Generate cryptographically-random RFC 4122 v4 UUIDs. 100% local — no server calls.
UUIDs are generated locally using the browser's cryptographic random number generator (crypto.getRandomValues). No data is uploaded — everything runs in your browser. Generated UUIDs are collision-resistant for practical use but should not be treated as cryptographically authenticated identifiers.
A v4 UUID is 122 random bits plus 6 fixed bits, written as 32 hex characters in 5 groups. The version (4) says "made of randomness"; the variant (10xx) says "RFC 4122". Everything else is cryptographically random.
Groups are 8-4-4-4-12 hex chars. Only the version nibble (position 19) and variant bits (position 20) are fixed — all other 122 bits are drawn from crypto.getRandomValues.
The same two positions are always meaningful; the rest is noise.
To use it: open the tool, enter your inputs, and get instant results — generate up to 100 UUID v4 values at once. Everything runs locally; nothing is uploaded.
FreeToolHub UUID v4 Generator is a free browser-based tool — generate up to 100 UUID v4 values at once. No signup, no upload; everything runs locally in your browser.
Generate cryptographically secure UUID v4s in bulk, instant and free. RFC 4122 compliant.
This generator produces RFC 4122-compliant version 4 UUIDs — the 128-bit random identifiers like 3f8a1c2e-9b4d-4e6f-8a1b-2c3d4e5f6a7b that databases, APIs, and distributed systems use as collision-proof keys. Randomness comes from the browser's cryptographic number source, the same underlying generator used for security tokens, not a predictable pseudorandom seed. Bulk mode emits up to 100 UUIDs in one click, with uppercase, braces, and no-hyphen formatting toggles for pasting into different systems' expected formats.
Backend developers seed test databases and fixture files with realistic primary keys. API designers generate request IDs and idempotency keys when sketching endpoints before code exists. Frontend engineers produce temporary keys for list rendering and optimistic updates. Data teams generate consistent join keys across CSVs being merged. Anyone prototyping distributed logic — where two machines must invent identifiers without coordinating — gets statistically unique values that will not collide even across billions of draws.
(1) Set the quantity, from 1 to 100. (2) Click generate — each UUID draws 122 random bits from crypto.getRandomValues, sets the version and variant bits per RFC 4122, and formats into the canonical 8-4-4-4-12 hex layout. (3) Toggle formatting: uppercase for legacy Windows systems, braces for .NET-style GUIDs, hyphen-free for compact storage or URL use. (4) Copy all or one. Generation is instant and local; no network call is involved and nothing is logged.
Version 4 is pure randomness and the default choice for most systems: with 122 random bits, the chance of any two generated UUIDs colliding is astronomically small — you would need to generate billions per second for centuries to expect one. Version 1 embeds MAC address and timestamp, enabling sorting but leaking the generating machine's identity; v7, increasingly adopted, prefixes a millisecond timestamp so database indexes stay roughly time-ordered, fixing v4's random-index fragmentation on large tables. ULIDs serve the same goal with shorter, sortable output. If your database is small, stick with v4 everywhere; if insert-heavy tables show index bloat, evaluate v7 on the hot paths. This generator focuses on v4 because it remains the interoperable default across Postgres, MySQL, MongoDB, and every major API framework.
UUIDs come in versions, and v4 (pure random) is the right choice for most modern uses: database primary keys, distributed systems where two nodes must generate IDs without coordination, and request tracing. The alternatives earn their keep in narrower cases — v1 embeds a timestamp and MAC address, which sorts chronologically but leaks hardware identity; v5 and v3 derive deterministically from a name via SHA-1 or MD5, useful when the same input must always yield the same ID; v7 combines a timestamp prefix with random tail bits, giving database-friendly sortability without v1's privacy problem. If you are unsure, generate v4: it has no assumptions about your infrastructure, and its 122 random bits make collisions a non-issue at any scale a single generator can reach.
A v4 UUID is a 122-bit random value formatted as 8-4-4-4-12 hex digits with the version and variant bits fixed. This generator uses the Web Crypto API's cryptographically secure random source — the same class of randomness browsers use for TLS keys — not a predictable Math.random() sequence.
Astronomically small. You would need to generate about 2.7 quintillion v4 UUIDs for a 50% chance of one collision. In practice, duplicate detection is unnecessary — treat each UUID as unique and index your database on it directly.
A v4 UUID is unpredictable enough to serve as a low-stakes secret, but it carries no expiry, no signature, and no revocation — proper API keys and session tokens need those properties. Use UUIDs as identifiers; use dedicated auth mechanisms for authentication.
They are the same 128 bits — comparison should be case-insensitive, and most systems normalize to lowercase. The uppercase toggle exists for display conventions; if your database stores UUIDs as a native type, the case never matters at all.
Yes. UUIDs are generated using the Web Crypto API (crypto.getRandomValues), producing RFC 4122 version 4 UUIDs with 122 bits of randomness. The collision probability is approximately 1 in 2^122 (5.3 × 10^36). Generate up to 10,000 UUIDs per batch, formatted as plain, JSON array, or SQL INSERT statements.
Output options include: lowercase/uppercase plain text (one per line), JSON array, JavaScript array, SQL INSERT VALUES, and CSV. Bulk generation of 1,000 UUIDs completes in under 50ms. Each UUID follows the xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx pattern with version 4 and variant 1 bits correctly set.
Why did the fish get bad grades?
No signups, no data sold. The core of every tool is free forever — the optional Pro plan adds batch processing, unlimited downloads, white-label exports and an ad-free experience.
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