A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information. Also called GUID (Globally Unique Identifier) in Microsoft systems. The standard format is 8-4-4-4-12 hex characters separated by dashes.

Which UUID version should I use?

Use v4 (random) for most cases. Use v1 when you need timestamp ordering (note: it exposes your MAC address). Use v5 (SHA-1) or v3 (MD5) when you need deterministic IDs from a name.

How do I generate UUIDs in Python?

Use the built-in uuid module: uuid.uuid4() for random, uuid.uuid1() for timestamp-based, uuid.uuid5(namespace, name) for deterministic SHA-1, uuid.uuid3(namespace, name) for deterministic MD5.

UUID vs ULID vs NanoID?

UUID is the standard (RFC 4122), universally supported. ULID is sortable and Crockford-base32 encoded. NanoID is shorter and URL-safe. For most backend work, UUID v4 is the safe default.

Are UUIDs sequential?

v4 UUIDs are completely random. v1 UUIDs contain a timestamp and are roughly sequential. UUIDv7 is specifically designed for sortable, timestamp-ordered IDs.

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UUID / GUID Bulk Generator

Generate UUIDs with format options and matching Python code. Export as JSON, CSV, SQL, or Python list.

UUID Version

Count

Format

Ctrl+G

Generated UUIDs (0)

Python Code

import uuid

# Generate 10 random UUIDs (version 4)
uuids = [str(uuid.uuid4()) for _ in range(10)]

for u in uuids:
    print(u)

How unique are UUIDs?

UUID v4 has 122 random bits (2¹²² possible values = 5.3 × 10³⁶). By the birthday paradox, you'd need to generate 2.71 × 10¹⁸ UUIDs for a 50% chance of one collision. If you generated 1 billion UUIDs per second, it would take ~86 years to reach that threshold.

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