A UUID (Universally Unique Identifier) is a 128-bit number used to label entities in distributed systems without coordination. Properly generated, the chance of two random UUIDs colliding is so low that you can treat collision as impossible for practical purposes. PDFFlare's UUID generator emits standards-compliant identifiers per RFC 4122 and RFC 9562.

Which UUID version should I use?

For most cases use v4 — 122 bits of cryptographic randomness, no metadata leakage, supported everywhere. For database primary keys use v7 — it's time-ordered so it gives much better B-tree index locality than v4 (RFC 9562). For deterministic IDs derived from a known name (e.g., a domain name), use v5. Avoid v3 (MD5-based) for new systems unless you must match a legacy schema.

What's the difference between v4 and v7?

Both are random-feeling, but v7 starts with a 48-bit Unix-millisecond timestamp followed by 74 bits of randomness. The timestamp prefix means v7 UUIDs sort chronologically — critical for database performance because rows inserted in time order land near each other in the B-tree, dramatically reducing page splits and improving cache hit rates. v4 is fully random, so each insert lands in a random spot.

Are these UUIDs cryptographically random?

Yes. PDFFlare's UUID generator uses crypto.getRandomValues() — the browser's CSPRNG — for every random byte. We never use Math.random() (which is predictable). v4 has 122 bits of entropy; even at one billion UUIDs per second, you'd need ~85 years to expect a single collision.

Can I generate the same UUID twice with v5?

Yes — that's the whole point of v3 and v5. They're deterministic: the same (namespace UUID, name string) input always produces the same output UUID. Use this when you need stable IDs that downstream systems can derive without coordination — like a UUID for a hostname that any service can compute identically.

Why do v3 and v5 require a namespace?

The namespace is what gives the (namespace, name) pair its meaning. The same name “example.com” under the DNS namespace produces a different UUID than the same name under the URL namespace — both are valid, both are stable. RFC 4122 defines four standard namespaces (DNS, URL, OID, X.500); PDFFlare's UUID generator supports all four plus a custom namespace UUID.

Is the Nil UUID valid?

The Nil UUID (00000000-0000-0000-0000-000000000000) is reserved by RFC 4122 as a sentinel value — it's a valid UUID format but it doesn't identify anything. Use it as a placeholder, an “unset” marker, or an explicit empty value in code. RFC 9562 added a Max UUID (FFFFFFFF-...) for upper-bound use cases like range queries.

Are my generated UUIDs sent to a server?

No. PDFFlare's UUID generator runs entirely in your browser — every byte comes from your own crypto.getRandomValues() call. Nothing uploads, nothing logs. Safe to use for production secrets, internal API request IDs, and anything else you'd rather not paste into a third-party service.

UUID Generator Online — v1, v4, v7 Bulk Free

UUID generator online — create v1, v4, v5, v7, and Nil/Max UUIDs in bulk. Free, browser-based, copy-friendly. No signup, cryptographically random.

PDFFlare's UUID generator online produces every standards-compliant UUID variant in seconds: v4 (random), v7 (time-ordered for database primary keys), v5 and v3 (deterministic namespace UUIDs), v1 (time-based legacy), plus the Nil and Max sentinel values from RFC 9562. Generate one or one thousand at a time, in five output formats, with cryptographic randomness from your browser's built-in CSPRNG.

Working on the same dev workflow? Pair this with Hash Generator to compute MD5/SHA hashes of arbitrary text, or JWT Decoder to inspect auth tokens that often use UUID-shaped identifiers.

Every UUID is generated locally — your browser's crypto.getRandomValues() provides cryptographically secure randomness for v4 and v7, and crypto.subtle.digest() handles SHA-1 for v5 namespace UUIDs. Nothing uploads, nothing logs. Generate UUIDs for production secrets, internal request IDs, or test fixtures with full confidence.

UUID version

Random — 122 bits of cryptographic randomness. The default for most use cases.

How many UUIDs? (5)

Output format

Which version should I pick?

v4 — random; safe default for most use cases.
v7 — time-ordered; preferred for database primary keys (better index locality, RFC 9562).
v1 — time-based; sortable but leaks timing information. Mostly legacy.
v3 / v5 — deterministic from a (namespace, name) pair. Use when you need stable IDs derived from a known input. Prefer v5 (SHA-1) over v3 (MD5) for new code.
Nil / Max — sentinel values. Not random; useful as placeholders or range bounds.

Generated UUIDs (0)

Configure options on the left — UUIDs appear here.

How to Generate UUIDs

Pick a UUID version
v4 (random) is the safe default. Pick v7 for database primary keys, v5 for deterministic IDs derived from a name, or v1 for time-sortable legacy compatibility.
Set output format and count
Choose hyphenated (default), no-hyphens, UPPERCASE, brace-wrapped, or URL-safe base64. Generate 1-1000 in a single batch.
Generate, copy individual or all
UUIDs regenerate live as you change settings. Copy any individual UUID with one click, or use 'Copy all' to grab the entire list as newline-separated text.

When Do You Need a UUID Generator Online?

Database primary keys (v7): Modern Postgres, MySQL, and MongoDB all benefit from time-ordered UUIDs as primary keys. v7 sorts by creation time, giving B-tree indexes much better locality than fully-random v4 — fewer page splits, faster inserts, better cache hit rates. RFC 9562 made v7 the standard recommendation for new databases.

API request and trace IDs (v4): Every modern API attaches a UUID to incoming requests for correlation across logs, metrics, and traces. v4's pure randomness means no metadata leakage and no central coordinator needed — every service can mint its own without collisions.

Distributed systems (v1 + v7): Sharded systems and multi-region deployments need IDs that don't require a centralized counter. UUIDs let every node generate IDs independently with effectively zero collision risk. v7 is the modern pick; v1 still appears in older systems.

Deterministic IDs (v5): When you need stable IDs derived from a known name (a hostname, an email address, an enum value), v5 with the appropriate namespace gives you a UUID that any service can recompute identically. Used heavily for content addressing, idempotency keys, and stable identifiers in event-driven systems.

Why Choose PDFFlare's UUID Generator Online?

Every Version Supported

v1, v3, v4, v5, v7, plus Nil and Max sentinels from RFC 9562. One tool covers every standards-compliant UUID format.

Bulk Mode (1-1000)

Generate up to 1000 UUIDs in a single batch — perfect for seed data, fixtures, and stress-testing distributed systems.

5 Output Formats

Hyphenated, no-hyphens, UPPERCASE, brace-wrapped (Microsoft), URL-safe base64. Match whatever format your downstream system expects.

100% Browser-Based

Cryptographic randomness via crypto.getRandomValues() — never Math.random(). Your UUIDs never leave your device.

Frequently Asked Questions About UUID Generator

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