v1 in security-sensitive contexts —v1 embeds a timestamp and MAC address, which can leak information about when and where it was generated. Use v4 for anonymity.
- Assuming UUIDs are truly unique —they are practically unique (collision probability is negligible), but not mathematically guaranteed unique.
Tips
- Use UUID v4 for almost all use cases —it is random, has no privacy concerns, and is supported by all modern databases.
- Use crypto.randomUUID() in modern browsers for a built-in v4 generator without a library.
- Store UUIDs as UUID/GUID type in databases (16 bytes) instead of strings (36 bytes) for better storage and index performance.
- Use our UUID Generator to create UUIDs instantly in your browser —no signup, fully private.